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C2 Clutch Shudder

I have a 65 327/350 A/C Convertible that I've had and babied for 25 years. A stunning show car. I finally had the engine out for a rebuild last year and had the transmission rebuilt too with a new clutch. I've been through 3 clutches in less than 200 miles. Each one with the same problem. A terrible shudder when the clutch is let out. When I have to slip the clutch to get up the incline of my driveway and slowly go into my garage, it vibrates like it's going to shake itself apart. After the third clutch was put in, the transmission guy told me it just needs to break in. This does not seem normal. I did not have that problem previously. The brand of clutch that was installed was Luk. I was told that the flywheel was machined. And an engine mount replaced. Anyone have any ideas?

Submitted by: Jeff Menkes


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Thanks for all the suggestions. Update, I took the car to a Corvette expert. Carl Pugh, at Corvette Mike in Anaheim. Carl is the best with C2's currently living. Put a new clutch in properly. Had the flywheel machined properly. Adjusted the shifter linkage. And it is now perfect. So $1000 to fix a poor $1800 transmission and clutch rebuild. Live and learn. Drive the distance and go to a Corvette pro. Not a transmission shop. Jeff Menkes on 4/9/2015 6:54:57 PM
I think you?re looking at the wrong parts. Here in the shop we have ceased machining flywheels unless there is absolutely no alternative. We have had so many problems (mostly like yours) that we consider it cost prohibitive. When a flywheel is machined it has to be absolutely perfect or the clutch will shudder. Consider that when you set the flywheel up in the lathe that it must be checked multiple times to be sure there is no run-out. In most cases this requires a mounting hub to bolt the flywheel onto. That hub has to have as close to zero run-out as possible and is often measured on the order of one ten thousandth of an inch rather than one thousandth of an inch. As little as one thousandth of one inch at the center of the flywheel can equal several thousandths of an inch at the outer edge of the contact surface. To understand the principal for all those who were not trig masters in school put a ruler on your desk and lift one end while the other rests on the desk. As you look at the gap you see it increases as you move farther away from the point where it touches the desk. This is the same thing that happens when you have a tiny variance at the center of a flywheel. So remove the tranny again and measure run-out relative to the crank shaft and don?t be surprised if it exceeds the allowable limit. If the run-out is out of spec remove the flywheel and carefully check the end of the crankshaft including measuring run-out and any signs of nicks, dents burrs, etc. Posted by Administrator on 3/27/2015 3:08:16 PM
I'm told the throw out bearing and pilot bushings were replaced. But I can't swear to it. Jeff Jeff Menkes on 2/9/2015 3:59:02 PM
Thanks for the help guys. I thought the break in period was nonsense. Total cost for the transmission (and clutch) rebuild was $1800. So definitely not a quickie cheap job. I may have to go out of my way and take it to Corvette Mike in Anaheim. Cheers, Jeff Jeff Menkes on 2/9/2015 3:56:34 PM All answers that you received were good. Paste the link above into your browser for more Ideas. Ron Marino on 2/9/2015 3:52:06 PM
Sounds like the flywheel may need to be re-machined. The throw-out bearing would make a whining sound and you probably would feel it in the pedal. There is no clutch "break-in" period that I've experienced. Edward Mankowski on 2/9/2015 3:41:28 PM
A shudder on clutch engagement is not normal or in need of a break in. I highly suggest consulting with a well known and competent Corvette technician on this before the rear main seal is compromised. Questions to ask are: (1) Was the pilot bushing replaced? (2) Was the throw-out bearing replaced? (3) Was the flywheel checked for balance after being machined? (4) On replacement, was there any evidence of fluid leaking from the rear main seal or the front transmission input seal? (5) Was the thrust clearance checked when the engine was rebuilt? (6) Was the pressure plate balance checked? (7) Was the flywheel machined too thin, ergo: causing the clutch springs to contact the flywheel bolts? (8) Was the front input shaft bearing replaced on transmission rebuild? For now, I think that should get your diagnosis started. It may be necessary to straighten out one or more of the items I mentioned as you move toward a resolution. Personally, I would change the clutch from whatever 'LUK' is to a NEW GM clutch. No rebuilt! One other word of caution: this is a Corvette, not a Toyota. Do not go for the cheapest price you can find. All my best wishes. Tony Rogers, Retired President of the Rogers Automotive Machine Shop Corporation and a current Corvette owner. . Tony Rogers on 2/9/2015 3:39:37 PM
Check the engine and transmission mounts and also check the body mounts. I had the same problem in an old truck but new body mounts cured the problem. JAS346 on 2/9/2015 3:33:15 PM
Was the throw-out bearing replaced? Robert Snyder on 2/9/2015 2:58:24 PM

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