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Author Topic: Driving in 3rd gear?  (Read 4360 times)
5B Steve
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« on: February 11, 2011, 06:46:02 AM »


   I was just wondering, if and when one was in heavy traffic and you had to downshift to 3rd and had to stay in that gear, how

   long could you go.   It's sounds stupid to ask but I was curious.
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smokedetector
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« Reply #1 on: February 11, 2011, 06:48:48 AM »

Until you run out of fuel?
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Jon Morgan
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« Reply #2 on: February 11, 2011, 07:03:51 AM »

Aside from the fact that third gear is less efficient than fourth (two additional gear power transfers compared to direct drive in fourth) there's no reason in the world not to run in third gear for as long as you like, presuming it's a manual box.  Automatics I don't know about.

Brian
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Oonrahnjay
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« Reply #3 on: February 11, 2011, 07:29:39 AM »

If it's the right gear to match your speed (whether dictated by traffic, terrain or other conditions) and the right engine RPM, it's the right gear.  Stay in it until things change and you need to shift to 2nd or 4th.
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5B Steve
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« Reply #4 on: February 11, 2011, 07:58:28 AM »




    Brian, thanks for the response, just like yours it its a 4 speed.

    Steve 5B....
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5B Steve
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« Reply #5 on: February 11, 2011, 08:05:31 AM »

 

  Oonrahnjay, thanks that makes sense for I have been in heavy traffic and keep shifting between 3-4 back to 3rd and so forth.

  I just didn't know how long you could go!


   Steve 5B....
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TomC
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« Reply #6 on: February 11, 2011, 08:09:51 AM »

With only 4 speeds, the idea was to rev to the governor and shift.  That's also why the speedo was color coded so not to have you lug the engine down to far.  While you're in the range of 3rd gear, there really isn't anyway you can shift to another gear.  When you get up towards the governor, then shift into 4th.  If the engine accelerates in 4th, then that's the gear you should be in.  Over revving the engine (anything over 1800rpm) is just burning additional fuel and exerting extra wear on the engine.  For the most accurate engine speed analysis, you should have a tachometer.  When I installed my tachometer, with my Allison V730, I was quite startled that you could get 2nd gear lockup as low as around 20mph with the engine dropping down to 1100rpm (on a very light pedal)!  Good Luck, TomC
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« Reply #7 on: February 11, 2011, 03:32:23 PM »

I've run my 4104 four speed 7-10 miles on long grades in third and even second part of the time. The engine doesn't care what gear you use as long as you don't lug it. Two strokes don't mind high rpms in fact they like it. They really sound nice too!!

If you lug it in hot weather it will get hot, if you are in a lower gear and not lugging it will stay cool forever if you're moving along.

I've also gone miles in 2-3 in construction zones, no problems at all and no reason for any problems.
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PD4107-152
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Barn Owl
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« Reply #8 on: February 11, 2011, 03:35:53 PM »

I can run my V730 all day in third gear without any problems!  Grin
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L. Christley - W3EYE Amateur Extra
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« Reply #9 on: February 11, 2011, 04:52:16 PM »

Steve 5B -

Not contradicting, just offering my 2 cents. Besides, I've got a 5C so figured my experience might be relevant.

When I hit a city limit or construction zone, 3rd is my gear of choice. Has a decent power / speed range - I can keep the revs up or, if need be, just crawl along.  Sometimes I just leave it there, especially at night in hilly terrain (never know what's up ahead). Or just because I'm pure a** lazy...  Cheesy

I might (on second thought) offer one mild (and by no means expert) contradiction:

I know Tom's right about the procedure ("... rev to the governor and shift...") but I seldom do it. I like to shift (up or down) when it's comfortable, usually 'up' around 1600-1700 and 'down' before lugging. I seldom need to double-clutch (unless I screw up  Embarrassed) and the bus seems quite happy this way (but you may be geared differently).

I just love my '5', don't you?  Wink

 Nellie
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Ed Hackenbruch
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« Reply #10 on: February 12, 2011, 06:36:02 AM »

I have run my automatic a loooooooooong way in third before.  A 55 mph speed limit is tough for me, in third i will be running about 21 hundred rpm and i lose about 20% mpg.  My shift point into 4th is about 57 mph but to keep from lugging it i need to be running at least 63 to 65 mph so that my rpms will be 1700-1750.
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« Reply #11 on: February 12, 2011, 08:03:36 PM »

My V730 will not run in 4th under 50mph so that gives me no choice, however, I love it!!
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PD4107-152
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« Reply #12 on: February 12, 2011, 11:07:21 PM »

Ed, what rear gear do you run?

My MC8 with 8V71N, HT740 and 3.7 differential will run at an indicated 50 mph in 4th and accelerate if the land is relatively flat, so no lugging.

If the speed drops much below there with the accelerator pedal depressed, the Allison takes care of business if I don't, by downshifting to 3rd. Somewhere 46/47 mph indicated, so I shift it down myself smoothly with a lift throttle and push forward the shifter ahead of that speed if acceleration is needed.

45 mph speed limits are the devil for my set-up, pretty much right at the minimum shift point.

happy coaching!
buswarrior
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« Reply #13 on: February 13, 2011, 05:33:47 AM »

I think the definition of "lugging" is lacking.  I see no particular harm at running the engine at lower rpm if little power is required, like cruising along at a steady speed on flat ground.  If you need to accelerate, you can always downshift.  But if the engine makes maximum torque between 1200 and 1600 rpm, I just don't see where running it at those speeds can be all that harmful.  The governor based shift points are based on maximum acceleration.

or am I totally out to lunch?  I do cruise along at 45 - 50 in fourth all the time.  Roads around here, with an 80 kmh speed limit, almost demand that.

Brian
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Ed Hackenbruch
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« Reply #14 on: February 13, 2011, 06:06:05 AM »

BW, 3.36  and i usually manually downshift my 644 a couple hundred rpm above what it will do on its own, so as to keep my rpm up so i don't start heating up.  Brian, the PO had to rebuild my 8v71 once because he was not paying attention and was "lugging" it for too long.  For optimal cooling on my 5A it needs to run at about 1700 rpm so that the squirrel cages are drawing enough air thru the radiators.  There are a lot of times where i am running at lower rpm but when i do that i keep a very close eye on the temp gauge and if it starts to climb i will downshift to get my rpm back up. I usually run right at 175-180 degrees.
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1968 MCI 5A with 8V71 and Allison MT644 transmission.  Western USA
buswarrior
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« Reply #15 on: February 13, 2011, 08:26:24 AM »

roughly speaking, with a 3.36, 50 mph is 1400 rpm in 4th, and 55 mph is 2100 in 3rd/1500 rpm in 4th.

with a 3.7, 46 mph is 1400 rpm in 4th, and 50 mph is 2100 in 3rd/1530 rpm in 4th.

Most Allisons are thinking hard about downshifting around 1400 rpm.

Ed, how are your seals around the rads? Rads in good shape? Engine hot-rodded without a cooling upgrade?

Your strategy is exactly the right one to compensate for a cooling problem, get the fans spinning, and the water pump pumping by keeping the rpm's high.

You might have a simple fix?

On mine, I left the ratty rubber seals around the new rads in place to act as a form, and spray foamed all the way around. Easy to dig it out the next time. You want absolutely NO air sneaking past, you want it all going through the rads. Also, check the door seals on the fan compartment. I continue to tape mine to seal them from the outside until  I work out a better style of seal from available bits and pieces. The old ones are hard, and the door doesn't faithfully fit against them anymore. Coloured duct tape to match the paint looks ok.

Most "lugging" problems stem from a lazy (or uninformed) driver not downshifting a manual transmission when they should, and let it drag down and down, typically, the top of the hill is approaching...trying to save the shift down and the shift back up again. 2 stroke Detroits heat up very badly by doing this. Piston temps, they say, get to destruction temps.

A properly operating automatic really won't let you easily "lug" the engine.
Speed drops off, and then it downshifts, whether we like it or not!

happy coaching!
buswarrior

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Ed Hackenbruch
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« Reply #16 on: February 13, 2011, 04:19:42 PM »

Seals are in pretty good shape, never had reason yet to pull the radiators out, engine not hot rodded, has the n60 injectors, no turbo.  My allison wants to downshift at about 1440 to 1450 rpm.  Smiley
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« Reply #17 on: February 13, 2011, 04:30:40 PM »

Brian,

I agree, I've run the 4104 many miles in 4th on flat ground or slight downgrades at very low speeds, that is not lugging, that is almost coasting.
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PD4107-152
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« Reply #18 on: February 14, 2011, 07:03:03 AM »

BW why does it matter what the driver is wearing?
Grin  BK  Grin
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Busted Knuckle aka Bryce Gaston
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« Reply #19 on: February 14, 2011, 07:14:55 AM »

yup, I knew someone would...

roflmao!  Grin

happy coaching!
buswarrior
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Nellie Wilson
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« Reply #20 on: February 15, 2011, 03:00:40 AM »




BW why does it matter what the driver is wearing?
Grin  BK  Grin

Huh?

yup, I knew someone would...

roflmao!  Grin

happy coaching!
buswarrior


Huh?

I get the 'lmao' part, but what's the 'rof' part mean?

Nellie
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« Reply #21 on: February 15, 2011, 03:42:03 AM »

guessing its read as un-uniformed bus driver.   rof =rolling on floor.
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« Reply #22 on: February 15, 2011, 07:54:18 AM »

Please, please, take me in and feed me.

happy coaching!
buswarrior
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RJ
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« Reply #23 on: February 15, 2011, 10:20:24 PM »

Nellie -

Since my French is SO bad, let me try and translate BW & BK's exchange from English into American for you:

#1:  BW said "Most "lugging" problems stem from a lazy (or uninformed) driver not downshifting a manual transmission when they should. . ."  What he meant was a non-educated driver, not one who was out of uniform.


#2:  BK then asked "BW, why does it matter what the driver is wearing?"  Here BK is making a (bad) pun or joke out of the single letter difference between un-in-form-ed (not educated) and u-ni-form (clothing).


#3:  BW's response "yup, I knew someone would..." is simply acknowledging that BK put together a bad pun using BW's own words.


As for BW's last response about needing to be fed, you, of all people, should understand how fellow countryman BW is suffering.  After all, he's stuck with Big Transit during this time of year while you've fled to FL.

The men in the white coats will be along soon to assist in easing BW's suffering!


Next time you run across an Internet Acronym that you don't understand (roflmao or obama), you can look it up here:

http://www.gaarde.org/acronyms/

Oh, wait, obama is not on the list - yet.

FWIW & HTH. . .  (For What It's Worth & Hope This Helps)

 Wink
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RJ Long
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« Reply #24 on: February 16, 2011, 03:50:01 AM »

My Dear RJ -

You saved me from a long sleepless night. Maybe if I read enough I'll develop some 'board intuition,' but right now lots of things fly right over my head.

Same to you, DMoe (gee, why couldn't I figure all that out?)

(RJ - Better watch that political talk... got some pretty scratchy viewers out there) Grin Wink Smiley

Quote
Please, please, take me in and feed me.

Really? C'mon over, BW... you'll like the weather.

Nellie

Oooppps! Guess the sleepless night already happened. Oh well, I like morning snoozes. Smiley

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« Reply #25 on: February 16, 2011, 08:36:10 AM »

Brian, since I too have the 4 speed in a 5A I feel somewhat qualified to put my 2 cents in with the rest. My personal parameters are stay in third in traffic and not concern myself unless traffic starts to move along at a consistant 55 MPH, That holds my engine RPM's at about 1800 and allows my Jake's to still be somewhat effective (should I have them switched on) and need them. I have no compunctions of keeping in 3rd at 55 for prolonged periods as I'm maintaining no more engine revs than I am at 65-70 in 4th.

I'd rather have the help in fast braking, if necessary, from both the engine falling revs and the Jake's than have to make a panic stop with brakes alone.

FWIW

NCbob
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« Reply #26 on: February 16, 2011, 08:37:30 AM »

Sorry Steve, guess my noodle isn't on straight today.

NCbob
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« Reply #27 on: February 16, 2011, 08:58:53 AM »

NCBob, you must have lower gearing than I do.  I have a 3.7 diff, and with 495 rev/mile tires I tend to be on the governor around 2150 rpm at 70 mph, and at around  53 mph in third gear.  I run 45 - 50 mph in fourth all the time, that's 1375 rpm to 1525 rpm (if my calculator and my mind are both working right, which is always a question) and shift down to third if I can't accelerate in that gear/speed, and of course if I run along into an uphill grade or want my jake brakes to actually do something useful...  As noted, that's kind of coasting along.  Light throttle, temps stable at 180, listening to country music on the radio... Smiley

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1980 MCI MC-5C, 8V-71T from a M-110 self propelled howitzer
Spicer 8844 4 speed Zen meditation device
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Len Silva
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« Reply #28 on: February 16, 2011, 10:05:58 AM »


Next time you run across an Internet Acronym that you don't understand (roflmao or obama), you can look it up here:

http://www.gaarde.org/acronyms/

Oh, wait, obama is not on the list - yet.

FWIW & HTH. . .  (For What It's Worth & Hope This Helps)

 Wink


OBAMA  Our Blessed America Moves Ahead
    or
Our Best Alternative Miraculously Appears
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« Reply #29 on: February 16, 2011, 10:24:52 AM »

For the other side of the house, and only to amuse myself...

OBAMA - Oh bother, a militant arab

for Nellie - Oh boy, a musical apparition!*

for our Jewish friends (specifically a guy named Mike Rosen who used to go Yiddish on me from time to time, and in no way intended as a jibe at President Obama, a man whom I have deepest respect for...)

Oy, bupkes, another meshugener already!

my contribution to thread drift for the day...

* Apparition can be defined, if you follow the lexicography a bit, as a "phantom of loveliness", so appropriate for our Nellie, who sometimes disappears...

Brian
« Last Edit: February 17, 2011, 05:11:04 AM by bevans6 » Logged

1980 MCI MC-5C, 8V-71T from a M-110 self propelled howitzer
Spicer 8844 4 speed Zen meditation device
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1972 NTM MK-4 B/SR
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« Reply #30 on: February 16, 2011, 01:51:46 PM »

Well guys, here you go again.

You really need to get over that anti-Obama stuff and stick to buses!!

It is tacky!!
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buswarrior
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« Reply #31 on: February 16, 2011, 07:12:16 PM »

ROFLMAO!!!

Brian is a comedian:

* Apparition can be defined, if you follow the lexicography a bit, as a "phantom of loveliness", so appropriate for our Nellie, who sometimes disappears...

Never mind Waldo, where's Nellie?

happy coaching!
buswarrior
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Nellie Wilson
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« Reply #32 on: February 16, 2011, 10:57:18 PM »

 Smiley *Sigh* Smiley

Thanks for a much needed lift, Brian and BW...

Luv ya,

Nellie
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