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Author Topic: Clutch Issue on a 1972 GMC P8M4108A  (Read 1491 times)
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« on: October 11, 2012, 08:26:44 PM »

Hello Friends,
I am new to this message board and I only recently bought a 72 GMC P8M4108A with an 8V71 Detroit Diesel and a 4 speed manual transmission with a wet clutch.  For the few months I have owned it, I have only taken it around the block several times, never on a road trip.  The bus ran fine going around the block and the transmission seemed to operate as it should, that is it was hard to get into first gear and the clutch pedal required a lot of leg.  According to what I read, this is normal. Well, about two weeks ago, I was going to take the bus out for a spin and while I was trying to get the gearshift to go into first gear, the clutch suddenly went to the floor and would not come up again unless I pulled it up with my hand.  The spring attached to the clutch pedal is still attached, and with the help of a friend I was able to determine that the linkage running from the pedal to the clutch lever on top of the clutch housing is still hooked up.  The problem is somewhere in the clutch housing.  I am able to move the lever on top of the clutch housing back and forth without resistance and this is the problem.  Can anybody tell me what happened?  Has anybody ever experienced this problem where the clutch pedal suddenly went to the floor?  Some people tell me the throw out bearing pulled through the fingers in the housing.  Some people tell me the fiber clutch probably disintegrated.  Another person told me that perhaps the bolts that keep the clutch fork straight might have sheered off or came loose.  I would appreciate any suggestions or ideas.  I have a mechanic friend that said he would help tear the clutch apart, but I would like to know what to look for before we get into it.   Also, where do I find parts when I find out what I need?  Thanks to everybody who read this.  I appreciate anybody who can give me any information.  Thanks again.  Corey   
Tony LEE
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« Reply #1 on: October 11, 2012, 09:28:08 PM »

Isn't there a large inspection cover on the bottom of the bell-housing that will give you a pretty good view at the clutch workings.

Also that lever is on a spline on the shaft and the clamp may have undone or the splines have stripped in the lever.

Not relevant to this issue, but does yours have any sort of clutch air-assist like the MCIs

Best do some careful inspection before "tearing the clutch apart" because first you have to get the clutch out on the ground and before that have to get the gearbox out and before that have to .....
« Last Edit: October 11, 2012, 09:31:57 PM by Tony LEE » Logged

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« Reply #2 on: October 11, 2012, 09:41:06 PM »

Luke Bonagura at U.S. Coach is an absolute expert on your coach.  Call him and he will diagnose it for you.  His number is elsewhere on this site.

'81 Eagle 15/45, NO MORE
'47 GM PD3751-438
'65 Crown Atomic, NO MORE
Vancouver, WA USA
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