Rear suspension help on the 67.....
 

So, I tried to make it to a Corvette gathering tonight, but had to turn around and head home...

To describe the problem, there's a very loud "clunking/grinding" sound coming from the rear, when turning, either towards the right or left. I think only with a load on it, when coasting around a turn or driving straight no noticeable noise. But the car has side pipes so it really hard to hear....

Half shaft U joints? Drive shaft U joints?

I limped home but made it.....The problem grew worse, the longer I drove, or as it got hotter???

Not sure if the joints are originals, with or without grease fittings....?

My thoughts....because the issuing is occuring when turning either way,I think it's safe to rule out the U joints and concentrate on the rear differential. What is the recommended weight of the fluid. GM fluids i understand are the best brand, and I have a friend with a few bottles of the old whale oil. I will get the car on the lift later today to check the stubs for movement/play.....

Sounds like it needs a diff fluid change and the posi additive. In experience, the additive cured the "clunk-bang" sound.

Here’s the stuff Ron is talking about:

Take care,
Steve

If grinding on turns I would check the rear wheel bearings and the "slop" that may be in the differential stub shafts......and of course the U-joints... Wouldn't hurt to check the trailing arm bushings and strut rod bushings. Its possible (but not my first choice) is that the clutch plates in the differential are binding - so yes a fluid change with the friction modifier additive might be worthwhile; then go out and do some figure-8s in an empty parking lot and see what happens.

Thanks guys!

I got the car up on the lift and after a thorough inspection, I discovered fluid leaking from the drain plug pretty badly…. Must have been a piss poor mechanic that didn’t completely tighten the bolt down….

Everything else looks good. A few U joints I found to have zert fittings so they aren’t originals. There is no excessive play in the stubs or arm bearings. I’ve ordered the 80/90 and have a friend donating the REAL additive. I’m now thinking I might be getting off easy with this one! A few days and I’ll be in the lot doing those figure 8’s!

While you're under there it wouldn't hurt to look at the snubber bushing and retorque the differential bracket support bolts.....here are some specs for you.

Thank you Mr Frank! I’ll check these areas better!

That's a nice assemblage of torque values, Frank. Guessing you compiled it for your '63?

Live well,

SJW

I can't take credit for that list, somebody complied it years ago and like many things in my tech library I can't tell you who. However, I've had occassion to "beat" the values in the document against shop manuals several times and the settings recommended are spot on.

I'm aware that at least a few torque specs changed a bit during the mid-year run, so it does make sense to cross-check most of them against the AIM and shop manuals. Thanks, Frank.

Live well,

SJW

Quick follow up…. The fluid exchange worked like a charm! The best way to describe it now is, “silk”! It’s a completely new feel to the rear and handling overall. After the exchange and inspection of the chassis, I took it out to an empty parking lot, and made those infamous circle 8’s! Then hit the roads for a nice 35-45 minute drive to get it warmed up.

Smooth as silk!

I think you may have dodged an expensive bullet.

Take care,
Steve

Indeed. Congrats on the successful resolution of the problem.

:seasix:

Live well,

SJW

I love a happy ending.

Probably some kind of animal tissue.

Steve

An earlier post gave it away but it was oil from sperm whales..

So that’s whale oil?

Take care,
Steve

Sorry to the whale, and not a product being produced anymore, thank god, but that's what I was told it has in it....?:confused5:

Steve, I deleted that info and picture, so not to promote that product.:seasix: