Clutch slipping....

[refit1701]

Now that I have around 550 miles on my engine with new clutch, it is slipping enough on hills to be noticeable. I put a new, relined clutch plate on it and had to install 1/8th inch washers to allow the throwout bearing to reach the fingers on the pressure plate. Could it be that with only 500 miles on it (and two parades totaling 6 miles) that the clutch has worn enough that those washer need to come out?

This is on the heels of my having to adjust the clutch pedal so that the clutch would FULLY release and the transmission would stop spinning at a full stop.

What's going on here??

[Cal_Gary]

Hi John,
The washers are costing you some of your disc pressure so I'd recommend removing them. You shouldn't have lost much disc surface with so few miles; again I suspect the washers.
How much pedal free travel do you have? The TM calls for 1 inch.
Is the clutch fully releasing when you get off the pedal?
Do you have adequate travel from the bearing to engage the clutch fingers when the pedal is depressed? (This will take two guys to check). My 8030 manual offered nothing about the pressure plate, but my Ahl Resto Guide shows an exploded view of the pressure plate, and as I suspected, the clutch fingers appear to be adjustable. Do you have the clutch manual? It might include how to adjust those fingers. Unfortunately I do not have that manual so you'll need to follow up on that part.

As an FYI, I had screwy clutch issues until I went with a Power Wagon clutch rod from VPW. Provides greater adjustment flexibility because one end clevis is threaded.

Let us know what you find out-at least you won't have to drop the tranny to remove the washers.
Gary

[Cal_Gary]

Hi John,
Just checking in to see what you found out....
Thanks,
Gary

[refit1701]

Hey Gary...didn't get to do any work until late yesterday!

I first looked at adjusting the pedal but there's really more adjustment on it. So I removed the clutch cover and took out the spacers between the flywheel and pressure plate.

Now I am back where we were when we put them in; the throwout bearing doesn't reach the pressure plate fingers at all. I tried adjusting the pedal but there isn't enough adjustment to reach them. I am wondering if the linkage section with the double clevis is wrong. Here's a photo of it....the length from center hole to hole is 4.5 inches:



It has always looked funny to me as it has a spot where it appears to have been cut and welded....or something.

Also, the clutch was dry, no oil or anything else to cause slipping. I first noticed the slipping on the way back from our local Christmas parade. I've been driving short distances since then but didn't climb enough of a hill to detect it until last weekend. (My continuing goal is to drive it every weekend).

I had to start it in first gear and chug back into the shop bay.

Maybe that section of linkage is too short or has been modified?

[Cal_Gary]

VPW advised that the M37 clutch rods were all made with the weld in the middle. I once had one but sold it because it didn't work for me. Once I went with the Power Wagon clutch rod I was able to properly adjust my clutch. Let me measure mine tomorrow and we'll compare rod lengths. If those are close we may have to measure the height of the pressure plate fingers.
More to follow,
Gary

[refit1701]

The thought of dropping the tranny or pulling the power pack makes me dizzy. I'd make an adjustable rod if need be.

[Cal_Gary]

Hence the Power Wagon clutch rod:
http://www.g741.org/PHPBB/viewtopic.php ... clutch+rod

Gary

[refit1701]

If those clevis parts are the same size as the brake and shifter, I have some spares I can make one with.

[jim lee]

Here's mine. I just remembered I had a picture. Don't know if this helps or not.

It looks like ours are swapped from on another top to bottom.



-jim lee

[Cal_Gary]

Just measured mine and we're close-mine is 4 3/4 from center pin to center pin. Started raining so I couldn't check any other parts of the linkage. You might get away with dropping your bottom pan in order to check the travel on the throwout bearing before pulling the tranny.
Let us know once you've checked further.
Thanks,
Gary

[refit1701]

I'm beginning to think that there is some thing fundamentally wrong with the pressure plate. Though I won't be able to do any work on it till the weekend. I have a spare which I am going to look at. A longer pushrod may only bandaid the real issue.

[jim lee]

Unless they changed things, I think your linkage is upside down.

It looks like both pictures are taken looking up at the linkage below the cab floor. On mine, the pushrod is hanging down below the shafts. On yours the pushrod is above the shafts.

-jim lee

[refit1701]

Your photo is from under the pedals and appears to show the brake cylinder push rod leading out of the image to the right. Taken from outside the frame. My photo is inside the frame looking at the opposite end of the pedal shaft with the bellhousing just out of sight to the right. So I think we are looking at opposite ends. Everything on the linkage is keyed so I don't know how it could be wrong...though I did inspect it the other day.

Without the .125" spacers, the throwout bearing does not travel far enough forward under pedal pressure to touch the three fingers of the pressure plate.

It doesn't surprise me that this would come up five weeks before our first show of the year.

[T. Highway]

Hi John,

There are several things that you would need to look at but here are a couple to start with.

1.) Is there excessive play in the linkage? (Worn pins, Yoke holes elongated, etc.)
2.) When you installed the new clutch disc and pressure plate did you verify the finger height per TM 9-1840A ? This is covered on page 119. The proper distance from the flywheel to the top of the release fingers is 1.9375" +/- .031") If you didn't check this you may have to adjust the eye bolt nuts and then stake them after adjusting to get the proper setting.

I hope this helps.

Bert

[refit1701]

The clutch is working again, after we adjusted three "fingers" to the prescribed distance above the flywheel (1.93"). We made a short stick to use as a ruler inside the pressure plate assembly and managed to avoid the whole removal of the powerpack. So after two joy rides in the truck, this issue seems to be resolved. Thanks to everyone for the advise and assistance!