Guys:

I am looking for comments and suggestions. I have a '70 Chevelle SS 454 with a close ratio tranny and 3.73s. This car has always eaten clutches. We've always put what was considered a high performance name brand clutch in, but none lasted more than 15-20K miles before they start to chatter. It was suggested at a speed shop that the HP clutches need to be use harder to keep it from prematurely chattering. I find this hard to believe, but possible, I guess.

Has anyone had this problem?

I've always turned the flywheel, and last time had it magnefluxed and turned at a good machine shop that caters to the high performance crowd. The flywheel work was well within their means.

I was wondering if I needed to consider that the tranny shaft and crank might not be aligned - and having to look to offset dowel pins. Does this seem like a likey cause? This doesn't seem like an easy thing to do.

Any thoughts?

Thanks,
John

I will presume the disk was on the right way and that you have no oil leaks getting in there from the pan or the trans coutner shaft...

Is it possible that you have a truck bell housing with the larger center hole? You should check for bellhousing parallelism to the flywheel (couple of thousandths of an inch tolerance) and the concentricity of the hole (.005" tolerance)...

When you replaced the clutch(es), was it the disk and pressure plate, or just the disk? Did you also replace the pilot bushing?

Just trying to dig a little background ....

Ron:

Yes, thanks for asking the questions. You need to understand the situation to help out.

Correct, no oil leaks. Well, at times we did have one, but mostly not. I've had the car since '73, so a lot of history.

This car is stock. So, I'm guessing that the bell housing is correct - not from a truck.

I'll check for parallelism. This could certainly cause the problem, as you suggest. Right now the engine's on the stand. So, I'll have to get to it when I'm getting ready to drop everything back in.

When the clutches have been replaced in the past, the clutch, pressure plate and pilot bushing were always changed. The last two times at least (I know this for sure) also included the flywheel turning.

Thanks for helping think this through.

John

There is a minimum thickness for the flywheel. You need to check and see if you are getting close. Check the clutch linkage and make sure the parts are doing their thing, not twisting, bending or operating at weird angles. I had a clutch arm that was cracked, gap would open when depressed and wore the disk weird.

graemlins/thumbsup.gif graemlins/thumbsup.gif

The other thing that nobody has mentioned is ... how are you driving it ??? When I used to race my 71, I would be doing a clutch about every 8 trips to the track. Got real good at bench pressing a Muncie. Any kind of hard driving in a heavy car like a Chevelle will end up killing the clutch. Also, a lot of guys "ride" the clutch too much. The only time your foot should be anywhere near the clutch pedal is when you are shifting or starting from a stop. The guys at the speed shop are somewhat correct. Any clutch will tend to glaze if it is slipped too much. Get your foot on and off the pedal quick.

Guys:

Thanks for the comments. Wally, the thoughts about the flywheel not being thick enough is something I'll check on. I would have thought the machine shop would have checked (or maybe I did last time around - I forget). Also, this eating of clutches has been a problem since we got the car at 43 K miles. The linkage to the clutch could be the culprit, too. I'm guessing that I'll just change a lot of that right out - it's original, still. Do you guys have any suggestions on aftermarket linkage parts?

BillK, I don't ride the clutch at all. With the close ratio, you have to do a bit more slipping than with a normal gearset, but I get the clutch fully engaged pretty fast. I never ride the clutch - my foot stays on the floor. The speed shop guys claimed that I didn't slip the clutch enough and that I didn't do enough hard takeoffs. They felt that the clutch needed to be beat on more than I did with normal driving. I find that hard to believe. Any thoughts?

Thanks again,
John

The comment that you clutch needs to be driven harder is not correct. Clutch chatter is generally a result of hot spots on the flywheel or glazed spots on the disk. This is caused by a clutch that is over heated. Its not hard to overheat a stock type clutch. They use an organic liner that is great for smooth take offs, but it can easily be over heated.

I would suggest checking the bellhousing alignment. This is critical to the proper operation of the clutch and transmission. This is the reason that all NASCAR engine builders include a bellhousing and clutch package with the engine. Each bellhousing is perfectly alligned and pinned to the block.

Andrew

My BBC was eating clutches,p plates, tranny gears, and most everything else fed to it. I ended the back breaking turmoil and did something I should have done a few years before. I got a TH400 built for racing,manual vlv body,reverse pattern. My hungry BBC has not ate it "yet".

If the clutch disc you're using has a center hub with damper springs, check the springs. If they rattle, or otherwise seem loose, you may want to think about a solid hub clutch disc. You'll lose the cushion they afford on initial clutch application, but there won't be any springs to lose tension and cause the chattering you're experiancing.
Clutch disc selection has to be determined by the individual and the type of driving you're going to do. If you want smooth, easy clutch application, go with the springs. If "you" can be in total control of the disc application, go with the solid hub.
Back in the days, there were clutches that were termed to be "jack rabbit clutches." These were the discs with no damper springs in the center hub.

Another driving habit question: Do you downshift through all the gears when coming to a stop? The more you use it, the more wear you're putting on it. You should be using the brakes to bring the car to a stop, not engine compression.

An alignment problem would more likely cause cracking and breaking of the friction disc in the center around the splines. It's still worth the time and effort to check it especially since the engine is out, but I don't think that's the probelm.

Make sure you're using the correct bolts when installing the pressure plate to the flywheel. I saw a guy use some bolts from a hardware store a few years ago. They had shoulders on them that caused them to bottom out before the pressure plate was seated and it caused him to burn up a few clutches. Use the correct hardware.

Also make sure the new friction disc slides easily over the input shaft without binding. Use some emory cloth or a fine file to dress the splines if you have to so that the disc slides over the input shaft with minimum effort. It doesn't hurt to put a little white grease on the splines. Just don't get carried away with the grease. You don't want it slinging onto the clutch assembly.

There were a lot of good questions, and I'll try to answer some.

Andrew, I've never had a stock clutch in the car. The last clutch was a McLeoud (sp?) with the centrifugal weights. Every clutch I've had in the car since 1973 has been a HP clutch from some manufacturer or other. They all ended up chattering after some amount of time - often within a year. The bellhousing alignment has been my working theory.

Patrick, a TH400 might solve my problem, but I love the manula and love the rockcrusher! Have you ever driven with one? The sound of the engine and tranny under full throttle is something else.

OH, yes, my clutches have had the damper springs. If this was just this cluch, or I'd been using only one brand/model, then I'd consider the springs as a possible problem. But this has been a recurring problem with many different clutche brands.

Randy, I used to clutch it down through the gears to a stop, but don't really do that much now. I realized that the brakes had a reason for begin there. So I'm a brake person now.

I'm pretty sure I'm using the right bolts. I think I got new ones from the guy who bbalnaced the engine, and they were identical to the ones I had taken out. But, I can check them easy enough to make sure.

I can also check for the disk sliding smoothly enough.

Thanks for the comments & opinions, I appreciate them greatly.


The new clutch I bought a year ago (but have not put in yet) is a Centerforce II. It does have the springs. It's not the dual friction one. The model # are disc: 384148 and PP: CFT165552. Has anyone had good or bad luck with this clutch?

Another question, I figured that I'll probably just put in a new flywheel. Any suggestions? This is a '70 360HP 454 Chevelle with a rockcrusher and 3.71 gears.

Thanks again,
John

Have all the clutches you have tried been borg and beck style? If so, I think you will like the diaphragm style CF II. It is the one I run and it cured my chatter issues after switching from a hays street/strip... mind you, I have much taller gears than you do, but hopefully it will help.

I had a dodge truck once that ate clutches and I like to never figured it out and come to find out the guy that had it befor me didnt put a pilot bearing in it.I figured If the pilot bearing was missing it would make a noise or something but it didnt.Id say thats not your problem though.I just read the post and it reminded me of that old truck. smile.gif

What about break in?

Some clutches have a strict break in period.If it is not adhered to, then it may result in premature wear.

The new centerforce you mentioned should have break in guidelines.

Do you scuff the disc with fine emory before installing or do you put it right in?

Also check your clutch pedal free play. If the clutch does not fully disengage, then it will prematurely wear out the clutch.

-Oh and if you get a different flywheel make sure it is for the four five four. I believe they are balanced differently from the internally balanced big block flywheels.

Good luck.

Doug E

Bow_Tied, Yes, I've always run the diaphram style. But, I hope my chattering problems go away with this clutch, too.

Crowenate, Yes, I've always put in new throw-out & Pilot bearings.

Itza66, Nope, I never broke in any of the clutches. You may have something there. I was easy on the new clutches for a while, like with new brakes, but never did anything before the installation. Thanks for pointing that out. I haven't installed the new clutch yet, so this is good timing.

And, yes, I know about the unbalanced flywheel for the 454. But, thanks for pointing this out. I know too many people who've made this mistake.


Another question for you guys, do you know the weight of the original flywheel? Oh, I guess I can figure this out, since it's out of the car now. Also, will any brand do? I was going to jsut go with a Centerforce. Does SFI certification mean it will resist joining me in the passenger compartment, or will it simply not come apart for anything under a certain RPM, say 6000 RPMs or something?

Thanks again,
John

Just a thought...don't think anybody mentioned it but yrs ago had 68 SS that ate clutches until i put a straight edge across the flywheel and found it to have a dip in the middle of it .This is even after turning it :eek: I'm talking very little dip. Just thought I'd mention it

Originally posted by Red 70 SS454:
Just a thought...don't think anybody mentioned it but yrs ago had 68 SS that ate clutches until i put a straight edge across the flywheel and found it to have a dip in the middle of it .This is even after turning it :eek: I'm talking very little dip. Just thought I'd mention it Thanks, that's interesting to hear. I think I'll be swapping out the flywheel this time out, just to be safe.

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Originally posted by dyno jonn:
Here's the cure. Just be sure you got deep pockets. It'll last a lifetime.

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I reached my limit. It's your turn. Jon, we think alike. I considered this setup for my rebuild in 1986, but decided I didn't want that much flywheel effect. I figured it would slow down the shifting. It does look tough, though!