The Stovebolt Site Forums The Shop Area Driveline Clutch judder insanity…

Long story, but I’ll try to keep it short. I have been dealing with clutch judder in the truck ever since day one after the restoration….so, for years. Truck wasn’t running before I bought it, so I have no idea what is was doing prior to me taking it apart. Overhauled T5 installed with spacer plate. I really want to get this last problem sorted out on my truck, as it is such a pleasure to drive otherwise.

Did all the Dial indicator checks, then replaced: Pilot bushing, clutch disc, pressure plate throw out bearing, re-shimmed input shaft bearing, pivot ball, resurfaced flywheel (again). Nothing has helped. Once the truck is warmed up, 1st gear takeoffs are a bummer. I was very, very careful last time not to stab the disc during installation, so I know it isn’t that.

The Old guy at the clutch manufacturing company looked at everything I brought him- flywheel, plate, cover, throw out bearing. He said that I should look at the clutch fork. he built me a new disc with marcel springs that have a slightly deeper bend,, but I haven’t re-installed the clutch and trans yet.

Well, I did look at the clutch fork and when the clutch pedal is pushed in the fork moves forward and contacts the throw out bearing sleeve with only one fork pin…. The pins on the fork are only slightly worn, but are evenly worn.

If this condition can cause the clutch to engage unevenly, then I may have found the culprit…trouble is, the fork looks perfectly straight to me. Could the ball socket in the fork be worn off to one side?

I ordered another used one on eBay, as 1950 Chevy truck clutch forks have become as rare as hens teeth- at least I can compare it to mine, to see of it does the same thing…

How would you fix mine? Heat it up and bend it until it engages evenly when it is installed in the truck? Once the fork pins engage evenly, should I dress them so that they are more round again?

Any help appreciated…. Thanks, Dave

How about swapping to a different fork? That would be a logical option to me- - - -they're not particularly scarce, and if the ball is worn, wouldn't it be a good assumption to believe the mating part also might have some wear? It would also be a possibility to build up the ball with hard facing welding rod and recontour it with a tool post grinder on a lathe. How about motor mounts? I've solved some pretty terrible clutch shudder problems with new motor mounts. Flathead Fords in the 1940s and 50s had such chronic problems with clutch shudder that there was an aftermarket kit sold to preload the mounts toward the rear of the car. It was most noticeable on the ones with a torque tube rear end- - - -1948 and earlier.
Jerry

That is interesting. Yes, I will install the other used fork when it shows up. Front Motor mount and bell housing mounts are all new and I even pulled the bell housing mounts out to look at them- they are fine. The cast clutch forks in the trucks have been hard for me to find. A while back, there were still some NOS ones…I should have jumped on that when I had the chance. The pivot ball is new, and my clutch fork fits on it nicely and operates smoothly without any play…but the fork cup it might be ovaled-out off to one side a sit- I can’t see it or feel it though.

I will just swap the forks and see if it improves. The geometry of the linkage: Pedal-rod-fork is not ideal- the rod pulls on the fork at a slight angle (the rod with the hook in it is not parallel to the motion of the fork when it is installed). At this point I am looking at everything… so far, I cannot see anything bent or adjusted improperly.

Thanks Jerry!

Try this- - - -Loop a cable come-along around the front of the engine and preload the assembly toward the rear as a diagnosis aid. Chances are part of the problem is that the torque tube is shoving the engine/trans assembly forward and changing the length of the clutch linkage. Once the judder begins, it will get progressively worse.

EDIT: How about rear spring bushings and/or shackles? If the rear axle assembly can move forward/aft a little, that can overcome the flex built into the motor mounts. The torque tube pivot ball could be rusted tight to the main tube and fail to slip like it's supposed to, as well. Just another thing to check on!
Jerry

I’ve got a 3600 with an open driveshaft… all shackles/bushings are new and I have long, anti-wrap spring perches that I would expect would help a little with spring wind-up.

I just discovered something else- see pic. I put the flywheel on the bench, centered the disc on it, then carefully torqued down the cover plate. The clutch fingers/levers are on not all even- I centered the throw out bearing on it and took this picture-

I used a feeler gauge under the plate- all bolts are torqued down and where the plate is bolted, it is flush against the flywheel- no gap.

I just went down and bought another cover plate, but it does the same thing- you torque it down with a new disc and the fingers are not exactly even- I am beginning to think that this is not critical, and that the only thing that matters is the dimensions right when the cover plate is releasing pressure on the disc. I really don’t know- I’m just frustrated and feel like I’m stabbing in the dark with this right now..

On a modern diaphragm spring clutch that I've installed had instructions to hammer down the fingers that weren't even. I'm not kidding. they said hammer. Mine were all even, so I didn't have to break out the hammer.

I had the same issue on a '55 and a '79. Motor mounts. When you get it back together, visually observe what the motor is doing when the clutch engages. Hotrod's chain idea is good. I fixed both my issues with new motor mounts. Do you have a tranny support cross member? Is the tranny bouncing on clutch engagement? Also check u-joints for binding; bent drive shaft.

Ya, that does sound odd, I don't think about bringing out a hammer to "adjust" a clutch. Kinda' like when putting a battery in the vehicle, batteries and hammers don't play well together.

If it were my truck, I'd try a new flywheel. Sometimes a part can get so overheated that it developes hot spots that just can't be machined out. Sort of like brake drums or discs that are out of true and cause brakes to pulsate or judder and after resurfacing, go back to doing the same thing. Or, at least, try a different used flywheel.

I am also of the opinion that the problem may be in the flywheel. Had the same issue with another truck once--could not engage the clutch without is shuddering all over the place. Had a new clutch disc, pressure plate and throwout bearing installed. Still shuddering--had the flywheel surfaced and the problem went away.

I removed the motor and bell housing mounts to inspect them- they are new and in excellent condition. It was not fun removing these!

The open Driveshaft is new. Jerry’s idea is a good one, but I have an open driveshaft, and everything is apart right now. When the new clutch goes in, if I am dealing with the same issue afterwards, I will be pulling a cable around the engine…..

The flywheel has been resurfaced twice now, installed and the run out checked with a dual indicator at multiple locations along the friction surface of the flywheel. All well within spe, no high or low spots discovered.

I have a crossmember under the T5 with a T5 rubber mount, but it was installed to try and solve the problem (it did not solve the problem), and since the consensus is that the T5 should not have a crossmember, I am goin to keep the crossmember, but remove the rubber mount when I put everything back together, so that the T5 is no longer supported/restricted.

My Clutch pressure plate fingers are not level after torquing down clutch.I found a clutch guy in Texas who understands these trucks, and I went over all of my dial indicator measurements (housing bore, housing trans mount surface, flywheel runout, etc)… and he has told me that the FLAPS made in Africa cover plates I am buying are basically crap, because the fingers should be even when everything is torqued down. We are going to install a new cover plate, disc, with the shorter style throw out bearing. The new cover plate fingers will be higher and not be completely flattened out when torqued down.

Apparently, back when we had asbestos clutch linings, these problems were less likely to occur.

I will follow up here in a couple of weeks when I get everything out back together….

With the fingers uneven, the throwout bearing is going to pick up the pressure plate unevenly. Since your cover plates are already crap, you might try the hammer thing and level out the fingers. What's it going to hurt? It may solve your problem.
[on edit] I've seen something John Milliman posted - If it's stupid, but it works, it isn't stupid.

Just reading this and I am wondering this. Can you assemble without the driveshaft installed and Test for the judder? I am thinking if you assemble without the driveshaft and you still have the problem. Then your issue is with the engine/trans. If the problem is not present then the issue is with the driveshaft/ differential, or the Driveshaft / differential are an element in the causation of the problem.

I don't know if this makes sense but this is what I would try. I also like the hammer idea!

My GUESS is that you won't feel any judder without a load on the clutch.

Doing Brian's test with the transmission and driveline installed, but tranny in neutral is the same test without removing any parts. And much easier.