SGDADDY69

Just finished a BOF restoration of 66 427/390 hp. coupe. Has NOS flywheel, new clutch and pressure plate from Centerforce, new throwout bearing, and new pivot ball on bell housing. As I let the clutch out, especially in reverse, the entire car shudders, When the clutch is fully engaged the shudder is gone. It occurs with just the first 1/4-1/2 inch of clutch pedal release and then disappears. I have loosened and retightened every nut and bolt in the entire drivetrain including the motor mount bolts to no avail. Also R/R'd the tranny fluid. Still shudders. I know I'm probably going to have to pull the transmission but need to know specifically what to look for. Any thoughts would be appreciated

midyearvette

if the nos flywheel is dialed in ok, (flat) check the bell housing alignment
sounds like you may have a bad unit from centerforce or a warped disc like maybe the trans hanging on it during installation??

thoyer

Grease or oil on the clutch or flywheel?

Warped clutch disc?

Was the flywheel resurfaced prior to install and checked for flatness / runout?

Flywheel / pressure plate not torqued correctly?

How does the car run otherwise? Could be a tuning issue showing up due to the increased load during the clutch engagement.

Just a few thoughts.........

Let us know what you find.

Tom

tuxnharley

Any chatter would be magnified in reverse due to the lower gear ratio there, so that may not be significant as to the cause of the problem. It sounds like your clutch is not entirely gripping, but is slipping/chattering a bit in the process of engaging.

Given the list of things you have done, a few thoughts come to mind:

- was the flywheel checked for runout, and or given a light truing/surfacing to increase the initial "bite"?

- is there any surface contamination on the flywheel/ clutch disc/pressure plate surfaces? traces of oil, grease, or even finger prints can cause a problem. A wash with a clean rag and denatured alcohol before installation is a good idea.

- in any case, I'd give it a few miles and some hard shifts in the upper gears before pulling it apart. Sometimes it just needs to seat itself and/or burn off any contaminants. No guarantee that will work, but with all new parts it's worth a try!

Good Luck!

Dennis Beck

I have a Centerforce clutch #OF735552 behind my zz383. We had to use a Centerforce flywheel #700170. Would this apply to your application?

Dennis

SGDADDY69

The flywheel was NOS GM(even dated correctly for my car for what that's worth).I wiped it down with laccquer thinner but that was all. No resurfacing. During installation I thought every thing was clean. You never know for sure. I guess I'll just bite the bullet and pull every thing out again. Pull the flywheel look for hot spots but have it resurfaced regardless, and thoroughly check the clutch plate and Centerforce unit. Thanks everyone for the suggestions. I'l let you all know what I find. Tony

SGDADDY69

Not sure. I'll have to cross reference the numbers. Thanks. Tony

Dennis Beck

My point is does your Centerforce clutch require a Centerforce only flywheel?

Dennis

SGDADDY69

I don't believe so. If this were the case I cetainly would have hoped that Centerforce would have indicated that their units require a matching flywheel. I'll look into that a little further. Thanks. Tony

hedgehead

Been through this with a stock unit, brand new, be prepared to swap it out. It happens.

Kerrmudgeon

Just a thought here, but if you used a ceramic HD or racing style clutch, they are prone to chatter, especially when cold. The big block 68 I worked on has one and I thought the trans was toast, but it was just the ceramic clutch. After it's heated up it's fine....

00fxd

How many miles on it? It may wear in a bit ...?

DansYellow66

I bought a brand new Hays fly wheel years ago and it had a lot of runout right out of the box. So do check the flatness while mounted on the engine with a dial indicator set to read about the center of the disc engagement area. Another possibility is a warped disc which may have happened if you hung the transmission on the disc while working it into position. A couple of 3 to 4 inch dowels in the upper transmission holes of the bellhousing works well to support the transmission while it is slid home into the clutch and pilot bushing. A broken motor mount can contribute to a shudder or chatter - but if this just happened after a clutch change it's unlikely a motor mount also went bad at the same time. Also tightening the pressure plate bolts in an uneven fashion can distort the plate and result in chatter.

Some things to check.