C2 Heavy Shift

[Ron Green]

I am experiencing a heavy "clunk" when I initially put my C2 powerglide into gear then again when it shifts at low RPM into second gear or down shifts. I've changed all u-joints...rebuilt the rear end and replaced the wheel bearings but still that clunk persists. Any thoughts on where this is happening and how to fix it?

Thanks

[Mike M.]

Re: C2 Heavy Shift

what RPM have you got the engine idling in neutral when you shift and hear the "clunk" ? some clunk is normal. if you rplaced the u-joints, which is the most frequent cause of excess clunk, then i'd expect what you are hearing would be considered within normal limits. check service manual for correct RPM at Idle and adjust if you rpm is excessive .mike

[Mike M.]

Re: C2 Heavy Shift

PS-- worn tailshaft bushing could also cause excessive noise but wear here is unusual. mike

[Bruce Boatner]

Re: C2 Heavy Shift

Ron,

The PG on my C2 does the same "clunking" you described. I just got the car and was going to check out the u-joints, etc., but someone told me that the clunking was just a characteristic of the PG. Hey, I just found out that "whirring" at idle is normal for a PG (see earlier thread), so maybe "clunking" is too. Hopefully, we can just "whir" and "clunk" away and not worry about any "bang" or "pow".

[Joe L.]

Re: C2 Heavy Shift

Ron and Bruce-----

Like I mentioned previously, the old Powerglides weren't like the automatic transmissions that most folks are used to today. They had many NORMAL characteristics which if someone experienced in a new car they purchased today, they would immeditely return the car to the dealer for repair. Folks in the old days were glad to have them, though. They were a lot better than the "3 speed manual on the column" that Chevrolet owners had to live with prior to the Powerglide's introduction in the early 50's.

[Roy B.]

Re: C2 Heavy Shift

Starting in 1958 in all corvette and cars the PG"s had a Vacuum Modulator , the vacumm was taken from the carb or intake. It was added to the PG to cause smother shifting from one gear to the next. It made the clutch drum piston to close the clutch plates more slowly, giveing a better smoth shift. But if it leaks vacumm or losses vacumm or sucks in trans. oil it stops working and shifting gets harder or clunk bettween gears. Check to see that the vacumm to it is OK, then remove it to see if it's pulling trans oil in to it. Replace it if it's oil.