Changing diff fluid. Do I need friction modifier
 

I thought I had a posi because when I was checking to see if my 4x4 worked, I pealed out in some gravel, and both rear tires spun. But now that I have it on jack stands, I believe its limited slip, because when I turn the right side wheel, the left side goes in the opposet direction. If I turn left side, only it turns. Thats limited slip,,,,right??

So to the point. Do I need to add anything to the rear diff,,such as friction modifier. Thanks

RE: Changing diff fluid. Do I need friction modifier
 

No. The G80 diff requires no special additive.

RE: Changing diff fluid. Do I need friction modifier
 

I just checked. I have a GU6. That's limited slip,,right?? Do I need aditive for that. Thanks

RE: Changing diff fluid. Do I need friction modifier
 

Yeah, what Jon said. GU6 means your axle ratio is 3.42:1

RE: Changing diff fluid. Do I need friction modifier
 

gu6 is 3.42 gears not limited slip

RE: Changing diff fluid. Do I need friction modifier
 

The GU6 was the only G code, so I assumed that meant limited slip,,not a G80 posi. So whats that mean with no other G code.

RE: Changing diff fluid. Do I need friction modifier
 

no other g code just means that u have a standard rear end nothing special. u just spun both on loose gravel.

RE: Changing diff fluid. Do I need friction modifier
 

The G80 code indicates a Gov-Loc differential which is a lockingdifferential .Locking differentials do not have clutches and therefore do not need friction modifiers. The old style friction modifiers weremade ofwhale oil butJane "Save The Whales"Fonda put a stop to that . Without whale oil modifiers, theautomobile manufacturersintroducedthe quiet and smooth locking differentials that did not haveclutches. TheGov-Loc locking differentialsare not like the old Detroit Lockers that had theclick, snap, bang and pop when you droveon anything but a straight road. The Gov-Loclockers engage when one rear wheel turns faster than 100 revs than the other wheel and it will disengage afer you reach 20 MPH. Above 20 MPH, it becomes a standard differential. That preventsexcessive tire wear and is much safer than the oldDetroit Locker that was optional with some high performance cars of the 1960s' .

UseSAE 80W-85W-90 gear oil, API service GL-5. Recently I changed the lube in my G80 differential and installed2-quarts of NAPA Premimum Gear Oil (Valvoline).

RE: Changing diff fluid. Do I need friction modifier
 

So unless I missed something,,,I still don't know if I need any additive or not.

RE: Changing diff fluid. Do I need friction modifier
 

I'd say you missed something.

twice.