diff fluid
Thread Starter
Racer
Joined: Aug 2004
Posts: 395
Likes: 1
From: Dartmouth Massachusetts
diff fluid
thinking of changing out my diff fluid for some aftermarket/synthetic to avoid going to the dealer (i have some chatter)
what brand/types have you used?
and what additive brand/type do i need?
how much of each?
i guess i need something to keep me occupied during the winter, going crazy
need some nice weather so i can start driving it again...
what brand/types have you used?
and what additive brand/type do i need?
how much of each?
i guess i need something to keep me occupied during the winter, going crazy
need some nice weather so i can start driving it again...
Instructor
Joined: Dec 2005
Posts: 135
Likes: 0
Member go to the dealer at NO COST!!!! There is a TSB on the issue and the remedy is to replace with a synthetic
. So, you are getting what you want and the dealer has to eat it. Might as well enjoy the molment, there won't be too many opportunities to take advantage of a dealership at there expense
. Especially if you own a vette. 
. So, you are getting what you want and the dealer has to eat it. Might as well enjoy the molment, there won't be too many opportunities to take advantage of a dealership at there expense . Especially if you own a vette.
Drifting
Joined: Jun 2005
Posts: 1,837
Likes: 4
I've been using the Mobil 1. With most of the synthetic fluids you have a choice of using additive or not. I think some of this is just personal preference - how tight do you want it to be?
Red Line recommends trying it without, then adding just enough to get it the way you want it. Makes sense to me.
Burning Brakes
Joined: Feb 2006
Posts: 926
Likes: 0
Member go to the dealer at NO COST!!!! There is a TSB on the issue and the remedy is to replace with a synthetic . So, you are getting what you want and the dealer has to eat it. Might as well enjoy the molment, there won't be too many opportunities to take advantage of a dealership at there expense . Especially if you own a vette.
. So, you are getting what you want and the dealer has to eat it. Might as well enjoy the molment, there won't be too many opportunities to take advantage of a dealership at there expense . Especially if you own a vette. 
Former Vendor
Joined: Aug 2005
Posts: 16,897
Likes: 412
From: Lewisville TX
St. Jude Donor '03-'04-'05-'06-'07-'08-'09-'10-'11-'12-'13
We use RedLine 75w90 in every HP build, and every single one of our World Challenge cars. One of the best oils on the market to date!
Team Owner
Joined: Oct 2004
Posts: 27,420
Likes: 64
From: San Clemente CA
Member go to the dealer at NO COST!!!! There is a TSB on the issue and the remedy is to replace with a synthetic . So, you are getting what you want and the dealer has to eat it. Might as well enjoy the molment, there won't be too many opportunities to take advantage of a dealership at there expense . Especially if you own a vette.
. So, you are getting what you want and the dealer has to eat it. Might as well enjoy the molment, there won't be too many opportunities to take advantage of a dealership at there expense . Especially if you own a vette.
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
150 hp to 1,250 hp: Every Corvette Generation Compared by the Specs That Matter
Joe Kucinski
8 Coolest Corvette Pace Cars (and Replicas) of All Time
Verdad Gallardo
Top 10 Corvette Engines RANKED by Peak Torque (70+ Years of Muscle!)
Joe Kucinski
Corvette ZR1X Will Be Pacing the Indy 500, And Could Probably Race, Too!
Verdad Gallardo
Top 10 Corvettes Coming to Mecum Indy 2026!
Brett Foote
Top 10 C9 Corvette MUST-HAVES to Fix These C8 Generation Flaws!
Michael S. Palmer
10 Revolutionary 'Corvette Firsts' Most People Don't Know
Joe Kucinski
5 Reasons to Upgrade to an LS6-Powered Corvette; 5 Reasons to Stay LT2
Michael S. Palmer
2027 Corvette vs The World: Every C8 vs Its Closest Competitor
Joe Kucinski
Safety Car
Joined: Jan 2006
Posts: 4,598
Likes: 78
From: Miami FL
2020 C6 of the Year Finalist - Unmodified
St. Jude Donor '08-'09-'10-'11-'12-'13-'14-'15-'16,'17,'18-'19-'20-'21-'22
The additive you want is GM part number 1052358 Limited Slip Differential Additive. At 1bout 1500 miles, both FXB3 and I drained our differentials (no symptoms in either one) and put in Mobil 1 synthetic 75W-90 axle lube plus the GM additive. Then we did a couple of dozen slow "figure 8's" in the parking lot to work the additive in between the clutch plates.
If you have symptoms, let the dealer do this for you at GM's expense.
.
If you have symptoms, let the dealer do this for you at GM's expense.
.
Thread Starter
Racer
Joined: Aug 2004
Posts: 395
Likes: 1
From: Dartmouth Massachusetts
Premium Supporting Vendor
Joined: Aug 2001
Posts: 5,364
Likes: 38
From: King George VA
Applicable AMSOIL diff fluid:
AMSOIL Severe Gear Extreme Pressure Synthetic 75w90
This fluid comes with the friction modifier in it and you should not need additional modifier, though AMSOIL does carry the product: AMSOIL Slip-Lock Differential Additive
The diff will take about 1.7 quarts so you'll need 2 quarts of whatever you decide to use.
AMSOIL Severe Gear Extreme Pressure Synthetic 75w90
This fluid comes with the friction modifier in it and you should not need additional modifier, though AMSOIL does carry the product: AMSOIL Slip-Lock Differential Additive
The diff will take about 1.7 quarts so you'll need 2 quarts of whatever you decide to use.
__________________
C66 Racing #66 NASA ST2, SCCA T2
AMSOIL Dealer (Forum Vendor)
AMSOIL Preferred Customer Program (Members buy at Wholesale - a savings of about 25%)
C66 Racing #66 NASA ST2, SCCA T2
AMSOIL Dealer (Forum Vendor)
AMSOIL Preferred Customer Program (Members buy at Wholesale - a savings of about 25%)
Le Mans Master
Joined: Oct 2006
Posts: 5,078
Likes: 19
From: Cumming, GA
Looking at using the Royal Purple Max Gear. I found some at a local shop here in GA and noticed it is a 75W 140 weight gear oil. I see Anthony from LG recommended the Redline which is a 75W 90 gear oil.
Whats the difference b/t the two gear weights?
Thanks.
Whats the difference b/t the two gear weights?
Thanks.
Premium Supporting Vendor
Joined: Aug 2001
Posts: 5,364
Likes: 38
From: King George VA
Essentially the viscosity. Using the AMSOIL's 75w90 and 75w140 viscosities as an example since I have those handy, the 75w90's viscosity at 100C (212F) is 16.4 and at 40C (100F) it is 108.79 cSt. The 75w140 is 25.7 at 100C and 185.6 at 40C. Essentially the 75w140 is heavier. This will provide better protection at elevated temps, but it will cause additional friction and heat at lower temps. GM recommends 75w90 in the stock diff and that's what I've been using on the track for years and have not had any diff failures other than a failed left axle seal which is a common C5 Z06 problem.