Guys - I swung by the Advance Auto Parts store yesterday and was checking out the rear diff oil and friction modifier.

The only friction modifier I saw available was this stuff called,

Posi-Trac
Limited Slip Gear Oil Additive.


It looked pretty generic. I guess friction modifier is friction modifier. Has anyone used this? Is this stuff good enough? Or should I find something else? Thanks.

- JyRO

 

I bought some Trans-X Posi-trac from Autozone and used it in my Dana 80 LSD with good results. I found that using a little less than 1 tube works well with my Mag Hitec diff cover and 5 qts of Mobile 1.

 

Just my opinion, the Ford limited slip additive is the best friction modifier out there.Be really careful the sfuff really smells bad,dont get it on you.You'll need 2 bottles for your truck.

 

Right now you can pick up Royal purple gear oil for $10.11/quart shipped to your door. No tax. www.karlracing.com. No friction modifier required with that stuff. Might be worth it for you. I just got mine.

 

Ive used many of the different synthetic gear oils out there and have always had to add a friction modifier to keep the cluthes from chattering.When they chatter you can do some damadge.

 

Oh yea? It says you don't have to use any on the RP bottle. We'll see...

 

I don't believe in taking chances........I get my from my local Dodge dealer. Why gamble on something that costs less than $10?

 

I'm going to wind up running Mobil 1 synthetic 75W - 90. And I WILL be running friction modifier regardless. I'm just trying to find out if there is a specific friction modifier that is recommended, or the stuff I mentioned if fine.

- JyRO

 

If you tow with your truck, you should use 75w140 synthetic - so says the manual for my truck - a 2002.

 

So should I run a friction modifier with my Royal Purple or not? Could that make it too slippery?

 

Let's see, I've got 118k+ on the truck now ... and it has the original diff fluid. I would say my truck has towed (rather heavy) for 2/3rds of those miles. Don't take this the wrong way, but why *should* is use 75W-140?

Personally, I think that I'm fine with conventional 75W-90. But I've decided to run Mobil 1 synthetic 75W-90. That should be more than adequate for my application as far as I understand.

- JyRO