DennisC5

I have developed a strange clunk in the right rear of my 66 Vert. It's a stock 327 4 speed. When I first start the car and drive it, it's fine, no noise. Seems like after I have driven the car for 30-45 minutes stop and start, there feels like something is clunking in the right rear. Almost feels like a tooth off a gear in the rear end. Let it sit over night, clunk is gone. It comes back after it gets hot. Is this the rear end dope? Not sure if it's a posi-traction rear end. Feels almost like the rear end is shifting. Can anyone tell me where to start looking? Had it on a rack 2 times nothing appears loose? Thanks for any help..

66jack

Sounds like you have a bearing going south/out...

DennisC5

Are you talking about the bearing in the trailing arm or the rear end?
Thanks

anyChevy

Jack up the rear end, if both rear wheels rotate in the same direction (by hand) its a posi.
If nothing external is loose, it could be the posi clutches binding when hot.
A change of fluid and a bottle of additive usually fixes it.

jprop

I would guess a U-joint. A bad U-joint is a very common problem that makes a "clunk" in the rear. The good news is that it is inexpensive and easy to fix.

outlaw67

All of the above , just as a precaution check every thing , I have found if it's the diff , it will clunk only at slow tight turns , check all universals for movement , make sure the wheels are supported and not hanging, then suspend the rear wheels , grab the tyre at 12 o'clock and 6 o'clock and rock to check wheel bearing movement in the carrier , there should not be hardly any , also check front trailing arm mounts for movement and that the shims are all in place and shock mounts , If you do not know when the wheel bearings were last done I would pull them apart anyway ,you can chew an axel on these real easy if a bearing starts to go, have fun

magicv8

After the car starts the noise, walk up to the noisy wheel, grab it at the top with both hands and rock it in and out to see if the spindle has play and makes noise.

67vetteal

I would not drive the car until problem is diagnosed. These cars can go on Fire if it's a Wheel Bearing. BTW, I always have a fresh Fire Extinguisher in our Vette. Al W.
I just found this in another Tragic Post about the Duntov Group losing their Trailer/Hauler and Four cars!!
I don't know all the details, but somewhere between their shop in Texas, and Watkins Glen NY, Duntov Motors' trailer caught fire. The fire started in either a brake or wheel bearing, in one of the trailer's wheels.

DennisC5

Thanks for all of your responses. Looks like I have a multitude of things to check. I will give each one a go and see if I can pinpoint the problem. I really appreciate everyone's advice.
Thanks!!
Dennis

garyguinn

I had a similar problem on my 65 coupe.
Pinion gear was loose.....I was lucky, no damage....but did have to
drop the whole rear end to fix the problem...
Good luck

Gary

Martyt

Glad I read this thread--67Vetteal reminded of something I keep forgetting to do---fire extinguisher !!!

DennisC5

If the wheel bearing was bad, it should make a noise all the time? Correct? Just drove the car again, really slow, listening. no noise. drove it around about 5 blocks, no noise. If a wheel bearing was bad it should not fix it's self by letting it cool. A bearing is either bad or it's not. Car reacts perfectly going around corners and stop and go driving. Only when it gets hot does this start happening. I'm going to start with changing the rear end fluid and add 2 bottles of GM positraction additive. Will keep everyone posted.
Thanks again!

Vet65te

Is this 'clunk' just a single isolated sound or a series of 'clunks' all together? There's been lots of good suggestions on what could be causing the problem but let me add one more. If that sound seems to be a single sound such as pulling away from a stop or after just shifting gears, check out the pinion snubber bushings. The lower bushing is pretty easy to check when the car is up on stands or on a rack but the upper bushing isn't so you'll have to reach up and feel for it. If one of those bushings is wasted, it could be causing that sound you're hearing.
Mike T.

ghostrider20

If it's the rear end, go to a paved parking lot and do a tight radius turn when the problem presents. If it's the rear end, you will hear a binding, popping, and grinding sound. A change of lube and 2 bottles of additive may do the trick.

A bad u-joint will be present all the time and you could check them by loading, and unloading the drive train (forward, reverse, etc)

The trailing arms bearings can have many symptoms. Mine started as a chirping Parakeet, then to a constant Chirp, then clunk and grinding.

austbrad

I had the same clunking sound on my 66. Turned out to be loose bolts holding the differential onto the cross member. I would not hear any noise under light acceleration, but when I accelerated abit harder, the noise returned.

67vetteal

Dennis, Get yourself an IR Device to measure Temperatures. Drive the car for a few miles. Take the IR and measure the Wheel Hubs, Universals etc.. Something might show up. Be proactive on this situation. Lazy gets expensive. Al W.

DennisC5

Finally figured it out. The car had been sitting for about 3 years. Started driving it, after working on it off and on during that time. Evidently, the rear end gear oil had dried up in the posi clutches. I pumped out the old, pumped in the new, with 2 bottles of GM additive. Drove it 2 solid hours making figure 8's during the drive. Good News! No more clunking! Hooray!!
I have driven it several times over the weekend and the problem hasn't returned. Thanks to all of you that made suggestions. I tried the simplest way first, thank goodness, it worked.
Thank goodness too for this great forum!