Rear diff fluid & additive
Thread Starter
Pro
Joined: Nov 2003
Posts: 692
Likes: 1
From: Peabody Ma.
Rear diff fluid & additive
How much gear fluid and additive should I install in the rear diff. Also what brand is best? I just had my 3:55 installed, and well be installing hopefully next week sometime. Waiting on one more part. I post some pics of the install. TIA
Drifting
Joined: Oct 2007
Posts: 1,458
Likes: 1
From: Collinsville MS
St. Jude Donor '08
I used Lucas 85-140 gear oil and two bottles of GM posi additive in mine when I changed it. Since yours is new you will probably need only the one bottle of pos additive. After you change it, go to a nearby parking lot and make a series of slow figure 8's to get it all mixed and lubed up.
Pro
Joined: Oct 2004
Posts: 624
Likes: 24
From: Shoreline WA
rear differential "oil" change
I'm also getting ready to change this. Picked up the posi-additive yesterday at a Chevy dealership but haven't got the gear lube yet. LUCAS apparently has a synthetic, and while recommended I'm still looking for an "AC DELCO" product for the regular gear lube. "Schucks Auto Parts" doesn't carry it but I'm still looking. Maybe it doesn't matter too much? Others have mentioned that it's an easy procedure, but I only want to do it once plus there's no rush for me. 37 years since it's St. Louis birthday!
Let us know what you finally end up using.
Let us know what you finally end up using.
Melting Slicks
Joined: Mar 2005
Posts: 2,838
Likes: 10
From: Austin TX
Eaton "Strongly Recommends" the use of conventional lube with their posi units (installed on our Vetts).. Synthetics are too slippery and will decrease the effectiveness of your posi. This is from the Eaton page:
"What kind of oil should I use? Can I use synthetics? Do I need a friction additive/modifier?
Eaton Posi units perform best when using GL4 (or better) mineral/petroleum based gear oil. A four ounce bottle of friction additive/modifier is also necessary for optimum performance".
More here:
http://www.eaton.com/EatonCom/Produc.../FAQ/index.htm
"What kind of oil should I use? Can I use synthetics? Do I need a friction additive/modifier?
Eaton Posi units perform best when using GL4 (or better) mineral/petroleum based gear oil. A four ounce bottle of friction additive/modifier is also necessary for optimum performance".
More here:
http://www.eaton.com/EatonCom/Produc.../FAQ/index.htm
Race Director
Joined: Jun 2005
Posts: 10,189
Likes: 206
2018 Corvette of Year Finalist
2017 C3 of Year
GM posi lube along with whale oil (old school) if you can find it or today's synthetic additive. My diff. took 2 1/2 bottles plus the additive. At the dealer I paid 44.00 for the materials. Also to remove the plug I used an 5/8" 8 point socket. I was told to remove all the old fluid. Good luck WB
