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Author Topic: Clutch and adjustment data for MC9, please.....  (Read 2186 times)

« on: June 19, 2006, 05:14:41 AM »

There is such a thing as beating a dead horse and I'm not one to normally do such a thing but....

After a night of tossing and turning I made a call early this morning to the man who's working on my MC5.  The original 15" twin disk clutch (and flywheel) had been replaced with a 17" single disk unit and was slipping.  He's pulled the engine and recommended that we reman the 17" and go with it.  Since it had given me problems I questioned the logic in changing from what the Engineers had designed for that bus and he reassured me that it would be OK.

In talking with him this morning he told me that he'd had a MC9 over the pit on Friday and was curious about that clutch so he removed the inspection plate and found that the '9 too had a 17" single disk clutch.  My concern in staying with the 17 was that there was no established criterea for the proper maintainence and adjustment of the 17" in a 5.  However, if because the 15" Twin is no longer available and the 17" (from a '9?) was retrofitted then would it not follow that the adjustment procedure for the '9 would then apply to my unit?

We don't know if there is much difference in the linkage setup and that is primarily the reason for my once again broaching this topic, with apologies for being a PIA about it.  But there's just too much money involved here to make the same mistake twice!

If any of you MC8 or 9 owners have a manual which would cover the adjustment procedure of the clutch for a standard transmission
(and a 17" Clutch) would you kindly share that information with me?  Perhaps that way we can bury this horse for good and always.

I apologize for the redundant offerings on this subject and will refrain from being a PIA about this or any other topic in the future.

Thanks for your patience.

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« Reply #1 on: June 19, 2006, 07:42:10 AM »

One of the reasons that the clutch was probably changed to the 17" single plate is that the 15 1/2" twin plate tends to be grabby since they are usually ceramic lining compared to the 17's organic type.  While the 17" will be smoother (say more comfortable for the passengers) the 15 1/2 will usually last longer.
As to clutch adjustment, I know that the 15 1/2" clutches in trucks have clutch brakes that activate when you push the clutch pedal all the way down to the floor and continue to push moderately hard on the floor (used to brake the spinning gears and clutch so to be able to initially get the transmission into gear without grinding the gears).  Whether the 17" has it, I don't know.  Any clutch adjustment is the same.  You need about an inch of free play at the top of the clutch pedal so you are not exerting pressure on the throw out bearing. Second, when you push the pedal down to the floor, the gears should stop rotating and not drag. With soft pressure on the gear shift lever and the clutch pedal all the way down, if you start getting some gear grinding from the clutch starting to engage about 2 inches above the floor, it is adjusted right.  If there is a clutch brake also, there is a specific method of adjusting it.  Usually you adjust the clutch first for proper operation, then readjust the brake for bottom of clutch pedal operation.
Personally-I'd switch back to the 15 1/2" clutch since that is the standard of the industry for trucks, and they have many different styles to choose from including the Eaton Solo clutch that is self adjusting and has the Easy Pedal option (to save your left leg in traffic)  Good Luck, TomC

Tom & Donna Christman. '77 AMGeneral 10240B; 8V-71TATAIC V730.

« Reply #2 on: June 19, 2006, 09:51:29 AM »

Thank you for your answer Tom, and I don't wish to sound contentious in view of the effort you went to in asnwering my question.
The trucks using the 15" Double disk clutch are "pull to release" and the bus operation is like automotive, it's  "push to release".
That's primarily the reason I'm having such a devil of a time finding a replacement clutch for my bus.  The flywheel has been changed to accomodate the 17" clutch and the linkage is "push to release".  Any rebuilder who might have to old double disk clutch parts is reluctant to build one and lose the core...too it means a flywheel change, if I could find one.

I'd have been in favor of doing just that...to keep with what the design Engineers had in mind when they drew up the plans for the 5.
But, that isn't in the cards I've been dealt.  I've been through this with many members of this board and the experts up to and including RJ Long.  There isn't a concrete answer out there...unless I go to Engineering at MCI and you can imagine what that's going to be like.
If it isn't a current model or less than 10 years old...they don't want to know about it.

Hopefully someone who is running an 8 or a 9 will take the time to look up the info I need in both their Parts and Service manuals and advise me. In the meanwhile we're in a holding pattern on this matter.

Thanks again, Tom.  We'll cross our finger and hope.

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