Differential fluid
Thread Starter
Melting Slicks
Joined: May 2000
Posts: 2,498
Likes: 4
From: Brentwood TN
Differential fluid
Don't want to and am not trying to start a p..sing contest about rear end lubes. Just need to know if 75W90 SYNTHETIC is okay for a '98 rear end. There are stories about paper seals and synthetic Dexron III being incompatible, but is synthetic lube, regardless of brand, okay in the '98? Again, don't care about brands. Just synthetic vs. dino.
Charlie
Charlie
Team Owner
Joined: Mar 1999
Posts: 22,025
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From: At the beach in little Rhody
I used Amsoil in my stock rear differential and last change it was still "blue", the color it went in. Now I use Redline as required by DTE since I am running one of their units.
Thread Starter
Melting Slicks
Joined: May 2000
Posts: 2,498
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From: Brentwood TN
Premium Supporting Vendor
Joined: Aug 2001
Posts: 5,364
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From: King George VA
Charlie,
I believe that the owner's manual requires a synthetic 75w90 in the differential (I know my 02 owner's manual does). I don't remember reading any posts about blocking rings in the diff, those are in the manual transmission.
I believe that the owner's manual requires a synthetic 75w90 in the differential (I know my 02 owner's manual does). I don't remember reading any posts about blocking rings in the diff, those are in the manual transmission.
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Instructor
Joined: Oct 2007
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Don't want to and am not trying to start a p..sing contest about rear end lubes. Just need to know if 75W90 SYNTHETIC is okay for a '98 rear end. There are stories about paper seals and synthetic Dexron III being incompatible, but is synthetic lube, regardless of brand, okay in the '98? Again, don't care about brands. Just synthetic vs. dino.
Charlie
Charlie
also don't forget to add the
Limited Slip lub Additive Part No.1052358
Last edited by q8_c5; Jan 16, 2008 at 03:27 AM.
Team Owner
Joined: Mar 1999
Posts: 22,025
Likes: 192
From: At the beach in little Rhody
Both Amsoil and Redline are synthetic and unless you get the 75W-90NS Redline, both have the limited slip additive in the fluid already such that adding more could result in loss of limited slip capability. I don't recommend using the "NS" Redline, its the same fluid but will require you to also get the Redline limited slip additive and put that in as well.
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Pro
Joined: Dec 2004
Posts: 670
Likes: 28
From: Mitchell SD
I've put synthetic differential lube in six of my cars with limited slip differentials over the years without the limited slip additive and they all worked great. I think the synthetic lube is slippery enough without the additive.
Instructor
Joined: Oct 2007
Posts: 151
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with u but u can say its like an extra safe,,maybe u didn't have problem before but its not mean that its can't happen in the future u can't tell..i've had my c5 for about 3 years now every thing was ok until i heared thats agly diff voice last mounth and i believe thats happened with many people out there..i can garantee that GM didn't make it with out a reason..for me i don't want to pay some more thousends on diff again,, be safeier for 5$
Last edited by q8_c5; Jan 17, 2008 at 02:51 AM.
Pro
Joined: Dec 2004
Posts: 670
Likes: 28
From: Mitchell SD
with u but u can say its like an extra safe,,maybe u didn't have problem before but its not mean that its can't happen in the future u can't tell..i've had my c5 for about 3 years now every thing was ok until i heared thats agly diff voice last mounth and i believe thats happened with many people out there..i can garantee that GM didn't make it with out a reason..for me i don't want to pay some more thousends on diff again,, be safeier for 5$
Thread Starter
Melting Slicks
Joined: May 2000
Posts: 2,498
Likes: 4
From: Brentwood TN
Thread Starter
Melting Slicks
Joined: May 2000
Posts: 2,498
Likes: 4
From: Brentwood TN
Team Owner
Joined: Mar 1999
Posts: 22,025
Likes: 192
From: At the beach in little Rhody
I now run a DTE rear differential and DTE requires a lot more additive than what Redline has in it. But this is due to the heavy clutch pack they run and what they have found is required for optimal limited slip capability.
I would be careful about putting in too much additive on initial fill.
Racer
Joined: Apr 2007
Posts: 380
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From: Long Island New York
I think I may have added to much additive yesterday when I changed my diff fluid and it feels like I have lost power. Can I fix this by just draining and refilling or can using to much additive cause perm. Damage?
Premium Supporting Vendor
Joined: Aug 2001
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From: King George VA
That said, I'm not sure how too much additive could make it feel like you have lost power unless you are getting lots of wheel spin. All the additive does is help the diff clutch plates slide when there is differential motion between the two rear tires (like when in a very tight turn) vice stick and release, stick and release (e.g. chatter). If the fluid has too much additive, all that will happen is that the clutch plates will slip more than design and your limited slip diff will be less limited slip. The limited slip diff is only designed to transfer about 75 ft-lbs of torque to the wheel with grip. Too much additive may lower that number, but I doubt by enough for you to really notice by the seat of your pants... and that only if you are getting wheel spin from one tire.
Did you change anything else?
Tech Contributor
Joined: Jan 2007
Posts: 19,465
Likes: 1,167
From: Dyer, IN
If it starts chattering when you turn a corner you can always add the friction modifier later. It really shouldn't hurt anything, chatter just tells you the friction discs are not slipping enough when you turn a corner. I would rather have a good tight posi that puts power to both wheels when I take off.
The service manual states:
# Fill the differential with fluid.
* Use synthetic axle lubricant GM P/N 12378261 or equivalent meeting GM specification 9986115 to approximately 1.6 L (1.69 qt).
* Use limited-slip differential lubricant additive GM P/N 1052358 or equivalent to approximately 118 ml (4.0 oz).
# Check the fluid level to ensure it is even with the bottom of the fill plug hole to no lower than 6 mm (0.25 in) below the opening.
The additive is a whopping $9.83. So what's the problem?