F-Body Europe

Hi,

when driving at extremly low speeds (between 25 and 40 kph) and at very low load (that means slighlty descelerating or even slightly braking) I can hear a sound from the rear: Clac clac clac clac clac, I would say about 5 clacs per second or so, maybe less.

What is this? The differential? If yes: is this a problem or will it develope into one?

And by the way: Driving with constant speed at 80 to 90 kph or gently accelerating at this speed I hear another sound from the same location, a sort of whine.

Any experiences that could be shared?

It sounds to me like either you have no fluid, which is extremely bad, or you have a very low level of fluid. I would not drive it until you check it. That is without question. If you continue to drive it, it might lock up like mine did, and then you will be in BIG trouble.

Horst:

I don't have the "claclaclac" sound you describe but I also have the whine -- from day 1, not getting any worse or better. I would not worry about the whine if it doesn't change over the time but as Jack said, check the diff fluid (level).

Ben

I think the whine is the beginning of the problem. If you are low on fluid, drain it, and then replace it, making sure that you add some limited slip additive! That helps with some of the whine.

I replaced my fluid last year and added the limited slip additive and the whine didn't change a bit. But I don't know what diff type Horst has... I have the Zexel Torsen diff without clutches so it doesn't necessarily need the lim.slip.a. contrary to the Auburn diff.

Ben

I will check the fluid level tomorrow. Although I didn´t recognize any leaks and the car (that I purchesed 2nd hand from a dealer) has records of all scheduled maintanances at a Chevrolet delaership - I suppose they must have checked and changed all fluids according to the maintenance schedule.

Anyway - I don´t even know which differential I have got: The previous owner has removed the sticker with the RPO codes from the door. All I know is that I have got a 2000 V6 modell.

Another thought: If not the differential, could it be either the wheel bearings or the drive shaft? My car has almost 90,000 km on the clock.

The German maintenance schedule says "Change rear diff fluid after 1st inspection and never change it again". So better change it even if it's at full level.

Ben

[quote="BenZ28"]The German maintenance schedule says "Change rear diff fluid after 1st inspection and never change it again". So better change it even if it's at full level.

Ben[/quote]

Strange. The German maintenance schedule of my car says "Change rear diff fluid every 15 000 km".

Really? I was referring to the dealer's schedule. Have a copy of it at home, and there it says to only change once (what is BS I think).

Ben

I changed the rear diffrential oil also at first service with 15000 KM and then never as stated on GM/Opel Dello's schedule.

Hello Horst,
I got the same clac clac at very low speeds as you. Its has been there for the last 20000km (the car now has 41000km on the clock). You are right: The maintenance says "Change diff fluid every 15000km). But the GM dealers never changed! I have the bills from the first owner.
Now I am with a free garage. They changed the diff fluid, added the Lim Diff Additive but the clac clac is still there and now it is rather amuzing me!
no need to worry.

Gunnar

BTW: The whine I got only at the gas station, when I look into my wallet.

Gunnar you crack me up with that one

Gunnar you crack me up with that one

Today I had the car checked.

The noise seems in fact to be coming from the differential. Standing below the car it really sounds bad. Driving in the car it still is only detectable when I am actually listening.

Anyway. My mechanic said it´s likely to be the bearings within the differential and as a secondary damage the cogwheels, hence the whine that is already slightly getting worse.

He said it won´t get better and recomends to change the differential as long as I have got still warranty on the car.

Let´s hope that this will be covered as long as it is still working.


UPDATE: Sept 7th 2004:

Well - I had it checked again at a Chevrolet garage during the regular maintenance. They changed the differential fluid and said it should be ok now.

It wasn´t. So I went back yesterday, and the mechanic had the car run in D with the rear wheels up and checked evereything with the stethoscope. The result was surprising: Noises where not detectable within the differential or rear axle bearings, but in the centre bearing of the drive shaft! That reminds me of an old service bulletin I have read somewhere in the web without bookmarking it, stating that the V6 Camaros after 1999 or so had problems with vibrations in the drive shaft that eventually could cause leaks at the transmission seal.

After I talked about that to the mechanic, he said that he had actually repaired some damages of that kind, in one case the flange at the transmission was actually torn off!

So - do I just change that bearing now? Or can I upgrade to the LS1 aluminum driveshaft? My mechanic is worried that it might not fit.

P.S.: Has anyone actually done the upgrade to the LS1 driveshaft?

good questions there -- does the LS1 DS fit, and would it be advisable to change it out? If so, does anybody happen to have an extra DS?

All driveshafts are interchangeable (as far as i know from 82 and up, correct me if i´m wrong).

I replaced my 2-piece steel unit with a aluminium one out of Rich´s TransAm, no problems, just a bit more power due to less rotating mass, hehe.

I just can offer again even two 2-piece steel driveshafts...
(I got all stock V6 parts, like exhaust and suspension things laying around, most of them twice - we modded RT1s car in my workshop )

Well - here a little update on the clac clac clac issue:

Since I had an unfriendly encounter with a barb wire fence I had to put my car into the workshop anyway to get a new fender, bumper and paint.

I chose a time when I had to go abroad for a week and told the guys at the workshop to take care of the clac clac clac, too.

Well - as I wrote earlier even with a stethoscope they couldn´t find anything wrong with the differential, but they located an unusal noise in the centre bearing of the drive shaft. As it turnd out, it could only be changed together with a new drive shaft. On my question whether they could put in an aluminum drive shaft, they said the flanches would be different and the warranty insurance would only pay for the original part anyway.

But now, about a week after the replacement, the noise is coming back. Not as loud as before, but clearly detectable at low speeds of about 30 to 35 kph when descelerating. And it increases at curves to the left, it decreases at turns to the right.

So - did I possibly have a drive shaft changed that was still ok???

Thanx

The truth is in the differential, Pull the service cover and check the differential pinions and side case gears.

As for the sound coming from the center carrier bearing , Ive seen em misdiagnosed before , Gotta remember the drive lines are hollow so Noise transmission is a definite possibilty from the differential to the carrier bearing. Won't know till you take it apart.

Listen to Roy- he knows his 5hit!