Rear diff already synthetic???
Thread Starter
Racer
Joined: Mar 2005
Posts: 288
Likes: 1
From: Maple Ridge British Columbia
Rear diff already synthetic???
I've been planning to replace my tranny and rear diff fluids as I now have 40K miles on the car. I've read here that you can replace the factory fluids with synthetic which will make the tranny smoother and help the rear diff run cooler. When I went to my owners manual to see what weight of rear diff fluid I needed, I was surprised to learn that it already has synthetic in it from the factory. Also, GM doesn't recommend that the rear diff fluid needs to be changed at all. Is this correct? Here's the recomended rear diff fluid replacement blurb from the manual.
SAE 75W-90 Synthetic Axle
Lubricant (GM Part No. 12378261
or equivalent) meeting GM
Specification 9986115. With a
complete drain and refill add
4 ounces (118 ml) of Limited-Slip
Axle Lubricant Additive (GM Part
No. 1052358 or equivalent) where
required. See “Rear Axle” in
the Index.
SAE 75W-90 Synthetic Axle
Lubricant (GM Part No. 12378261
or equivalent) meeting GM
Specification 9986115. With a
complete drain and refill add
4 ounces (118 ml) of Limited-Slip
Axle Lubricant Additive (GM Part
No. 1052358 or equivalent) where
required. See “Rear Axle” in
the Index.
Burning Brakes
Joined: Nov 2001
Posts: 1,163
Likes: 19
From: Not far from COTA
whether you change it or not depends on how long you will keep the car and how you use it (cruiser or track days)
most manufacturers say something like no maintenance required "under normal conditions" and then list what isn't normal
hot weather, lots of short trips and stuff like that is not normal
funny that other Chevy products do specify a change, like a pickup diff every 50k
most manufacturers say something like no maintenance required "under normal conditions" and then list what isn't normal
hot weather, lots of short trips and stuff like that is not normal
funny that other Chevy products do specify a change, like a pickup diff every 50k
Race Director
Joined: Nov 2005
Posts: 14,553
Likes: 1,549
From: Supporting the Corvette Community at Abel Chevrolet in Rio Vista, CA 707-374-6317 Ext.123
St. Jude Donor '08
Originally Posted by MacVette86
I've been planning to replace my tranny and rear diff fluids as I now have 40K miles on the car. I've read here that you can replace the factory fluids with synthetic which will make the tranny smoother and help the rear diff run cooler. When I went to my owners manual to see what weight of rear diff fluid I needed, I was surprised to learn that it already has synthetic in it from the factory. Also, GM doesn't recommend that the rear diff fluid needs to be changed at all. Is this correct? Here's the recomended rear diff fluid replacement blurb from the manual.
SAE 75W-90 Synthetic Axle
Lubricant (GM Part No. 12378261
or equivalent) meeting GM
Specification 9986115. With a
complete drain and refill add
4 ounces (118 ml) of Limited-Slip
Axle Lubricant Additive (GM Part
No. 1052358 or equivalent) where
required. See “Rear Axle” in
the Index.
SAE 75W-90 Synthetic Axle
Lubricant (GM Part No. 12378261
or equivalent) meeting GM
Specification 9986115. With a
complete drain and refill add
4 ounces (118 ml) of Limited-Slip
Axle Lubricant Additive (GM Part
No. 1052358 or equivalent) where
required. See “Rear Axle” in
the Index.
