i don't know how or why I get into these situations but they seem to find me
68 GTS 383 4 Spd. Owner took it to a shop as he felt the clutch was slipping. One of them selected a Mcleod Diaphragm street level clutch and installed it. When he went to pick up the car, the clutch chattered violently. Its the only word I can think of to describe how it came in to me. The shop tried several different things including modifying the clutch linkage. I do not know if they resurfaced the flywheel or not After several attempts to correct the problem the owner became frustrated and took it to another shop.
They resurfaced the flywheel to a Mirror finish ( Never seen that before?) And proceeded to install a new LUK diaphragm clutch and disc. They reworked the Z-bar and mounts again. it appears to be functioning but is not straight across. They also tried several different things and gave the car back to him at no charge.
I did a little tuning on the motor as it was running poorly and missing.
It definitely helped a bit but the chatter is still horrible and violent. Think of rear bad wheel hop, but worse
So far I have done the following:
1. Checked the motor and trans mounts. The trans mount is a bit soft but still in 1 piece. Cross member is tight
2. Removed the Override spring
3. Adjusted the clutch as it was way to high and not releasing completely (PP was actually preloaded a reasonable amount).
4. Checked all the rear spring bolts and mounts. He said they were replaced about 7 years ago with springs from espo and urethane bushings. Everything was tight and all the spring clamps were in place and tight.
5. Checked Crankshaft endplay (.007)
6. Checked pressure plate clearance at 6 places. All at .057 with feeler gauges
7. Checked clutch disc runout. All seemed even again at .057 with feeler gauges.
8. Checked the bellhousing as best as possible in the car
9. Checked the bellhousing bolts
I have not checked the pinion angle yet.

This is happening in forward and reverse while trying to let the clutch out normally from a stop. Once moving the owner says it's fine (not sure if that includes downshifting?
taking off in second (3:91's) helps but have to slip the clutch a bit.
The only thing I've noted so far is the mirror finish on the flywheel which I've never seen before
In closing, The wife commented that she could visibly see the back of the springs reacting to the chatter.
Any ideas before I pull the trans and clutch ?
TIA

Could a polished flywheel cause the disc surface to become "glazed"?
Aren't they supposed to be machined and not ground?

I’ve had two customers come in with the same complaint that hated there diaphragm clutches. I changed them both to the OEM Borge and Beck design and they left smooth happy. I won’t install a diaphragm in any car I work on. Some people like them but I don’t. The ratio of the clutch release for a mopar is too fast for a diaphragm. Sounds like he’s got several problems envolved here.

I have had poor results with the diaphragm clutches also. Other guys I know have had good results with them, I think you are onto something with the surface of the flywheel. Maybe a contaminated clutch disc?

Have to wonder what kind of 1/2 azz shop installs a new clutch without resurfacing the flywheel.30 years a a master tech and never did that since I was like 20 and had no $$$ etc.As for a diaphram we run them in our cars.Mine 20 years and counting behind my built 440.Sons in his built 360 truck has been in forever but just started driving this year when he got it out of storage.We run CF setups and never a problem Have installed them in other Mopars also and they work.Id say flywhell is the problem as that is what mostly causes chatter.

Every 4 speed gm I've worked on with diaph. was like that, the one car has been through 3 of them. Some of them not bas bad as others. Get that p.o.s out of there and put in what the Chrysler engineers. put in there. Is my 2 cents. Its not the finish, my buddys L34 70 Chevelle has been ground every time. I have done a few in my brake lathe for other apps and they were fine.

That being said, you could refinish/grind, and try another brand, I would like to try a centerforce next in the Chevelle.

If you really pay attention, Diaphragms all do it to some varying degree.


There is some bias hidden in there.


p.s. I typed this before saw the last post.

Interesting - I've never had a problem with diaphragm clutches, or B&B - main difference to me was the B&Bs have higher pedal effort.
I like Centerforce for diaphragms.
Mirror-finish flywheel is something I've never seen; seems to me that would cause slippage, then heat, which would then accumulate disc-material deposits, then chatter.

If the flywheel had burned hot spots before grinding that could be your problem. Those spots get case hardened DEEP into the face so even after re surfacing they are still there even if you can’t see. I’d get a new wheel, case closed. Had the problem in my 64 (b and b) thought the dash was going to break, new flywheel, fixed,

Anyone replace the pilot bushing? Like others, the flywheel finish is too smooth to me. Also, the clamping force of the pressure plate may be weak. Another thing: is the disc flat with no Marcel? Marcel is the wavy spring between the linings. If it's flat, uncompressed, you can't fart around on working the clutch. In or out, no slipping. If you see the wavy spring between the linings uncompressed, its got Marcel.

The problem isn't a diaphragm clutch, been running them for years with zero issues in place of the overly stiff OEM setup. I got three daughters, teaching them to drive stick was much easier lol.

Odds are it's the flywheel as others have mentioned. We already know a "mirror finish" is the wrong one for a flywheel. Now what damage that may have caused, to the disc, well you will have to inspect and make that call.

With this setup I would assume nothing was done right before you got it so go from that position and fix what we know is wrong, then test.

Some other things to check that come to mind. Is the car using all of the components, other than clutch assy, that it came with from Ma Mopar? Or is it a mix and match? Did someone swap in an a-body A engine trans in and not know that the B engine trans use the larger from bearing retainer which is bb/hemi only? Giving you hotdog in the hallway since the A trans uses the smaller retainer therefore trans to bell housing alignment is not happening.

Going to have to comment here, later A bodies used the large retainer, think A833OD. You can easily swap in a large retainer where the small one used to be., I believe both Brewer's and Passon have them.

But you hit on a good point we know someone has monkeyed with the linkages in a effort to fix the problem, that might be part of the issue as well. However, his plate departure numbers look good so maybe not.

Had the same problem recently and it turned out to be a dry pilot bushing.

First off, a bigthank you to all that replied.
The car is an original big block GTS
*My understanding is the 1st shop DID NOT resurface the Flywheel when installing the Mcleod
clutch.
*The second shop did with the LUK clutch.
* Both shops monkeyed with the Linkage/ Z bar.
*There are 2- Z bars in the trunk along with a multitude of linkage parts/mounts
*I have installed over a 100 Centerforce clutches in a many different Pre 1980 makes and models with only 1 issue. Long story but once it was removed the issue was apparent and an admitted error on their part
* I also have never seen a mirror finish on a flywheel. New, Used, or Resurfaced. I do know "Street Clutches" normally require a 500 or so miles of normal driving to break the clutch in. This, was taught to me years ago, this wears the rough surface on the PP & FW down while transferring clutch materiel to both.
*I thought possibly this was a new technology or something applicable to Race only applications
*Good thought on the input bearing retainer, it is the correct one. Had more than one bit by that one on chevy's. One was quite funny as I suggested a blow-proof and said owner said no as it was a #'s matching car, 6 mo's later it needed a new trans due to the mentioned issue. It BTW had a truck bellhousing with a larger opening 🙄 🤣

What really Dyson's(keeping it clean,LOL) is I have 2 new clutch assembly's with less than 25 miles on them and I can't use either with any level of confidence.

My thoughts at this time are
1. Try to seat the clutch in by taking off in 2nd or 3rd gear without getting it too hot. Or
2. New PP, disc, flywheel and clutch linkage
I'll attach a few pic's of what was in the trunk. I should mention there is another hacked up clutch linkage still in the car I did note inside the Mcleod box was a warning label (see pic below) . I do not know if it was better, worse, or the same with that clutch. But at the present time I would anticipate spot welds starting to break within a very short time.
IT IS THAT BAD.

Any other thoughts, opinions or input is welcomed

How about a picture of the Zbar set up on the car?

I went to McLeod's site and looked up the instructions



And, maybe also relevant

The first thing I would check is the runout of the flywheel. The only thing that usually causes chatter is warped surface or hot spots on the flywheel. You also need to check the surface of the crank flange for runout. This is unlikely though because from what I read from the post it was only slipping with no chatter. That PP you have in the picture looks fine to me because I have run worse than that before with no chatter.
I would try another "known good" flywheel if you can find one. I have also seen this issue when someone let the transmission hang from the bell while searching for the bolts, it had warped the hub on the disc.

Gus

here's a few, it' functioning but misaligned . As near as I can measure in the car,
the lower arm to the clutch fork is about 4.0" center of the pin to center of the tube.
the upper is about 5-5.5". It's hard to get and exact with it in place.
The availability of replacements appears slim. I am hoping either someone can confirm the measurements from a known BB z bar or possibly have one they can part with. Right now i don't know what I have

Originally the owner thought it was slipping, the Chatter started after the replacement(s) . My concern with using the PP & disc is if there is an issue I get to change it again.

Thank you, hadn't had a chance to do so but confirms what has been said. I'll attach a pic of the flywheel wher you can clearly see the reflections of the PP