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View Full Version : What kind of Diff Fluid you running?

Sarge
10-12-2005, 03:36 PM
Just changed mine out today...had Amsoil 75-140 w/ Amsoil friction modifier.
No problems at all......but I change the diff fluid every 2500 miles ....so this time around I put in Royal Purple 85-140 that comes with the FM already in it.....
just curious what my fellow GoatHeads have in theirs....
bad6as
10-12-2005, 06:47 PM
i dont think you need the 140w 75-90 is fine and i use amsoil in my 98z
Sarge
10-12-2005, 07:07 PM
We have different rear ends....sounds funny dont it:) But Fbodys and GTO's are way different man....I take 3 1/2 quarts of fluid...totally different set up....
Rob
10-12-2005, 07:35 PM
RP 85-140

No problems at all. No FM added and its been chatter free since I put it in about 2K miles ago.
Sarge
10-13-2005, 05:24 AM
RP 85-140

No problems at all. No FM added and its been chatter free since I put it in about 2K miles ago.
Hey Rob....I know often we do something and the "buttdyno" will confirm for us what our minds want it too....
but....I swear this thing hooks quicker....now how in the hell is that possible?
Mebbe the Amsoil didn't engage the slip diff as quickly...hell I dunno...just feels like it hooks instantly.....is very quiet back there:)
Rob
10-13-2005, 05:27 AM
Could be the FM additive? I know lots of people over use it and actually loose the posi because its too slick. I haven't used any FM in 15 years. I just use synthetic and change it every year and never have a problem.

So maybe the RP uses less FM than the Amsoil and since its not allowing as much slippage, you're using both wheels now.
Sarge
10-13-2005, 05:50 AM
Could be the FM additive? I know lots of people over use it and actually loose the posi because its too slick. I haven't used any FM in 15 years. I just use synthetic and change it every year and never have a problem.

So maybe the RP uses less FM than the Amsoil and since its not allowing as much slippage, you're using both wheels now.
Makes perfect sense....I put about 40 miles on her after the change...just cruising at 75MPH on the country roads......I nailed her at a stop sign in town....I swear she locked up and exploded....in the past she spun and hooked....but not this explosion....the FM comment you made is probably right as I think about it....the Amsoil came out like water.....
Rob
10-13-2005, 08:25 AM
Just have to realize that FM isn't needed at all. Its purely cosmetic. It could chatter until your teeth fall out, but it doesn't hurt the rear at all. All the FM does is cause it to slip so you don't feel it. If too much is used, you'll end up with 1 wheel burnouts.
Sarge
10-13-2005, 08:41 AM
Just have to realize that FM isn't needed at all. Its purely cosmetic. It could chatter until your teeth fall out, but it doesn't hurt the rear at all. All the FM does is cause it to slip so you don't feel it. If too much is used, you'll end up with 1 wheel burnouts.
You got me convinced......I just lit Main Street up:) Most definitely a difference for the good......
birddog0
10-13-2005, 09:44 AM
RUnning the same -- RP 85-140
GMinTheDriveway
10-14-2005, 12:20 PM
I'm running RP 75-140 with the Harrop cover. Runs great