1973 Corvette Rear End Problem?
 

Hello everyone,

I just started driving my 1973 Stingray again after a week of decomish due to a blown water pump and bad alternator. As I tried to get into second gear I could feel and hear a vibration. Seems to be coming from the rear, and my father said the same thing. The previous owner had this car setup for racing, has a shift kit and first gear starts to high rev at 30 and then shifts at 50. 350 cui from a 71 Elco, Carter 4-barrel carb, edlebrock performer RPM intake, MSD 6-plus ignition control, long tubes...pretty sure that the tranny is original to the car (3 speed). Anyway, at highway speeds I can still feel the vibrations. My dad thinks it might be either the U-joints are going bad, or the fluid in the rear end might be low. Tranny fluid is good, and just changed the oil. If anyone can please help, it would be much appreciated.

Thanks.

Might look at the rear wheel bearings also. Does it do when coasting? In neutral? Hard acceleration?

Might as well do that too while I'm back there. No, doesn't do it when it is coasting or in neutral. I mostly feel it when I am trying to get to second and at highway speeds.

And it didn't do this before it sat for a week? Meant to ask what's a '71 Elco?

Might check rear diff lube level also.

Nope did not do this before it sat. '71 El Camino.

Oh an I just checked the rear diff fluid level and it is good, looks like it could use a change though...

If you do decide to change, don't forget to put in a bottle on GM's Posi-Trac additive. Keeps the clutches from grabbing.

I'm thinking of getting Royal Purple Max Gear-Synthetic 75W-90, with the additive. How does that sound? Or is there a certain weight I should use?

The weight sounds right but I'd stick w/ the GM additive. I tried something one time that supposedly had the additive in it and the diff. started clunking on slow turns.

Well, something new has occurred today when I was driving home. I noticed some chatter coming from the rear-end when I was waiting at a stop light. It was faint but I could hear little clunks and whenever I made a right turn and while on the gas, the chatter was back. I put in reverse and backed up about 60 feet to see if there would be any noises but nothing. Also it feels that the differential isn't even grabbing. I was driving about 25 and the revs were going up but the car was going no where, and this never occurred before. I fear now that the entire differential is going bad. Any insight?

If you've never changed out the lube, I'd do that and put in a bottle of GM's Positrac additive. Worked for me.

Changed the rear end diff. fluid with the additive. Also got both halfshafts out and removed the old U-joints (very ugly!). Right now I am cleaning up the area and looking to see what else need to be changed. I did notice that on the driver side trailing arm that there has been metal on metal contact with were the halfshaft connects to the wheel. The trailing arm looks shot anyway, it's rusting out at the bottom. Could that possibly be a wheel bearing issue. I haven't checked those out yet. I ran the car without the halfshafts in, put in gear to see if the vibrations still occurred at around 40, nothing and the rear end sounded really smooth. But when I tried to put it in park, I heard gears grinding in the front area? Could that be the starter and flywheel, trans?

I suspect since you had most of the drivetrain disconnected, there wasn't enuf friction to stop the transmission from rolling and maybe what you heard was the Park pawl hitting the teeth. If you've ever put a vehicle in Park before it was completely stopped, it sounds the same as a bad shift on a manual tranny.