Information on changing rear fluid

[Rookie Vette owner]

Is there a set procedure on changing the rear fluid in a C5? Do I need to flush under normal conditions, or just drain and replace quantities of oil and friction modifier to spec (1.6 qt & 4 oz). Thanks again for all your help CAC!!!

 

[99WhiteC5Coupe]

Is there a set procedure on changing the rear fluid in a C5? Do I need to flush under normal conditions, or just drain and replace quantities of oil and friction modifier to spec (1.6 qt & 4 oz). Thanks again for all your help CAC!!!

I did mine last Fall (1999 C5 coupe). I removed the drain plug (10 mm square drive for a 3/8 ratchet) and let the fluid drain overnight. The drain plug is underneath the differential carrier, so all of the fluid will drain.

Then I added the GM fluid including the 4 oz. of modifier and drove the car about 500 miles in the next month or so.

Then, following a several hundred mile highway drive, the rear differential began chattering on turns from a stop (such as turning at a stop light).

I took it to a Chevrolet dealer who said there was a TSB that instructed the dealer to add another 4 oz. of the GM friction modifier, then drive the car in 8-10 "figure 8's" in the parking lot to work the new additive into the plates.

That solved the chattering.

Good luck.

 

[Rookie Vette owner]

That is exactly what I am experiencing! Only thing different is when I took it to the dealer, he said I needed a fluid change, until I reminded him that he just did it about 3 months ago. He did some more checking (twiddled his thumbs) called me back and said I needed a $1200 clutch pack change. He did this without even opening the diff!! I declined and the fact that he didn't open it was apparent when I picked it up and he didn't even charge for the inspection/cover removal. I have since found that they also over charged me for the last fluid change, in that they charged for 3 qts of oil and 2 bottles of friction modifier. I think I'll be adding the extra modifier over the weekend! Thanks again for the info and glad you got it straightened out.

 

[LittleRedFlatBack]

I did mine last Fall (1999 C5 coupe). I removed the drain plug (10 mm square drive for a 3/8 ratchet) and let the fluid drain overnight. The drain plug is underneath the differential carrier, so all of the fluid will drain.

Then I added the GM fluid including the 4 oz. of modifier and drove the car about 500 miles in the next month or so.

Then, following a several hundred mile highway drive, the rear differential began chattering on turns from a stop (such as turning at a stop light).

I took it to a Chevrolet dealer who said there was a TSB that instructed the dealer to add another 4 oz. of the GM friction modifier, then drive the car in 8-10 "figure 8's" in the parking lot to work the new additive into the plates.

That solved the chattering.

Good luck.

Very good information. Thanks for sharing. Do you have any idea if this information holds true for a 2002 model also?

Dennis

 

[Dad]

Just went through this with my '05 C6 which was most likely built with left over C5 parts.

GM part number 88862624 (US-1 Quart) DEXRON® LS Gear Oil is the latest fluid for the C6 and I believe some C5s, modifier is in the formulation so none needs to be added.

Have your dealer look at TSB 07.04.20.002A.

While they're looking up that TSB have them look up TSB 07-04-95-001A May 29, 2008 (Replace wheel drive shaft nut) [2]. Published for the 2005-2009 Corvette. Can become very noisy if loose and they have changed the torque spec from 118 ft/lb (160 N-m) to 160 ft/lb (215 N-m) plus the addition of a thread locker (272 Loctite), 34 M/M socket required. Been there, done that, thought I'd lost a CV joint on the outside end of the wheel drive shaft. Nuts were warped and only contacted about 20/30% of the hub face. I'm going to make a threaded arbor to face them perpendicular to the axis of the thread if they come loose again.

Also Mobile 1 LS 75W90 gear lube is a replacement for the 88862624 GM lube and is half the price, $9 per quart, includes the friction modifier, sold at Advance Auto. Takes 30 minutes on a lift to change it with the use of a siphon gun, $10, and a 10 M/M hexagon allen wrench. Note the "LS" designation in both the gear lubes. Working fine so far, will certainly say something if it doesn't continue to do so.

 

[99WhiteC5Coupe]

Very good information. Thanks for sharing. Do you have any idea if this information holds true for a 2002 model also?

Dennis

The Chevrolet mechanic that added the fluid said it applied to "all C5's".

I was on vacation and out-of-state. The dealer was very honest and put my car ahead of others since I was traveling. I was afraid I needed a new differential.

I have since put about another 1,500 miles on the car and the differential has been absolutely quiet and smooth.

Good luck.