greetings all,

i am new to this c-5 forum as i have a c-4. i am asking this here for a friend whom drives a 2003. the car is stock with 17,500 miles on it. the symptoms are that when the driver makes left hand turns, there is a growling grinding noise from the rear end. the car is a daily driver and is babied incredibly.

the car was taken into the shop about a year ago with a differential leak and similar growling noise, with the shop replacing the rear end as i am told. just this week, the car was making the exact same noise and the shops solution was telling my friend that the muffler was replace because it was "loose" (sounds like a snow job to me!).

prior to her getting the car back today, they had said that they changed the differential oil (which was already running a synthetic and changed out about a year ago) and they contend that that was the problem. they had stated that the c-5's were notorious for differential problems.

like i said, it's a daily driver with no racing or anything like that. i am of the belief that the differential oil should last somewhere between 50k and 100k with normal use.

my belief is that since it the problem occurs with "left hand turns" only, i would suspect that it would be a rear wheel bearing "loading up" or a minimal belief of one of the u-joint taking a "dump". this is not tp preclude the differential being bad which the shop won't admit and may be trying to cover up with a heavier gear oil.

you c-5 guys, what do you think and do ya have any comments pertaining to what you may think it is or other suggestions relevant to the problem.............thanks!!

 

other than minor drip-leaks... I don't know about the carrier (diff) being "notorious" for any other problems on a stock car.

If this is a stock car, then have the fluid replaced with genuine GM synthetic fluid; along with a bottle of limited slip friction modifier (GM brand as well). This fulid works well for stock setups. Then after this change of fluid (and added bottle of friction modifier fluid), have your friend do some figure 8's in a big parkling lot - with the help of a spotter (no need to run into lamp posts ).

If the noise doesn't completely go away in a couple of weeks, then it's time to have the carrier (differential) looked at more closely.

 

two quarts of GM synthetic rear axle fluid (GM # 89021677), and a bottle of limited-slip additive (GM # 1052358).

 

I also would suggest a lube change with the GM additive as I've read many articles where this works.
If that fails have DTE install a rebuilt differential with 4.10 gears and ZOOM, ZOOM!

 

Yes, what you've described is a classic case of needing to have the Diff serviced. The anti-slip lube is not only a good idea, it's a GM requirement! Check your owners manual under fluids. This is a pretty simple procedure if you have a jack and a pair of jack stands, except that draining the old fluid is really stinky!

I had a '98 TransAm that made the same noise and I had the dealer do the service. Don't know what the GM recomended period is to do this, but I'd recommend every 30K miles or sooner. If this doesn't solve the grinding problem, your next step is to have the wheel bearings inspected - but just a guess.