Jackfit

Hello out there in Corvette land...

Time for maintenance on my car after putting 60,000 miles on it in the last 4 years.

About 250-300 k miles on car and rear end.

Did not take good car of it for 40 years, but have drained and cleaned and new fluids etc . preparing it for my travels.

I have been having vibrations and did replace u joints on half-shaft last month on pass. side.

Noticed some vibration....could it be the mechanic who did the work (me)...

So car really make a noise (pop) after a few weeks of driving...noticed a really thump ,

Tonight have car up on jacks, turn wheels and hear crackling sound as I rotate wheel. Can't be good ...

I drain rear and as I look at fluid from my hose it looks like gray metal fake in the gear oil

So...what 's the story....I was going to fill it and see what happens...but will wait for your opinions..

Jack

Nowhere Man

If you see metal in the oil I would not waist your time putting new oil in it. Sounds like its time to pull the rear

Dale002

Make sure it's metal by sticking a magnet in the oil.

LT1driver

I agree, make sure it is indeed metal before removing. good luck.

DansYellow66

More things wearing in the Corvette rear to create debris than most GM differentials because of the yokes. Draining and refilling might be OK for a garage queen, sunday driver. But considering how much you drive your car, I would be thinking about having it rebuilt.

Roger Walling

There is something worse than oily metal flakes; DRY metal flakes.

I had a Eldorodo once and I would check the trans axel for fluid regulary.
(I thought it was a transaxel because they are so close)
It turns out that there was not a drop of oil in the diferencial and the pinion wore out completly so that it dident engage with the ring.
No noise, no clunking, just no go.

Jackfit

I was out to the garage this morning after reading your post. What I am seeing in the oil is very very very fine silver like (metal flake) in appearance. All are the same tiny tiny size.

I stuck my magnet in the oil and all of it ran off. No sticking to magnet.

I will refill the rear with gear oil and posi additive and see what happens.

I still am hearing the click as I spin the wheel. I will keep you posted later today when test the car out.

Jack

Plasticman

Where do you have the rear supported? On a C2 or C3, you cannot let the rear wheels just hang down, when the car is supported on the frame, and then spin the rear wheels (due to too much "angle"). The rear axle U joints will be in a binding situation as you rotate the rear wheels (some more than others).

The flakes sound like posi friction plate material. If the posi is still working properly, not a concern.

Plasticman

Mako6

Agree,,, fairly normal (micro metalic debris in the gear oil). I would give the (outside) wheel bearings a real good look though. The growling (crackling) you describe would leave me concerned about their condition.

Mak

ifitgoesfast

Agree with Mako re: rear wheel bearings. Before mine failed, it squeaked once in a while, then began clicking, then growling. You might have two unrelated issues. The easy one and I'd say more dangerous is the rear wheel bearing. Definitely, as Mako posted, check that out first before driving anymore (could take out entire rear fender). Good luck.

Jackfit

Put in new complete trailing arms, bushings , bearings ect in 2004, about 60, 000 , Miles ago ,I will check out wheel movement later today

Jack

Bluestripe67

Plasticman (John) has a good point about leveling up and then rotating. Dennis

Dale002

The magnet in the oil always works for most metals. I would not worry about it too much as it sounds as it's normal. Keep in mind that all machines that operates metal to metal will make some metal! The oils keeps it cool and help it last much longer but doesn't keep it from making metal or eventually wearing. Put the right amount of oil and anti slip additives then see if the issues go away. If not troubleshoot accordingly.

Also as other have said. if it's jacked up and the angles are off it will make a terrible sound when you turn the rear wheels.

Jackfit

Hi, thanks for the replies. I put new fluids in , took it for a ride and it is still vibrating.. Unfortunately, it does not feel like it is the rear, but a rear bearing thump or out of sync / failing u-joint....I tried to move the wheel side to side when up and could not feel any give , I once had the wheel come off from a failed rear bearing , so I don't want that to happen...

U-joints are new , just put in a few weeks ago on the side that feels off.


What is a simple check I can do ?

Thanks

Jack

1955 copper

If your rear is a POSI the clutches are slipping making cracking sound ( turning makes more sound ) Change to better POSI oil . ???

Dale002

I would make sure this was done with high quality anti slip additive. If it feels like one wheel is breaking loose while stop at a light or stop sign or when your are stopped using foot brake, It's a lack of anti slip additive. I would also checked all the U joints , driveshaft, half shafts for damage or missing weight. Check rear axel housing rubber mounts as well as the transmission rear mount for damage. I would also check the forward bushings on the rear trailing arms for wear. Even thou you said they were replaced, you never know. Make sure the shims are still there and that there is no play at that point.

Jackfit

Hi , all u-joints are new or less then 2-3 years old. All look good no play. The knock or vibration seems to only take place when Under load , not when coasting ??? All shims in place , strut rod bushings are poor, 46 years old. But no problem with tire wear.

Jack

ifitgoesfast

I forget what it's called, but have you checked the rear differential rubber mount (that goes under the differential)? When those fail, you get a little slop and movement, enough to make noises you describe when throttle is applied.

ifitgoesfast

Check rubber mounts marked B and C
http://content.mamotorworks.com/img300/fr1433.jpg

Pilot Dan

With that kind of mileage, I think it's time to service the rear. I would not be surprised if your stub axles have excessive play and clutches are worn. In mine, the center pin was worn and allowed side play in the axles. Gary Ramadei did a superb job on the rebuild. I'd suggest you give him a call and discuss your problem. Best move you could make. Pilot Dan