Hi all- I have a perplexing clutch question, but let me give you a touch of background. My '63 Biscayne is powered by a hot Chevy 292 L6 (built by Tom Lowe, here on the HAMB), making somewhere in the neighborhood of 300hp and 300lb-ft. Last year, the original-to-the-car Saginaw 3-speed died, and the Napa parts counter clutch went with it: the diaphragm adjustment straps all broke allowing the clutch assembly to fail. I had a local transmission shop install a Richmond Super T-10 and a new heavy duty clutch that was fit to the original-to-the-car but freshly machined and balanced 153T steel flywheel. Driving it last summer, I noticed a gradual increase in vibration in the car as engine speed increased. At first, noticed vibration at around 4500RPM, then 4000, then down as low as 3000RPM. On the last drive of the season, in October 2014, I was accelerating onto the freeway when I heard a "crunch - zing - tinkle,tinkle,tinkle" noise in the bellhousing. I drove it 5 miles home and put in the garage for the Winter. Fast forward to yesterday, when I got the car back to the transmission shop that did the install. It turns out the same clutch failure has occurred - all of the diaphragm adjustment straps have broken. My shop hasn't ever seen this happen outside of missing a shift at high RPM (i.e., intending to go from 3-4, but going 3-2 instead) - which hasn't happened in this car. While I enjoy driving it kinda hard, I certainly wouldn't say I've been abusing the motor, trans, or clutch. We're kind of at a loss for the root cause of the failure. If you've encountered issues like this before, or know of possible solutions, I'd sure appreciate it if you could share your wisdom. Thanks in advance.
Me too. I am going to be honest while 300 ponies is pretty impressive for the 6 it is not impressive enough to be eating clutches. No offense intended. I have run them but never really cared for a diaphragm pressure plate a 3 finger is what I prefer if I have a choice and borg n beck makes a good product.
If it chewed the diaphragm in the area around the throw out bearing I'd suspect that to be the root cause. If it's further out near the pivot area I suspect it's making contact with something it shouldn't. But that would make some serious noise. Another thought is your clutch may be over traveling passed it's ideal release point. Might need to reduce your pedal ratio or add a stop to it. Diaphragms don't like to be over traveled like that. If you have had to make multiple clutch adjustments, it would be indicative of bending the fingers inward.
Over travel on the clutch- man what a problem to have there. Most guys can't get enough travel and the damn thing is so heavy. Since 2 clutches went the same way, it should be easy to find the problem.
Two different transmissions and same failure and you mentioned vibration I would look at the pilot bushing or lack of one.
Pilot bushing was replaced when the motor went in the car...should be good, but we'll double check it.
This seems to be the thought - too much travel on the clutch. The original clutch in the car was the three-finger type, and since the three-finger Borg and beck style needs more travel, it might well be a linkage ratio issue.
Yepper. Subbed out to Proven Force, a very reputable local shop that matched the clutch, TO bearing, and did the machining on the flywheel. Good point though.
Not sure, but both clutches were matched as a set with pressure plate, clutch disc, and throwout bearing.
Thanks for the prompt. After some lengthy discussion with the transmission shop, we moved to a custom (due to size) Borg and Beck-style pressure plate. The rotational forces, wherever they originated, that destroyed the old clutch won't affect the Borg and Beck plate. I've put about 150 miles on the car so far, and all is well. Plus, if you're in Minnesconsin, I'll give a shout out to Certified Transmission in Stillwater - they definitely treated me well during all this.
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