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Author Topic: Shifting without a clutch question.  (Read 3876 times)
TomC
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« Reply #15 on: November 19, 2010, 07:35:25 AM »

Bevans6-that Spicer looks very different from a Roadranger transmission.  That Spicer looks more like a large car transmission with regular synchronizers.  The Roadranger has a square shaped slider without synchronizers that is made to lightly "grind" into gear everytime (as demonstrated by my 850,000mi trans life).  On a transmission with synchronizers you should NEVER not use the clutch-in other words-ALWAYS use the clutch on a synchronized transmission since not using the clutch will quickly wear out the cone clutches of the synchronizers.  Good Luck, TomC
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Tom & Donna Christman. '77 AMGeneral 10240B; 8V-71TATAIC V730.
bevans6
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« Reply #16 on: November 19, 2010, 07:52:04 AM »

Hi Tom, that was my thought as well.  Aside from not having synchromesh cones the sliding hubs on this 4 speed Spicer are a lot like a normal automotive gearbox, just really big.  It's definitively not a synchromesh box, as those of us who have them know very well...  But the point that truck transmissions have very different sliders that are designed to engage easily without the clutch is well made.

I think this is why I have found learning to shift the Spicer by far the hardest thing I've done so far, driving-wise.  Absolutely the hardest thing to shift I have ever encountered, including a number of other non-synchromesh boxes.

Brian
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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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1978 Lola T440 Formula Ford
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Fred Mc
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« Reply #17 on: November 19, 2010, 08:51:56 AM »

Although I don't drive my bus an awful lot, I really have no trouble shifting up or down, double clutching or not. When I first drive it after a long layoff I grind a little but soon get smooth shifts.
However, I decided to try shifting without the clutch and didn't have too much problem with that either. BUT on a couple of occasions the shift was very hard judging from the heavy "clunk" I heard. I decided at that point the tranny probably wasn't meant to be used that way and that catastophic results could occur should everything not mesh properly. So I quit doing it. I just resigned myself to the fact that I wasn't driving a race car anymore and taking my time shifting made it much smoother and easier.

It amazes me that we buy these old buses with a zillion miles on them and then go through all the effort to "baby" them like it was a brand new $300000 Ferrari. And then we do things to them that they were never designed to do , like clutchless shifting. Puzzling!
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kyle4501
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« Reply #18 on: November 19, 2010, 11:39:54 AM »

The only thing a synchromesh cone does is to speed up or slow down the input side of the transmission to match the output side. If you don't have those cones (or something like them), then it is up to the driver to do it. Usually it is easiest by using the clutch & throttle.

I still maintain that if your shifts are smooth & silent, you aren't hurting anything - regardless of clutch use.

It is possible to damage the transmission during shifting even if you are using the clutch.
It is quite easy to KNOW if you are causing damage - grinding noises, shifter vibrating as it goes in gear, lurching, etc are all indicators of damage occurring.

My vote is to use what ever method that works for you to enable the smoothest shifts possible.
Smart people with limited funds will, of course, start with the most common method - & that will involve double clutching. . .

BTW, as I understand it, the double clutching event is:
Clutch in - unloads drive train to allow you to slide it out of gear without any load on the gears.
Clutch out - allows you to use the engine to speed up or slow down the speed of the input gear to match the speed of the output gear. (takes the place of the synchromesh cones) 
Clutch in - allows you to slide into the desired gear without any load on the gears.
clutch out - allows the engine to supply power to the rear wheels.
 
Bottom line is the gears have to be at the same speed to engage - it is up to the driver to get them there . . . .Unless you have some form of an autoshift.  Grin  Cool
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I know you believe you understand what you think I said, but I am not sure you realize that what you heard is not what I meant. (R.M. Nixon)
RJ
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« Reply #19 on: November 19, 2010, 11:45:10 AM »

Greetings, all, from Spangdahlem!

Since I wrote the article over on BNO about shifting, I'll throw in a couple of comments here. . .

I still recommend using the clutch to shift, double-clutching those with non-synchromesh transmissions.

I sometimes cheat and up shift w/o the clutch, but rarely.

Sometimes I hybrid up shift - clutchless to take it out of gear, clutch in to grab the next one -very easy to do w/ a GMC/Detroit.  Gotta "feel" it!

I ALWAYS double-clutch downshifts - too much mass spinning around back there to screw up.

What's always amusing to me is teaching newbies how to downshift as they're pulling a grade while keeping the throttle floored the whole time!  You should see the looks ("WTF??")  LOL

FWIW & HTH. . .

 Wink
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RJ Long
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Lee Bradley
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« Reply #20 on: November 19, 2010, 03:02:43 PM »

Contrary to intuition; most damage occurs to the drive train using the clutch.  When you shift without the clutch, you must have the rpm matched between the engine and the drive train or the gear coupler will not engage and no undo loading of the drive train can occur. With the clutch released you can select any number of wrong gears or even if you select the correct gear, the rpm delta between engine and drive train changes at an amazing rate, so if you are just a little late getting the clutch released those huge torque loads are applied to the drive train; broken axles, twisted drivelines, shatter u-joints, even broken crankshafts. Those loads almost impossible when not using the clutch. My experience was mostly in a KW with a 262 hp Cummins with a 5 and 4 with 300 rpm between gears.  You have no idea how fast the road speed drops while chasing gears on some of our Pacific NW hills with 80,000 pounds.
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gus
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« Reply #21 on: November 19, 2010, 05:55:31 PM »

Obviously you can't clutchless shift with a load on the gears, most people should be able to understand that? I don't know that any manual gearbox can be shifted while loaded, clutch or no?

All you have to do to unload the gears is take your foot off the go pedal - simple. If you aren't already pushing it, push and then release. Same results.

All this talk about locked up drive lines and damaged gears is a complete mystery to me? I've never once seen this situation in over 60 yrs of driving, maybe I will someday.

I never said I don't crunch gears, I do it regularly on the 4104 - but there is no difference in crunches between clutch or no clutch shifting for me!! I don't think anyone can drive a 4sp Spicer in a bus and never crunch a gear!!!

I have a bunch of older vehicles from a Jeep to a 10 sp Dodge C900 truck tractor and I shift all them without using the clutch. Not all the time, it depends on the situation, but most of the time.

I'm still waiting to have my first damaged transmission.
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Tony LEE
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« Reply #22 on: November 19, 2010, 11:01:36 PM »

When I changed the 13 spd transmission to the Allison HT740 in my truck, the PO had to overhaul the transmission at 350,000mi.  I changed it at almost 1.2 million.  So I got 850,000mi out of my transmission and the clutch was original.  My suggestion is to upshift without the clutch but use the clutch for down shifting-that's what I did and obviously it worked.  Good Luck, TomC
But Tom,   you've got skills!   Grin  Grin  Grin

And he has 1/4 of the spacing between gears than we have in the bus. I imagine that helps just a tad.
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TomC
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« Reply #23 on: November 20, 2010, 07:39:35 AM »

Especially when trying to pull a hill, using the clutch can speed up the shifting process.  Even with a non synchroed transmission, using the clutch on a hill you can pull the gear shift in faster by grinding it in forcibly.  Sometimes waiting for the engine to coast down to the next gear would bring you to a stop.  If you're really skilled, you can use the Jake brake to slow the engine faster to speed up shifts. Good Luck, TomC
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Tom & Donna Christman. '77 AMGeneral 10240B; 8V-71TATAIC V730.
RJ
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« Reply #24 on: November 20, 2010, 01:54:45 PM »

All -

However you decide to shift your manual/automatic transmission:

"Don't spill the red wine!!"

 Wink
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RJ Long
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Ed Hackenbruch
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« Reply #25 on: November 20, 2010, 07:06:11 PM »

Or the Pepsi    Wink
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1968 MCI 5A with 8V71 and Allison MT644 transmission.  Western USA
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