Clutch Trouble - Advice Desperately Needed

[HiEyeAmChris]

Hey ya'll. My 1970 has the Muncie SM465 (this is what the previous owner told me. I don't know how to verify so any tips on that would help). I'm going to say I'm fairly mechanically inclined and I can do quite a bit myself but am limited by tools and intimate know how. This is my daily driver.

Up to the point things started to go wrong everything was working well. Long story short - the clutch pedal began needing to be pressed harder and harder and felt like it had less and less play. Shifting became difficult and he'd try to move forward when started in gear. Then shifting into second I heard and felt a loud pop and the pedal sank to the floor. I took a look and could see the pivot stud that mates the z-bar to the frame had sheared off. I took the linkage apart and tried to manually move the clutch fork with a pry bar - it only moved about a half inch backwards and was completely slack moving forward. The clutch didn't seem to want to disengage which I had a hunch was why the linkage had snapped. I needed it fixed quickly so I took him to a local shop to have them repair the linkage and inspect the clutch. They fixed it and assured everything was working great. And it was - the clutch never felt so good and the gearbox shifted silky smooth... For about two weeks.

Now I'm back to the same story. The linkage is still in tact but the clutch pedal has essentially no play. I was able to start and drive it in third to get it home. It doesn't want to come out of gear. My research says that it's likely the clutch fork being bent inside the bell housing. Does this sound correct? Also since everything else seemed to be working well enough is this the only component I should worry about replacing at this time?

Any advice will be much appreciated!

[68gmsee]

Man, that's a good one. If your linkage (zbar,etc.) is okay and the clutch won't release, I would suspect the pressure plate first. I had one that was bad and would not release properly and I've had the clutch wear to the point where it will slip, but yours doesn't sound like normal clutch wear. I would yank the tranny out and suspect a bad pressure plate.

['68OrangeSunshine]

I have had the Z-Bar [clutch linkage-cross shaft-bellcrank] break an arm and lost the clutch pedal on the firewall and stuck in-gear or out-of-gear. Happened 3 years ago on my '71 GMC Jimmy K/1500 w/ 350V8/SM465-NP205. On that truck, after re-welding the arm back on the Z-Bar, I still had problems. It turned out the Throw-Out Bearing [T/O] was shot -- had elongated its center hole and made a racket. I had to drop the skid plate, both driveshafts, transmission crossmember, transfercase crossmember, then the Trans/Xfer case assembly, then the bellhousing, clutch fork, T/O bearing and the clutch disc and pressure plate. I wound up resurfacing the flywheel and pressure plate, replacing the clutch friction disc, and T/O bearing.
Those cast iron clutch forks are bombproof. I have never heard of one breaking and that cast iron won't bend. Fork could pop off its ball mount inside the bellhousing maybe? T/O Bearing is the weakest link there.
Recently on my '68 Chevy C/10 Stepside w/ 292L6/SM465 the lower arm on the Z-Bar broke on me on my way to work in busy rush hour traffic. (I will omit the sob story about the 90 minute wait for a tow and losing a gig.) I happened to have a spare L6 Z-Bar [they are different] on the shelf in my engine shack. So I R & R'ed the spare Z-Bar onto the L6, but had to have it in and out 3 times, to clear my headers, whacking it with a BFH and grinding in places sparingly, before it would work. Today I made some final 9/16 nut adjustments to lengthen the lower clutch push rod throw and it seems OK. For a 6 pack and 3 NY steaks to BBQ, a very old friend welded my OEM Z-Bar back together. He said GM didn't penetrate their weld under the arm originally 46-odd years ago. Too late for a recall now.
Without seeing it firsthand, my best guess is your T/O bearing is shot, but there could be more expensive horrors in there too.
Good luck.

[RichardJ]

The drawing below is from LMC's web page.

If you look at the ghost image of the frame bracket, you will see an "L" shaped slotthat the #9 ball shaft drops into and then slides to the rear. Item #13 is a special washer with a bent tap on one end. The tap locks the ball shaft in the rear of the slot.

It is easy to see that your ball shaft has slid forward and removed 1/2" from the clutch adjustment. Because your ball broke, the original nut and special bent washer is along the road somewhere.

[LockDoc]

-
This might help you identify it....

LockDoc

[HiEyeAmChris]

Much thanks for help so far.

I think RichardJ is on to something. The ball joint stud is definitely not sitting where it should be. I disconnected the linkage again but I can't get the z bar to slide back into the notch, and furthermore the stud just spins with the nut when I try to grab a hold of it. Any tips for that? The b*tch of it is that I gave them that "L" shaped washer with the components I removed. I'm going to try a local wrecking yard tomorrow to hopefully find one. It's going to be a real laugh if that solves the problem. Also the guy who worked on it changed the position of the rod on the clutch fork - what exactly is the effect of the rod being in one slot or the other?

Maybe I'm just being an optimist, but given before the linkage failed the clutch worked fine, and after the linkage was fixed the clutch worked fine I have to hope everything's okay internally.

[RichardJ]

>>I took a look and could see the pivot stud that mates the z-bar to the frame had sheared off.<<

The stud sheared off and you still had the nut and washer? ?

The ball stud has two flat sides. Turn it and the narrow profile will slide back the slot.

You paid a shop to fix it and you had the keyed, tab washer so why not just take it back to them?

['68OrangeSunshine]

With the Lower Clutch [threaded] Rod in the outboard hole, you'll get more leverage = easier throw.

[HiEyeAmChris]

Update:

I was about as lucky as a guy could be this weekend and I found a '68 in a local yard with the entire linkage still in tact. The guy only charged me $7!

That was where the luck ended. I put everything back together but the clutch pedal still sits on the floor when pressed and there is no action on the clutch itself. It seems like the fork doesn't want to move like it should - or if it is there is more trouble inside. So I picked up a new clutch - it's a job well beyond what I can do, but I found a guy in town that will throw it on with same day service for $250.

Is there anything else that I should be ready to replace once it comes apart? Anything I might be told needs done that I should pass on?

['68OrangeSunshine]

Are you sure the Clutch Fork has not popped off the Pivot Ball inside the Bellhousing? It is secured by a retaining clip [that looks like the Greek letter Omega] and if it corroded from rust might break and not keep the Fork in place. That would jam up your clutch action real good.
If I were finishing up a clutch project I would put new rubber boots on the Clutch Fork and lower Clutch Pushrod. Check the wear on your clutch swivel too. It's brass and made to wear out. Is there a Pedal Return Spring under the dash?
With a new clutch assembly [ = Pressure Plate + Friction Disc] make sure he resurfaces the Flywheel.
What happened to the first shop, whose work blew up after 2 weeks?

[RichardJ]

>>What happened to the first shop, whose work blew up after 2 weeks?<<


That's what I want to know.

When he put the new ball on, he tightened the nut with the ball slid to the rear of the slot. After operating the clutch for two weeks the nut worked loose, the ball slid forward and you lost your ajustment.

Simple as that.


In my opinion, the new parts were wrong, damaged or you installed them wrong. Take the truck back to the shop. Take all of the parts, old and new with you. Show him that the ball worked its way back to the front and show him the part that is needed to keep that from happening.

[HiEyeAmChris]

Originally Posted by RichardJ

>>What happened to the first shop, whose work blew up after 2 weeks?<<


That's what I want to know.

When he put the new ball on, he tightened the nut with the ball slid to the rear of the slot. After operating the clutch for two weeks the nut worked loose, the ball slid forward and you lost your ajustment.

Simple as that.


In my opinion, the new parts were wrong, damaged or you installed them wrong. Take the truck back to the shop. Take all of the parts, old and new with you. Show him that the ball worked its way back to the front and show him the part that is needed to keep that from happening.

I took it to AAMCO originally. It took them four days to find parts I found in two hours, and they didn't even use the right components. I'm more than upset, but the bill was relatively minor so I'm trying to just move past that and get it to someone who knows these rigs and how to fix it correctly.

As far as the replacement parts, I only used the ball stud, the seal, the L washer, the ridged washer, and the nut (numbers 9 and 12-15 in your diagram). The adjustable rod is almost at its max length yet the push rod barely rests inside the fork when the clutch pedal is up and it only moves back about 3/4" when fully pressed.

Should I be able to manually move the fork back to disengage the clutch? If so I can't.

[RichardJ]

>>Should I be able to manually move the fork back to disengage the clutch? If so I can't.<<

The clutch pressure plate has a clamping force of about 2500 lbs or more. Lets see? NO.

You push on the clutch pedal with a force of more than 50 lbs. The pedal itself multiplies that force by at least 4X, The Z-bar and the clutch arm also multiply that force.

You're mad at AAMCO because they took four days to get the parts?
My local chevy dealer doesn't carry those parts and neither do the local flaps. The closest wrecking yard is too far away and 95% of trucks there are automatic. I would be ordering from one of the truck vendors commonly mentioned here and be very happy with four days.

['68OrangeSunshine]

Too much length on the lower clutch push rod could mean you have the wrong sized T/O bearing. They come in a variety of sizes, skinny to fat. The wrong one can screw up your geometry.