'69 Clutch Problem

[Russ C.]

I have a base model convertible. From everything I see, it's a numbers-matching car. I've had it a little over a year. From the day I got it, I knew the clutch and throw-out bearing needed replacing. Usually that's not rocket surgery. I've owned 3 other '69s in the past, a small block coupe and 2 big block convertibles, although those were several years ago. The problem is that either I can't find the right clutch kit or the linkage has been changed. After installing 2 different clutches, The problems I encountered were the clutch was not releasing the pressure plate in order to shift. It acted as though the synchronizers needed replacing, and the pedal was way out of position, very near the dash. I've had some very experienced mechanics working on it, and I had ordered the kits from a Corvette specialty company. Mine is a 10-spline transmission shaft. One of the things I have noticed is that there appear to be several different clutches (stock, not higher performance) available and it's confusing and exasperating. Any information is appreciated.

[Chris H.]

Re: '69 Clutch Problem

Russ, many aftermarket clutches don't release when they are supposed to, meaning that they require excessive travel to fully release. After much research on this discussion board and Corvette Forum, I chose a Luk stock replacement clutch for my '69 L71. I even checked it's release point in a hydraulic press prior to installation.

The two brands that released within throw out bearing travel spec were Luk and McLeod. If your z-bar linkage is not stock, all bets are off.

[Russ C.]

Re: '69 Clutch Problem

Russ, many aftermarket clutches don't release when they are supposed to, meaning that they require excessive travel to fully release. After much research on this discussion board and Corvette Forum, I chose a Luk stock replacement clutch for my '69 L71. I even checked it's release point in a hydraulic press prior to installation.

The two brands that released within throw out bearing travel spec were Luk and McLeod. If your z-bar linkage is not stock, all bets are off.

Thanks, Chris. The linkage was going to be the next thing to check. I'll admit, it's been puzzling and frustrating. I'm hoping to get this solved in the next few days. My thought is that the next most-likely thing is that the z-bar failed and was replaced with an incorrect unit. I don't know if the rest of the linkage could still be used but if the angle between the two arms is not correct, it would not permit the proper movement, or travel distance, to properly work.

[Chris H.]

Re: '69 Clutch Problem

Russ, here's a good thread. :

Some Facts and Numbers on Inadequate Clutch Pedal Travel Range - CorvetteForum - Chevrolet Corvette Forum Discussion

[Russ C.]

Re: '69 Clutch Problem

Many thanks, Chris! I know this is going to help. BTW: I don't know if I mentioned at the start, mine is a Riverside Gold 350/300 horse car. Still researching. Several years ago I had a 427/390 horse convertible, #s matching, both tops, even original spare. That was THE car.

[Joe L.]

Re: '69 Clutch Problem

I have a base model convertible. From everything I see, it's a numbers-matching car. I've had it a little over a year. From the day I got it, I knew the clutch and throw-out bearing needed replacing. Usually that's not rocket surgery. I've owned 3 other '69s in the past, a small block coupe and 2 big block convertibles, although those were several years ago. The problem is that either I can't find the right clutch kit or the linkage has been changed. After installing 2 different clutches, The problems I encountered were the clutch was not releasing the pressure plate in order to shift. It acted as though the synchronizers needed replacing, and the pedal was way out of position, very near the dash. I've had some very experienced mechanics working on it, and I had ordered the kits from a Corvette specialty company. Mine is a 10-spline transmission shaft. One of the things I have noticed is that there appear to be several different clutches (stock, not higher performance) available and it's confusing and exasperating. Any information is appreciated.

Russ-------

Proper clutch operation in a Corvette is VERY sensitive to ALL the system parts being correct. If any part of it is "off" the whole system won't operate correctly.

clutch pedal pushrod-----GM #3921654----16-1/2" overall length

clutch fork pushrod-------GM #3872960----8-37/64 overall length----discontinued

clutch control lever--------GM #3888279----158 degrees between levers----discontinued

clutch release bearing-----GM #19245400---1-1/4"

fork ball stud---------------GM #3729000-----1-1/2"

clutch fork------------------GM #3887177

I do not use or recommend the use of surface-machined flywheels. However, if one does use such a flywheel one needs to install a special shim between the flywheel and crankshaft flange which is equal in thickness to the TOTAL thickness (current + any previous machinings) removed from the flywheel.

LUK or Sachs clutches are the closest to the original clutches which are long-since GM discontinued..

[Russ C.]

Re: '69 Clutch Problem

Thank you very much, Joe! I've recorded all the information you've given me. I've got an original Chevrolet Chassis and Body Parts catalogue (1953-1982) and I had been looking through it for these parts. Your info. has helped reduce the time spent tracking all this down.

[Mark G.]

Re: '69 Clutch Problem

Maybe this might help with your diagnosis. I do not recall where I got this from.
clutch z bar dimensions.jpg

[Russ C.]

Re: '69 Clutch Problem

Thanks, Mark! I'll print this and take it down to the shop. Earlier Joe Lucia sent some good specs and one of the dimensions he mentioned is the angle between the arms. I think it's a little different than the 155 degrees in your diagram. When you think about it, that difference can make a big difference in the amount of travel in the clutch fork.

[Russ C.]

Re: '69 Clutch Problem

My apologies to Joe. I just went back to his post and the angle spec he has is the same as your diagram.