Synthetic Diff Oil

LS2FAST · 10-10-2005, 08:02 PM

OK.... does anyone know anything about the ratio of POSI additives and Synthetic Differential Oil, specifically:

Increased or Decreaed Noise
Clunking Sound when accelerating Lightly
What happens if too much
What happens if too little

Please give me any input you may have regarding this.

Thanks in advance All who reply.

Subdriver · 10-11-2005, 12:08 AM

I believe that GM recommends adding 4oz of friction modifier to two quarts of diff fluid. I've read that if you don't add it the diff will "chatter" in tight turns.

AMSOIL Severe Gear Extreme Pressure Synthetic 75w140 comes with the friction modifier already in it. I use the 75w90 version of this in my Z06 on the track and have never experienced chatter, so I don't add the friction modifier.

LS2FAST · 10-12-2005, 08:08 PM

OK .... My car is in the shop as of this morning. "clunking" in the rear axle. Dealer said "syntehic will void your warranty if we find anything wrong". Has anyone else heard of this. And does anyone know the exact oil specifications for the differential recommended by Pontiac???

Xman · 10-12-2005, 09:26 PM

The GM rear diff oil is a synthetic. I've never heard that using synthetic will void warantee. I use Royal Purple. So does the GTO Race Car! Skip the mixing of friction modifier and use RP or Amsoil.

danrieke · 10-12-2005, 09:34 PM

Yes, the GM diff oil is synthetic. I'd contact GM about what the dealer said. Warranty work is like medical insurance... the dealer stands to make less $$ from GM doing warranty versus straight from your pocket.

Subdriver · 10-12-2005, 10:22 PM

Pulled this off another GTO thread:

"Straight out of the owners manual.

Rear Axle:
SAE 75W-140 GL-5 Synthetic Gear Oil (GM Part No. 89021809)."

I'd be really upset by what your dealer is telling you. First, I'd go straight to the service manager, then I'd call Pontiac Customer Service and report the dealership.

LS2FAST · 10-12-2005, 11:01 PM

OK.... should I take the car from the dealer tomorrow and just change the Oil myself and see if the problem is fixed, or should I fight this out with the dealer???

Anyone familiar with Magnusson Moss Act???

Groucho · 10-12-2005, 11:30 PM

Royal Purple needs no friction modifier...

GTODEALER · 10-13-2005, 09:25 AM

Quote:

Originally Posted by Subdriver

Pulled this off another GTO thread:

"Straight out of the owners manual.

Rear Axle:
SAE 75W-140 GL-5 Synthetic Gear Oil (GM Part No. 89021809)."

I'd be really upset by what your dealer is telling you. First, I'd go straight to the service manager, then I'd call Pontiac Customer Service and report the dealership.

.... that's b.s.!

dvillar · 10-13-2005, 09:36 AM

I'd definatley fight it out