75w140 Differential

[GumbyJarvis]

I settled on the Valvoline. I also ordered the Mopar Limited Slip Additive.

Since the valvoline already has a limited slip additive, how much would yall add of the mopar additive? I'm guessing around 2oz, but what say yall?

 

[BrianF]

When I did the 9.25 in my now sold 2011 1500, I used a group 4 based 80w140 that already had the LS additive in there. As test, I added a few oz bottle of GM LS additive. What I found was poorer lockup under load. Unloaded, you could not tell when it engaged but under load with a trailer, the LSD could not lock up.

My second fill with the same fluid, I skipped the extra additive. Unloaded was no discernable difference but it would not engage under heavy load.

So my opinion is don't add any additive. Just add the fluid, put on some miles and see how the engagement is.

 

[DGXR]

By everything I have seen, the fluids with the LS additive work just fine on most vehicles that call for LS. If you use it and feel/hear chattering or stuttering, then add 4oz of the LS fluid. Personally I use Amsoil severe gear 75w90 in my Corvette and Tacoma differentials, it is great stuff. I do see 100F regularly in summer but I'm not towing or hammering the gas all the time. Valvoline is good, as is Mobil, as is virtually any other name brand synthetic gear oil. I am also curious why 75w140 is spec'd and not 75w90.