I am looking at a 2000 C5 coupe, auto. The guy selling brought it over, when I executed tight circle 8s, there was a grinding sound from the rear end. I was thinking perhaps a wheel bearing or the diff. The guy said he took it to a dealership after he left and that the problem was axle fluid/lube breakdown.

Anyone have any experience with this or can otherwise comment ? Thanks

 

I have delt with this before. When I changed the fluid the sound from my rear end went away. just recently started hearing it again. Gonna chance fluid soon. When I use Royal Purple gear oil the sound was gone for about 40k miles. When I use gear oil from dealer i had to add an extra limited slip additive too and noise came back way too soon. Dump another bottle of additive and repeat every few months. It got old real quick. Royal Purple has additive mixed in. My noise wasn't a grinding but more a grunting at low speed tight turns. Hope this helps you.

 

YES!! Change out the differential gear oil. Make sure that you use a 75-90 GL5 Gear lube as it will have the limited slip additive already in the lube.

If you change out the lube and it still makes noise on tight turns, you may need to add some additional limited slip additive.

The additive allows the limited slip clutches in the differential to slip. DO NOT add too much.

 

Is it also possible the differential clutch plates need to be replaced, or will the oil change most likely solve the issue ? Car has 64k on it.

 

Here’s the deal. ALL C5s have the same rearend design. There are special springs in each clutch pack that have a tendency to BREAK.

IF,, that spring breaks, the clutches no longer have the correct preload and fail to function as a limited slip unit. YES, they can cause noise and abnormal wear.

Have the garage jack up ONE rear wheel, the other rear wheel still on the ground and put the Trans in Neutral. Try to rotate the wheel that is off the ground.


If the clutches are operating correctly, it will be very difficult to rotate that wheel (cause the clutches to slip) New clutches have over 100 ft/lbs break away torque

If the springs are broken, it will be pretty easy to rotate that wheel.

Then check the opposite wheel the same way!

While the wheel is off the ground, grab the wheel at the 12-6 O clock and then 9-3 O clock positions and push and pull to see if you have any slop in the rear wheel bearings.

You should have very little or NO slop in either wheel bearing.

Here is a picture of a good and a broken Belleview spring (BAD on the RIGHT, GOOD spring on the LEFT!






Here a post that shows you the inside of the rearend and where the springs are:



- C5, ragtopws6 , Upgrading your C5 rear with C6 Z06 guts, : http://forums.corvetteforum.com/c5-g...-z06-guts.html
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- C5, Its_Go_Time, Output Shaft Install - Left and Right: http://forums.corvetteforum.com/c5-t...post1573407966

- C5 Differential Seal replacement: http://forums.corvetteforum.com/c5-g...on-photos.html
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Just use the GM stuff with the proper amount of LS additive in it; P/N is 88862624 or 10-4034. As others have said, too much LS is just as bad as too little. I've had great luck with this stuff, a little less than two quarts.

 

Had the grinding noise on our C6, even with the Royal Purple 'has lsd additive built in' gear oil.

2 ounces of the ACDelco additive did the trick.