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Author Topic: MC-8 Manual Trans. Shifting  (Read 4129 times)
DavidInWilmNC
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« on: July 05, 2007, 07:10:15 AM »

When I drive this bus, I usually grind gears during downshifts and occasionally during a downshift.  The fact that I can occasionally shift it smoothly makes me think that it's my 'technique' insteat of a problem with the bus.  I double-clutch every change.  I shift at or right at governed speed.  It feels like the clutch isn't completely disengaged... at least that's how a car I had felt prior to an adjustment.  I've turned the adjustment knob 'til I felt pressure, then backed it off like instructed in the manual.  That helped some, maybe.  The vagueness of 'until pressure is felt' or whatever in the manual doesn't help.  Should it be completely without pressure then any pressure is when one stops turning the knob?  Some shifts are as smooth as my Toyota's automatic, and sometimes I can't get it into gear.  Sometimes, if I'm stopped, it'll grind a bit when put into first or reverse.  I can generally upshift fine to second, have an occasional grind into third, and the shift into fourth is usually smooth.  I believe I'm following the shifting tips posted on the 'other' forum correctly.  I guess I'm wondering how long it generally takes to master shifting these old buses.  Thanks for any tips or suggestions.

David
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« Reply #1 on: July 05, 2007, 09:48:00 AM »

David,

Mostly it just takes experience to learn how the different components should feel at different shift points.

A couple of months ago I broke the shift rods on my bus and had to replace them.

Before I broke them the shifter was stiff but sloppy, so while I had it apart I tightened it up and greased everything.

I was use to the way it shifted before, but now I have to get use to it all over again. The tower is tight and the shifting mechanism is smooth.

All the way from the Flea Market where I fixed it to the state park where we camped I missed probably 75% of the shifts!


Take a look at RJ Longs article on shifting:

http://www.busnut.com/bbs/messages/12262/16204.html?1167073154
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buswarrior
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« Reply #2 on: July 05, 2007, 01:18:55 PM »

Smooth shifting is mostly a matter of timing.

All the internals are changing the speeds they are rotating at, and you are trying to nail the meshing of gears, the sliding of a spline on a shaft, many feet of skinny linkage on both clutch and shifter at pretty much the precise moment that they are spinning at the same speed. That instant passes, as they go from too fast to too slow to engage with one another.

Get it right on, you might wonder if it even went into gear, a little knock is you being close, a rattle is further away.

Former truckers sometimes have trouble with how slow the shift has to be compared to a 10 or more speed tranny due to the great RPM drop between the gears on a 4 or 5 speed bus tranny.

Car drivers, used to synchros, have never had to think about timing, the tranny helped get the gears together for them.

happy coaching!
buswarrior
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DavidInWilmNC
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« Reply #3 on: July 05, 2007, 01:59:19 PM »

There are a couple of things that are strange to me about shifting this bus.  One is that it seems to shift better (less grinding) soon after starting it as opposed to shifting it after running for a few hours.  This could also just be me getting tired of fighting the shifter for a few hours!  Wink  Another thing is that it often grinds a bit putting it into reverse or first when stopped.  It's not a bad grind like trying to fight it into gear, but more like the grinding is slowing the gears down enough to engage.  That makes me think that something isn't adjusted correctly... like the clutch.  How does one tell if the linkage is adjusted properly?  With the clutch in and the engine running or the engine off, it shifts smoothly and seems to drop into gear, making me think that the linkage is o.k.  Other times it engages so smoothly that, like BW says, I wonder if it even went into gear.  Sometimes it grinds a bit but the clutch engages very smoothly, which makes me think that I had the RPM's matched (mostly) correctly.  I can deal with it taking time to get smooth with shifting this transmission, but I worry about damaging it.  If I heard somebody shifting a car or small truck that I owned like this, they wouldn't drive it again!  I can handle shifting cars and motorcycles, and, although entirely different, surely I can master shifting the bus.  Thanks for the input, guys.

David
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DrivingMissLazy
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« Reply #4 on: July 05, 2007, 02:19:06 PM »

David, it is entirely normal for it to shift better when it is cold. The lube in the tranny is thicker and the gears slow down faster.
If you are sitting with the clutch out, the gears in the tranny are spinning. When you push in the clutch to put it in gear, you have to wait for the gears to stop spinning. Many times you can try and slip it into fourth gear first and you will have little gear raking. Then without releasing the clutch, slip it into first or reverse. It should go in without any problem.
Richard

There are a couple of things that are strange to me about shifting this bus.  One is that it seems to shift better (less grinding) soon after starting it as opposed to shifting it after running for a few hours.  This could also just be me getting tired of fighting the shifter for a few hours!  Wink  Another thing is that it often grinds a bit putting it into reverse or first when stopped.  It's not a bad grind like trying to fight it into gear, but more like the grinding is slowing the gears down enough to engage.  That makes me think that something isn't adjusted correctly... like the clutch.  How does one tell if the linkage is adjusted properly?  With the clutch in and the engine running or the engine off, it shifts smoothly and seems to drop into gear, making me think that the linkage is o.k.  Other times it engages so smoothly that, like BW says, I wonder if it even went into gear.  Sometimes it grinds a bit but the clutch engages very smoothly, which makes me think that I had the RPM's matched (mostly) correctly.  I can deal with it taking time to get smooth with shifting this transmission, but I worry about damaging it.  If I heard somebody shifting a car or small truck that I owned like this, they wouldn't drive it again!  I can handle shifting cars and motorcycles, and, although entirely different, surely I can master shifting the bus.  Thanks for the input, guys.

David
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« Reply #5 on: July 05, 2007, 02:27:51 PM »

I know on truck clutches they have a clutch brake that stops the gears from rotating so you can get into gear from neutral without grinding.  It works by depressing the pedal all the way to the floor then push moderately on it to activate the brake.  Not sure if buses have this feature.  One way to tell if the clutch is adjusted right is to push the clutch all the way in and get it in gear.  Then with the clutch pedal still pushed on the floor, put it into neutral for a second or two then put it back into gear (don't let up on the clutch).  If it grinds alot, the clutch is dragging.  If you get just a couple of bump grinds, then it is adjusted right.  Technically the transmission should shift easier when warm since everything will be loosened up.  The fore mentioned cold oil slowing things down could be a factor in cold shifting ease.  When shifting, make sure you push the clutch pedal all the way to the floor or else you might drag the clutch which will make shifting more difficult.  Good Luck, TomC
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« Reply #6 on: July 05, 2007, 02:32:12 PM »

My 4104 always shifted better when I first started out and when the tranny was cold. I always assumed it was due to the thicker oil.
Richard

I know on truck clutches they have a clutch brake that stops the gears from rotating so you can get into gear from neutral without grinding.  It works by depressing the pedal all the way to the floor then push moderately on it to activate the brake.  Not sure if buses have this feature.  One way to tell if the clutch is adjusted right is to push the clutch all the way in and get it in gear.  Then with the clutch pedal still pushed on the floor, put it into neutral for a second or two then put it back into gear (don't let up on the clutch).  If it grinds alot, the clutch is dragging.  If you get just a couple of bump grinds, then it is adjusted right.  Technically the transmission should shift easier when warm since everything will be loosened up.  The fore mentioned cold oil slowing things down could be a factor in cold shifting ease.  When shifting, make sure you push the clutch pedal all the way to the floor or else you might drag the clutch which will make shifting more difficult.  Good Luck, TomC
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« Reply #7 on: July 05, 2007, 05:22:18 PM »

David all the things said above are true! First of all I applaud you and anyone else who can double clutch properly! I have owned and driven semi-trucks, buses and just about everything else with manual transmissions all my teen & adult life and have never been able to successfully double clutch any of them! I have always had better luck with a single push on the clutch or simply floating the gears altogether with out using the clutch for anything except 1st and reverse! I have tried many time to get the hang of it but never been able too! And I've even had a company I leased a truck to once send their shop foreman out with me for a road test in my truck. And he got upset with me because I could perfectly and smoothly float the gears, but not double clutch with out grinding the heck out of them! I asked him what difference it made since A) it was MY TRUCK, and B) because I could shift perfectly the other 2 ways ! His response was "We want all our drivers to double clutch our trucks, and if your truck ever breaks down and we rent you 1 of ours til yours is back on the road, I want you too be able to shift it my way!" Well after about 15 minutes of trying to show me how he gave up, and told me "just shift the way you know how, because you do a fine job of it that way! LOL"! When we got back to the office the company owner asked him "well is he good to go?" and his response was "yeah, but let him shift his way and don't ask me why!"
Anyway after I got outta trucking and into buses my uncle tried to get me to double clutch and eventually came to the same conclusion and told me "do it your way! I won't have to replace any tranny's or clutches that way"!

Bottom line is if you can double clutch, do it! But there are ways that work better for others!

Anyway if you have time this coming week you ought to look up my dad! The reason I say to look up my dad, although he may be a little rusty/outta practice but he has always been able to shift a manual transmission bus better than anybody else I seen! He might have time to give you some pointers!
I can't guarantee that though as he's hauling the CIA some of our regular customers. And from what he tells me they keep him hoping! The CIA (in this case is  Christians In Action, a youth group that performs at different churchs, senior homes, youth group homes, and such as they travel. And in return they get a meals, or place to stay.)
He'll be in Wilmington Tuesday thru Thursday 7/9-12/07 I don't know the exact times but he will be at or around St. Matthews Lutheran Church @ 612 South College Rd, Wilmington, NC. The group will be staying there at night in their Family Life Center. Call me if you'd like to get dads #, or if you'd like to catch one of the CIA's shows! FWIW! BK

PS I wanted to drive this trip, but this group specifically requests mom & dad!
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Busted Knuckle aka Bryce Gaston
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« Reply #8 on: July 05, 2007, 06:01:14 PM »

You can't hurt your trans. if you don't force it. Just use your fingers, lightly. Grinding going into 1st and r. is normal. Don't force it. It just takes miles to get good at it. Back in the seventies, driving every day for a living, I could shift those 4 speeds without looking at the speedo at any rpm really smoothly. Now, getting out only once in a while, it takes a few miles to get the hang of it.
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JC
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« Reply #9 on: July 05, 2007, 09:52:43 PM »

I do pretty much the same as BK, I only use the clutch for first gear when starting from a dead stop. I, too, found that I didn't shift any better using the clutch, double or not, than with no clutch at all in both directions so why wear out the clutch??

I have the same problem as you when stopped. It is easier for me to just stop the engine, shift into first and restart than to wait for the gears to stop. When I roll up to a stop sign I push in the clutch and gently drop it into first with no grinding. You must be almost stopped to do this. When I can I stop on a slight incline and then can leave it in neutral and let it roll slightly when ready to shift into first, it doesn't take much.

On my Spicer 4-sp there is no grinding going from first to reverse when stopped or when going back to first from reverse. Once you get it into first you have it made.

It takes a bit of practice and patience between gears going up but going down needs to be quicker. I usually just hold down the throttle a bit in neutral when going down and it slips right into gear. Sometimes not!!

When shifting without the clutch you must back off the throttle before taking it out of gear in both directions, this unloads the gears.

I never have a day of all perfect shifts. I've driven a bunch of trucks, including 18 wheelers, and none of them are as  hard to shift as my bus.
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PD4107-152
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« Reply #10 on: July 05, 2007, 10:05:49 PM »


I believe I'm following the shifting tips posted on the 'other' forum correctly.  I guess I'm wondering how long it generally takes to master shifting these old buses.
 

Since I wrote that article on BNO you're talking about, I'll share that, IBME, that it takes anywhere from 3,000 - 5,000 miles of experience before you can hit your shift points, both up and down, 95% of the time w/o bumping a gear.

IF you've got the touch.  Some folk never seem to master double-clutching (BK admits to it!), yet can drive them extremely smoothly w/o a lot of grinding.  For others, it comes quickly - my son, when he was 16, figured out upshifting our 4106 easily, but nine years later, he still bumps the gears on downshifts - which is the more difficult of the two.

An awful lot is "feel" and knowing your coach.

No wonder automatics are so popular, eh?

FWIW & HTH. . .

 Wink
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RJ Long
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DavidInWilmNC
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« Reply #11 on: July 06, 2007, 05:12:26 AM »

Actually, I don't really care whether or not I use the clutch just as long as I don't grind the gears!  I haven't tried shifting w/out the clutch, although I have done it in cars and on my bike (motorcycle).  If it takes 3,000+ miles to 'master' shifting, I guess I'm not doing so badly.  I can up-shift fairly smoothly about 60% of the time, very smoothly (like my car's automatic) maybe 15% of the time, and rough as hell the remaining 25%.  I'm able to start, get up to speed, make turns, stop, and manage to up- and down-shift functionally.  It mainly bothers others riding with me, as they think something is wrong with the bus.  I'm not sure that they'll feel any better knowing the problem isn't the bus but is me instead!   Wink

I probably would have bought an automatic, but I think I got a decent deal on this bus.  The exterior is in very good shape, except for the damage I did on those roots, the tires are decent, and the engine was rebuilt 30,000 miles ago and runs great.  I certainly understand why some would wait and pay more for the good condition of this one plus a good automatic. 

Thanks for all the comments.  I don't feel so bad about it now.

David
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« Reply #12 on: July 06, 2007, 08:33:07 AM »

You'll do fine as soon as you find YOUR groove!
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Busted Knuckle aka Bryce Gaston
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« Reply #13 on: July 06, 2007, 08:55:58 AM »

David- the nice thing is all is repairable.  You're close encounter with the roots will be a bit laborious to repair, but I'm confident it won't happen quite as easily next time.
Shifting is a pain (this from a truck driver that drove nothing but 13spds and for 1.3 million miles).  Maybe somewhere down the road you'll want to change to an Allison.  I was personally ruined when in 1982 I went to a Detroit Diesel/Allison (when they were still together) ride and drive at the Rose Bowl here in L.A.  I drove a Kenworth with a 500hp 8V-92TA DDEC and a 5 spd HT755CR ATEC with the truck loaded to about 67,000lb.  It felt more like driving a pickup pulling a big Airstream behind than a truck.  From that day forward, always lusted for an Allison in my truck.  In fact before I became a new truck salesman at Los Angeles Freightliner, I had a Freightliner Argosy (cabover) with a small sleeper (101" cab) all spec'ed with a 430/470 Series 60 and the HD4060 Allison with a long wheelbase to facilitate a 12ft drom box that would have been converted into a sleeper.  But I smartly did not ultimately order it.  Would have been fun though out accelerating all the trucks, even loaded, from the signals. 
Enjoy your bus-they're absolutely the best way to travel!  Good Luck, TomC
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Tom & Donna Christman. '77 AMGeneral 10240B; 8V-71TATAIC V730.
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« Reply #14 on: July 06, 2007, 07:16:08 PM »

I agree with most that has been posted here. I have driven the old International  549 gas engines with 5 speed main and 3 speed auxiliary, Mack triplexes (3 transmissions, 3 sticks), 5, 6, 9, and 10 speeds, 10 over, 10 under, 15 over and under, 15 double over and some autos; and, this Spicer 4 speed in my MC7 is the orneriest  transmission I have ever tried to shift in my life!  Before I got it, I prided myself on smooth shifting. Now I am thankful to get it in a gear. I drove a lot with my Father and other family members whose favorite expressions were "When you shift, I don't want to feel anything except the change in the engine!" and "If you can't shift it right, I CAN, & you can GET OUT right HERE!"   Angry I am afriad if Dad was with me now, I would be left standing on the side of the road!  Embarrassed

But I'm working on it, and I believe I will get it right before I lose the tranny.  Grin
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DavidInWilmNC
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« Reply #15 on: July 06, 2007, 07:38:18 PM »

But I'm working on it, and I believe I will get it right before I lose the tranny.  Grin

That's exactly what I'm hoping for.  That and hoping those riding with me don't lose confidence in me and the bus!  I'm curious if the other manual transmissions (5-speed MC-9's, etc) are all as difficult to shift smoothly.  The first time I drove it going to Timmonsville was a bit ... strange (for lack of a better word).  I tried to down-shift into 2nd, and I swear it felt like the transmission smacked my hand with the shifter as if to say "NO!"  It was scary.

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« Reply #16 on: July 06, 2007, 08:21:03 PM »

David,

You will find that shifting heavy truck trans w/out clutch is easier than a car or bike. So is the bus except that it is so hard to do smoothly, but no worse than with the clutch.

The only time I miss an AT is in close quarters, starting on a hill and in heavy traffic. I have two fire trucks with AT and they are easy to drive, especially when backing them into the close quarters of my buildings.

If anyone ever comments on my shifting in the bus I always offer them a try at it. So far there have been no takers and my wife and I cheer every time I have a good day of shifting. It is definitely a challenge and keeps you on your toes.

I'm convinced that the real problem is the long, flexible shifting rods and many rod/lever connections-there must be a dozen of them for each rod.

I completely overhauled my shift and clutch linkages-new rod ends and pins-much hard labor. It is a lot better, especially the clutch, but the shifting is still difficult. I just adjusted the 1-2 rod yesterday, they demand constant adjustment.
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« Reply #17 on: July 06, 2007, 08:23:46 PM »

Quote from: DavidInWilmNC
I'm curious if the other manual transmissions (5-speed MC-9's, etc) are all as difficult to shift smoothly. 

YES!

Quote from: DavidInWilmNC
The first time I drove it going to Timmonsville was a bit ... strange (for lack of a better word).  I tried to down-shift into 2nd, and I swear it felt like the transmission smacked my hand with the shifter as if to say "NO!"  It was scary.

Better for it to smack your hand than to "go off on you!" Ya know like KABOOOM!!!
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Busted Knuckle aka Bryce Gaston
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« Reply #18 on: July 06, 2007, 10:18:35 PM »

<I tried to down-shift into 2nd, and I swear it felt like the transmission smacked my hand with the shifter as if to say "NO!">

That was because you only had it part of the way into gear. When torque was applied it popped out of gear.  Or there was quite a bit of difference in gear speeds and it 'bounced' backed when it caught the edges.  Not a good thing to do to much.  You will learn to 'feel' the gear sliders just bumping each other with practice just before they match speeds.

Try to keep pressure on the shifter until you are sure its in all the way.  That is, keep pressure on until full torque either speeding up or holding back is applied.  Try to get in the habit of reapplying throttle or, letting off if down shifting, slowly.  There is an instant when there is no torgue as you reapply throttle or let off if down shifting which will let it go all the way into gear if it was only partially in.   Also a quick blip of throttle with pressure on the shift lever will make sure it is in all the way.  Works up shifting or down shifting. 

Clear as mud? 

My old bus has one gear that it does not like to stay in when going down hill.  Never comes out unless holding back against the engine.  I just have to remember to blip the throttle and pull it back in once in a while on long down hills.  More that likely a result of popping out when only partially engaged too many times. 

Remember, it it feels like it did not go into gear just right, blip the throttle slowly with pressure on the shifter.  You will feel if it goes the rest of the way into gear.

As they used to say, grind a pound for me.  Smiley
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Don 4107 Eastern Washington
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« Reply #19 on: July 07, 2007, 03:16:20 AM »

Don't worry David,

Next year they are coming out with an upgrade to the spicer 4 speed transmission.

I hear the gears are made out of water so all you have to do is pour them in!   Roll Eyes Roll Eyes Roll Eyes Roll Eyes

I still think I like the Road ranger gear upgrade better... they are made from rubber so you can erase your mistakes!  Grin Grin

Sorry, I tried to resist, I really did!

Dallas
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« Reply #20 on: July 07, 2007, 05:58:23 AM »

I hope you do not have an air throttle. I tried driving one one time with an air throttle and absolutely could not get a good shift when going down in gears. Also, a tach would be a great investment.
Richard
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« Reply #21 on: July 09, 2007, 02:44:53 AM »

"One is that it seems to shift better (less grinding) soon after starting it as opposed to shifting it after running for a few hours."

Possibly indicates a need to slow down the timing once the oil has warmed up and the gears spin more freely and take longer to slow down.
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« Reply #22 on: July 09, 2007, 04:09:44 AM »


 I'm curious if the other manual transmissions (5-speed MC-9's, etc) are all as difficult to shift smoothly. 


I've been reading your posts with interest because I also have worries about the manual gearchange on my bus. I think the type of transmission must make a difference because I have never 'ground' the gears in mine (it is a syncromesh 'box), but I sometimes struggle to get it into gear; 95% of the problem I have is when changing into 2nd, and I'm not sure if it is an 'engine speed' thing, or whether I cannot physically find the gate. I suspect the latter, as the change from 1st-to-2nd happens at a very low road speed, and I think my problems stem from the fact that I always try to rush the change in an effort to maintain momentum. I imagine a non-syncro 'box that requires a double-declutch on the 1st-to-2nd change must be a nightmare, especially when pulling away from a standstill on a hill.

Downchanges from 3rd-to-2nd always worry me a bit as well, although at least you have a bit more time to make the change then. Changes from 2nd-to-1st I usually avoid altogther by braking to a stop, then selecting first when stationary.

I would like to understand more about how to judge the engine speed correctly when shifting gears - maybe I could benefit from fitting a tach to help me learn this, as the idea of running the engine up against the governer each time seems completely wrong to me - Screaming an engine in any vehicle goes entirely against my instincts, and I'm sure I've never had my bus engine against it's governer in the whole time I've had it - but then I've never been trained to drive big diesels, and it may well be that that is how they're designed to be used.

Jeremy
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« Reply #23 on: July 09, 2007, 05:20:24 AM »

Jeremy,

If you have a 'synchromesh' transmission, I'd think that you'd have a much easier time changing gears.  From my understanding, worn synchronizers can make gears grind, too.  It's not too much of a nightmare, except when I've gotten it in neutral and can't get it into any gear!  Pulling away from a stop on a hill with a car close behind me is a bit unsetteling, but not to bad.  Since I do the DTS as described in the 'how to shift' post on the 'other' forum, I just keep my foot on the brake 'til I feel the engine pulling a bit, let up off the brake, and step on the throttle.  If nobody is behind me, I'll just start as normal.  One thing about these buses, they will roll at the slightest incline.  Perhaps your linkage needs some adjustment.

David
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Dallas
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« Reply #24 on: July 09, 2007, 05:37:49 AM »

Jeremy,
2 things come to mind with your setup.

The first is, since it's a syncro transmission, and the 1-2 gear ratio is extremely close, I would believe it's possible 1st gear is a deep reduction gear and as such should only be used when starting on a hill or pulling a heavy load. This means you should be able to start out in 2nd gear without doing damage to the clutch.

Most Heavy trucks in North and South America are set up this way, as well as Volvo, Bedford and Scania trucks around the world. I can't say for sure about other makes.

Try starting out in 2nd and see if you can do it without slipping the clutch or using the accelerator. If so, you should be safe doing it all the time. Check the operators manual for that transmission, whoever the maker is.

The next thing is, I believe your engine is a 4 stroke/cycle engine and it reaches it's maximum torque at a much lower RPM than our 2 stroke/cycle Detroit Dinosaurs which don't hit the peak torque until around 1900 rpm.
You won't need to run it against the governor since it's possible that your engine, like our Caterpillar, Cummins and Detroit 4 Stroke/cycle engines reach maximum torque as low as 1100 rpm and level off at around 1500 rpm, (IIRC).

By the way, as an aside, does Bedford still build engines in the UK? and if so, do they still make the Detroit based 2 stroke/cycle that was popular in the 50's, 60's and 70's?

Dallas
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« Reply #25 on: July 09, 2007, 05:42:34 AM »

"One is that it seems to shift better (less grinding) soon after starting it as opposed to shifting it after running for a few hours."

Possibly indicates a need to slow down the timing once the oil has warmed up and the gears spin more freely and take longer to slow down.

Thanks for pointing out what I'm sure is a big part of the problem. it's so obvious that I must often overlook that aspect of shiftting and will make a more conscious effort to give the gears some time to slow down.  I wonder if a heavier weight oil in the transmission would help slow those pesky gears down?  Wink I'll change the fluid in the near future and see if any chunks of gears fall out from all the grinding. My dip stick is missing, so now would be a good time to take care of that.

David
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« Reply #26 on: July 09, 2007, 06:56:27 AM »

Hi Dallas

Thanks for your post - you've put my mind at rest about a couple of things there. Firstly, 1st gear on mine is extremely low - as soon as the bus starts to roll you need to change up. In fact, when I first took posession of the bus the guy was delivered it to my house took me for a quick drive and demonstrated, amongst other things, shifting each gear from first up to fourth. "Hang On" I said, "it's supposed to have five gears". "Oh" he says, and has a fiddle with the gear lever and finds 1st for the first time.

But then, when I took the bus to a local HGV mechanic to have it inspected / tested, he said to use 1st every time, no matter how low it was, because he said that in something as heavy as a bus it is much easier to burn a clutch out than in a car - so that's what I've been doing, but I've always felt that it would be perfectly happy setting off in 2nd when on flat ground.

So, I'll switch to starting in 2nd in normal circumstances, which will also have the happy side-effect of avoiding the 1st-2nd change, which is the only one I tend to have any problems with.

Your point about 4-strokes not needing to be reved makes sense as well, so I'm glad my 'softly softly' approach on the accelerator pedal is ok (as an aside, I've always much prefered big cars with big torquey V8s or diesel engines, rather than small ones with revvy 4-cylinders'. Whether it's the sound or what I don't know, but for some reason I have always hated having to make engines spin quickly).

Lastly, to answer your question, Bedford sadly no longer makes any heavy commercial vehicles - in fact my bus was apparently one the last batch of seven coach chassis they made. The factory still builds vans, but GM badge them as Vauxhalls now (Vauxhall being GM's main car brand in the UK, similar to Chevy).

Jeremy
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« Reply #27 on: July 09, 2007, 07:09:14 AM »

Many years ago when I was involved in driving large vehicles, many, if not most, had what we called a granny low. It was especially useful here in the hills of West (by god) Virginia as there is typically only one way of starting, and that is uphill. LOL Normally not used except when heavily loaded or starting uphill.
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« Reply #28 on: July 09, 2007, 07:27:40 AM »

Jeremy -

A tachometer might be a worthwhile investment for you.  With a tach, you'd be able to determine the rpm splits between each gear, which can be very helpful.

What engine does your Plaxton have?

Running a diesel up to the governor won't hurt them - it's only (usually) 2100 rpm - about what your auto runs on the M1 at 70 mph.

FWIW & HTH. . .

 Wink
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« Reply #29 on: July 09, 2007, 07:58:14 AM »

Jeremy -

A tachometer might be a worthwhile investment for you.  With a tach, you'd be able to determine the rpm splits between each gear, which can be very helpful.

What engine does your Plaxton have?

Running a diesel up to the governor won't hurt them - it's only (usually) 2100 rpm - about what your auto runs on the M1 at 70 mph.

FWIW & HTH. . .

 Wink

Actually, I realised after leaving my earlier post that my bus does of course have a tach (Doh!), because I look at it all the time to make sure I keep the engine in the green zone on the tach dial (it's has green, yellow and red, green being 'economy mode'). It's just that I've never looked at the tach when changing gear, and don't know what RPMs I'm 'supposed' to be changing at anyway; do manufacturers actually publish recommended gear change points for each a particular engine/gearbox combination, or is it just personal experience?

My bus has a Bedford 500 Turbo engine; the 500 is 500 cubic inches. I've no idea what the power output is supposed to be, but you are about right on the gearing - the top of the 'green zone' is 2000rpm, which equates to just over 60mph, and is where the speed limiter (not governer) kicks in. Although as a private owner I am now legally entitled to remove the speed limter I haven't decided if I will of not - if I do I will inevitably use the extra speed and drink more fuel, but then overtaking would be an awful lot easier as 95% of trucks in the UK drive everywhere on their limiters at exactly 60mph.

Jeremy
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« Reply #30 on: July 09, 2007, 08:10:37 AM »

I strongly suspect that running it up to the speed limiter as you are shifting to higher gears would be the proper rpm.
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« Reply #31 on: July 09, 2007, 08:31:50 AM »

Jeremy- I took a bus trip in Europe a few years ago and the bus was a DAF with a 12 liter engine in it (12 meter bus).  It had a 8 speed fully syncroed  trans in one gear shift.  The driver always (except on a steep hill) started in 2nd, skipped to 4th, then up the gears where at 100 km/hr he was cruising at a nice 1500 rpm.  For max fuel economy-on the flat notice where you can shift and have the engine come down to around 1200 rpm.  But for pulling a grade, just rev to the governor and shift.  Personally, I would slowly rev the engine until the governor hit, just to make sure it works.  My guess that will be around 2500 rpm.  500 cubes is not a very big engine (8.2 liters).  Is your engine a V-8 or 6 cylinder?  If it is a V-8 it might be the Detroit fuel pincher from years back since Bedford and GM are in bed together.  If it is a 6 cylinder, then it's probably a Bedford-which are good engines.  Don't be afraid to rev the engine.  You're not going to hurt it-they always set the governor way below max rpm for the engine-especially the Brits-being as conservative as they are with engines.  It can be as bad to run the engine to slow as running against the governor all the time.  Besides, you'll probably never put enough miles on the engine to get it close to being worn out. 
Like your bus size!  I have a 40ft'r, but next time I would like to use a 35ft x 102"-as long as the floor goes all the way to the rear of the bus with no engine or radiator intrusion-then I can just about use the same floor plan as I got now with my 40 footer's 3ft intrusion to the rear with the engine (transit bus).  Good Luck, TomC
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« Reply #32 on: July 09, 2007, 09:03:39 AM »

Jeremy- I took a bus trip in Europe a few years ago and the bus was a DAF with a 12 liter engine in it (12 meter bus).  It had a 8 speed fully syncroed  trans in one gear shift.  The driver always (except on a steep hill) started in 2nd, skipped to 4th, then up the gears where at 100 km/hr he was cruising at a nice 1500 rpm.  For max fuel economy-on the flat notice where you can shift and have the engine come down to around 1200 rpm.  But for pulling a grade, just rev to the governor and shift.  Personally, I would slowly rev the engine until the governor hit, just to make sure it works.  My guess that will be around 2500 rpm.  500 cubes is not a very big engine (8.2 liters).  Is your engine a V-8 or 6 cylinder?  If it is a V-8 it might be the Detroit fuel pincher from years back since Bedford and GM are in bed together.  If it is a 6 cylinder, then it's probably a Bedford-which are good engines.  Don't be afraid to rev the engine.  You're not going to hurt it-they always set the governor way below max rpm for the engine-especially the Brits-being as conservative as they are with engines.  It can be as bad to run the engine to slow as running against the governor all the time.  Besides, you'll probably never put enough miles on the engine to get it close to being worn out. 
Like your bus size!  I have a 40ft'r, but next time I would like to use a 35ft x 102"-as long as the floor goes all the way to the rear of the bus with no engine or radiator intrusion-then I can just about use the same floor plan as I got now with my 40 footer's 3ft intrusion to the rear with the engine (transit bus).  Good Luck, TomC

Hi TomC

Thanks for the reply - some useful information there which sounds about right for my engine, though mine is perhaps geared a bit lower than that. As you say, my engine is on the small side, although they still used the same engine in the full size 56-seat versions of the Paramount (mine was only a 35-seater). My Bedford is the only bus I have ever driven so it's hard to make comparisions, but I would say the power of mine isn't much more than 'adequate', and the capacity is certainly smaller than other equivalent buses, though it does have the turbo.

To answer your question, it's a straight six - Bedford's own design as far as I know. Apparently there are 'low' and 'high' pressure turbo versions of it, but I've no idea which mine is - as you say, I suspect both are fairly de-tuned anyway. The military are very big users of Bedford 500s in their 4x4 trucks, so I guess it is regarded as being basic and dependable, which suits me fine.

I originally got quite close to buying a Volvo B10M coach (very common over here), which have a 12.1 litre engine, but was steered toward the Bedford by a couple of people who said that although the Volvos (and I guess their equivalents) make great long-distances coaches, the Bedford engine would be better suited to a motorhome, being simpler and cheaper to repair and maintain, and using a lot less fuel.

The engine in my bus is mid-mounted, so the floor is flat all the way to the rear as you describe. You do of course lose some bagge bay space at the front with the mid-engine, but then you get a very large boot (trunk) at the rear to replace it.

Jeremy
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« Reply #33 on: July 09, 2007, 09:10:51 AM »

I strongly suspect that running it up to the speed limiter as you are shifting to higher gears would be the proper rpm.
Richard

Richard

The speed limiter I was describing is an electrical device that locks the throttle cable when a pre-set road speed is acheived - it doesn't actually control the engine RPMs in the same way that a mechanical governer does.

There is a sticker on the driver's window on my bus that records the yearly testing of the speed limiter as part of the annual safety inspection of the bus - just like the tachograph which measures drivers' hours, the speed limiter is a legal thing rather than something done by the manufacturer.

Jeremy
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« Reply #34 on: July 09, 2007, 09:37:35 AM »

When I drive this bus, I usually grind gears during downshifts

David
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David
When you downshift,between the first time you push down the clutch pedal and the second time.
Put your right foot right to the floor and keep it there.
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« Reply #35 on: July 09, 2007, 06:33:08 PM »

"Put your right foot right to the floor and keep it there."

only works (and does work perfectly) if you begin the downshift at a speed just a little higher than the limited speed of the lower gear.
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« Reply #36 on: July 09, 2007, 07:30:21 PM »

Drat and darn....

we need some video to link to.

trying to describe downshifting in words does not work.

My coach is automatic, showing a 10 speed tractor trailer downshift doesn't help...

happy coaching!
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« Reply #37 on: July 09, 2007, 09:40:52 PM »

Jeremy, I think that your concern about revving your engine up to governed speed is misplaced. EVERY diesel has a governor; they are necessary becouse of the way that fuel injectors work.

The governed speed is not the danger mark; it is the upper end of the normal working range.

I have some of the same biases that you do; when I don't have to get the maximum power, I shift before I reach governed speed, too. My reasons may be a little different than yours.

I know that injectors increase their output as their stroke rate rises. But, looking at the torque curve, I see that torque rises with RPM and then falls off. Since I know that fuel is increasing, I reasoned that fuel economy must be a little better while torque is rising than when it levels off or falls.

When possible, I try to operate the engine at the best mix of RPM and torque that is still safe for the engine. In our standard timed two stroke, that seems to be between 1100 and 1600 for light loads and 1500 to 1950 for hard uphill pulling.

It may interest you to know that many transits are run right against the governor when they get on the freeways, because they are geared so low. With one more gear, their economy improves quite a bit.

For what it's worth.

Tom Caffrey
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« Reply #38 on: July 10, 2007, 07:26:22 AM »

I suspect there is quite a difference in shifting than in normal operation, especially as regards mpg.

The relative short time that an engine would be at the governed rpm during shifting as compared to the time that the coach is driving down the road at the most economical rpm would generally be insignificant. Just run it up to governed speed, shift and quit worrying about lt. LOL
Richard
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