M51 Clutch adjustment

[M51clueless]

M51 Clutch issues,

I can’t get the clutch to disengage when depressing the clutch pedal.
First noticed a change in the friction point the other day, the pedal was much closer to the floor (full travel) before the clutch would disengage.
I attempted to adjust the linkage and thought it was some better.
used the truck for about an hour and the clutch got progressively worse, to the point that the clutch will not disengage now.

I have checked the linkage again and detect no issues.
I have looked thru the TM’s and have not found any thing useful.

Hoping you know what the fix is and that it doesn’t involve dropping the transmission.

Thanks for any ideas

 

[NDT]

Time to pull up the transmission cover and open the inspection cover and see what’s going on in there. Sounds like the pressure plate is shot.

 

[M51clueless]

I had pulled the inspection plate , looked in it but couldn’t tell much.

Up till now the clutch had been flawless, smooth when engaging, does not slip.

My understanding is the linkage presses against the throwout bearing, separating the clutch from the flywheel overcoming the springs in the pressure plate.

 

[M51clueless]

When I look thru the inspection hole what am I looking for?

Not seeing much except the edge of the clutch and pressure plate l think.
Also I have noticed the clutch is easier to press, and when depressed I can hear a little bearing noise, guessing some pressure is being applied to the pressure plate.

 

[US6x4]

May not relate exactly to a medium/heavy duty setup but those same symptoms happened to my '75 Ford F-250 when 1 of the 3 fingers on the pressure plate that the throw out bearing engages broke off.

 

[simp5782]

Symptoms point to a bad pressure plate.

 

[M51clueless]

I was afraid you guys were going to say that, Guess I’ll be spending the next few days under the truck.

Thanks for the advice, just wanted to be sure before I started dropping the transmission.

 

[simp5782]

You can use all thread in a few of the bolt holes, remove shifter and driveshaft and slide the transmission back just support it with the jack so it's a quicker job than having to wrestle it back up

I've done a few in the field with just a ratchet strap to support it.

 

[M51clueless]

You can use all thread in a few of the bolt holes, remove shifter and driveshaft and slide the transmission back just support it with the jack so it's a quicker job than having to wrestle it back up

I've done a few in the field with just a ratchet strap to support it.

simp,
I think you were the guy that posted the parts list I found last night , didn’t see any m51 multi fuel parts, do you know a parts number for the clutch assembly?

 

[simp5782]

simp,
I think you were the guy that posted the parts list I found last night , didn’t see any m51 multi fuel parts, do you know a parts number for the clutch assembly?

You could have it rebuilt if you have a shop near you

Or @SecoParts has them in kits or Ed at Memphis equipment can help you.

Where in TN are you located?

Pressure Plate Is NSN 2520000974152

Or a simple ebay search for m54a2 etc would find some stuff.

 

[GopherHill]

The clutch disk may have shed the lining and wedded up. I've seen that happen. Best pull the clutch and replace parts. Don't forget the pilot bearing.

 

[M51clueless]

Thanks for the input, got a clutch assembly coming from Memphis Equipment,
simp , I am on a farm outside Bell Buckle, close to Murfreesboro

 

[BEASTMASTER]

did my buddies once , roll the windows down and put a 6x6 on the doors, or use a good piece of pipe or what ever, a small chainfall or a come a long makes life easier. my 2 cents ?

 

[M51clueless]

Thanks for the tip, clutch already showed up, out of excuses going to start on it today

 

[M51clueless]

Just wanted to update the thread,

Was able to do the clutch job yesterday,
Removing the drive shafts shifter, clutch linkage, pto shaft, all went smooth.

Getting the bolts out of the transmission, easy enough.

Spent some time rigging ratchet straps ( used several) to support the transmission. Once I took out the last 2 bolts it slid right out.

Got my replacement clutch from Memphis Equipment, had the add a clutch alignment tool. Don’t know how you could do the job with out one.

Guess when I was sliding the transmission back it was at enough of an angle that it popped the carrier bearing out of the flywheel, that was a bit of luck.

Removing the old pressure plate and clutch was easy
My release/throw out bearing had seized, and the pressure plate fingers were shot.

Installing the new clutch and pressure plate went smooth too, I had left the transmission hanging down a foot or so and back as far as I could get it. That did limit working room but well worth not dropping the transmission all the way out. I had rigged my straps over the top of the truck, I do have a hard top, that helped to be able to leave the doors open. That way I was able to work from inside the cab too.

Now the fun part, nothing like trying to precisely align 800lbs of transmission and not be able to see the hole the shaft has to go in.
I had watched a youtube , a guy had done on a non-military truck. He kept measuring top, bottom and sides to help with the alignment of the transmission to the bell housing

I spent an hour but she finally gave in, that happened in 2 stages, transmission shaft finally going thru the clutch, then a little more wiggling to get the shaft to slide into the carrier bearing. I had put a little grease on the transmission shaft, I think that helped.

Rest was a piece of cake.

Thanks for all the good advice.

 

[Ajax MD]

@M51clueless Excellent, thanks for the write-up. I own an M813 with the same setup (more or less) and your lesson will help me if I find myself needing to do this. I do have the luxury of a 1-ton commercial truck transmission jack.

 

[Recovry4x4]

Glad you got it in there. They can sometimes be quite finicky. Fun story, a great number of years ago a group did an M35 engine swap at the GA rally. Those poor souls fought with getting that trans slid in for a good long time. As they were getting more frustrated, I asked if I could give it a shot. They relented and I slid in place in just a few minutes. From up close it looked like it was aligned perfectly. From 5 feet away you could see the mis-alignment. I was just a fresh pair of eyes.