I need help. I am an ASE certified mechanic who is restoring a 1971 LS5. I just put in the original 454 and when I did I put in a new clutch, pressure plate and of course the pilot and throw-out bearings. The problem is when the car warms up it becomes increasingly difficult to change gears. Reverse gear is impossible and third and second gear are very difficult to engage. I have tried everything I know to do and a lot of things other people have told me. I went so far as to "shim" the transmission 1/8" away from the bell housing just in case the in-put shaft of the transmission was getting hung up on the pilot bearing as it warmed up. This board has been a life saver in the past and I know if I can get the right answer it will be here. Thanks in advance.
-
-
Re: LS5 Clutch
First thing that comes to mind with all that you have done is that there is a possibility that you may have the wrong length of throwout bearing. If it is to short you would encounter the problem you describe. -
Re: LS5 Clutch
P.S. Since you are doing this all yourself, perhaps you still have the old throwout bearing. If you do match it to what you know is the same type that you installed in the car before you pull the transmission to verify. I would hope that no one would of looked at both style of throwout bearings and they got put back in the wrong boxes and you got what you believed was the correct one.Comment
-
Re: LS5 Clutch
Tom, It sounds like this only happens while the car is warming up. Is that what you've meant to imply?Comment
-
Re: LS5 Clutch
Tom------
I don't understand why this problem occurs as a function of the temperature state of the engine, but it would seem that for whatever reason, the clutch is not disengaging properly. Perhaps it is marginal when cold and when things heat up and, consequently, expand, you get "pushed over the edge" into the problem area.
First of all, as I have mentioned previously, clutch adjustment on Corvettes can be VERY tricky. Very often, when you have the specified amount of pedal free play, you will not achieve full disengagement of the clutch at maximum pedal deflection ("floorboard"). Usually, I just try to achieve "some" free play so that I get full disengement of the clutch at maximum pedal deflection.
Also, and related to the above, I've found that since the Corvette clutch system is so difficult to adjust, the correct clutch system geometry is absolutely critical. The only way that I know of to achieve this is to use GM clutch components. In fact, even flywheel resurfacing can change the geometry enough to put you out adjustment range. I don't like resurfaced flywheel irrespective of this, so I usually replace rather than resurface a flywheel. The correct GM components for your system are as follows:
pressure plate assembly--------GM #3884598
flywheel-----------------------GM #3993827
release bearing (1-1/4" long)---GM #908244
fork---------------------------GM #3887177
ball stud (1-1/2")-------------GM #3729000
fork push rod--(8-37/64 length)GM #3872960
friction disc------------------DISCONTINUED (unfortunately)In Appreciation of John HinckleyComment
-
Re: LS5 Clutch
I have installed the throw out bearing incorrectly with the spring steel portion of the fork located outside the bearing groove. If you adjust the free play under this condition, the travel will not be enough to completely dis-engage the clutch. If you adjust the free play out and then some, it will shift better but the bearing is turning all the time and life is short. I made this mistake once in the sixties and came across a friend who did the same thing about 10 years ago. If I understood your statement correctly, this condition that you have gets worse as the grease gets hot which reduces the drag on the gears. The heavy grease helps slow the disc down because it is overriding the pressure plate drag. You cannot get full dis-engagement. Did I explain this well enough?Comment
-
Re: LS5 Clutch
I had this same problem with my '65 small block. I replaced the same components with new as you have and in addition installed a new flywheel. I did substitute the new style needle pilot bearing in place of the original bronze variety. All the parts were aftermarket except for the flywheel. The clutch dragging problem when hot has disappeared. I don't know for sure which component was the culprit, but I suspect it was the bronze pilot bearing which looked like it had been slightly peened when it was installed by the car's previous owner.Comment
-
Hey, Gene, ol' buddy!
good to see ya here!
BillComment
-
Thanks for the help!
I want to thank everyone for the input. Over the weekend I pulled the tranny and replaced the pressure plate, clutch disc and throw-out bearing with the GM numbers I was provided. Since the flywheel was new, I didn't think that was the problem. Luckily the GM clutch kit worked! I just got back from driving it over 100 miles and it shifts into all gears including reverse.
Thanks again for all the great help, I should have known to try this site first before anywhere else.Comment
Comment