Differential Oil

[user 71196]

Much confusion I have over this. I am getting my rear diff (4.10 LS) oil replaced this coming week when my truck goes in for its other scheduled repairs. I will be replacing the oil with Valvoline 75w-140 Synthetic. It claims it already has the additive for the LS. Some people say its fine, others insist you still have to add the friction modifier. I searched here, and there is still quite a debate from the older threads. Just wondering what y'all think bout that now.



Also, for the front, the fluid is also claims its for LS diffs, as I'm getting a 75w-90 synthetic as well. Will that matter as the front does not seem to need any friction modifier at all? Or should i just stick with 80w-90 conventional oil?



Once again, my thanks to y'all in advance. :haveabeer:

 

[Vic Sorlie]

The LS additive is not normally needed with AMSOIL gear lubes. You can add it if desired (we have the product, see web site). Severe Gear is also available in 75W-90 and 75W-110. Wholesale pricing available by using Pref Customer program. PM me for details or see my website.

 

[Jeffksf B]

I've used Valvoline synthetic as well and have always added the Motorcraft LS additive. The one time I used an additive from Autozone it made noise. Added the Motorcraft stuff and noise went away. The front diff doesn't have a limited slip Diff so no additive needed up front.

The motorcraft stuff is only $6 or $7 bucks at a dealership.

 

[EddieS'04]

I would still use the motorcraft additive. My 'stang had a motorcraft LS. I changed the lube to mobil 1. It also said, additive was in it. The LS unit kept chattering, until I put in a bottle of motorcraft additive. Then did some slow figure 8's in a local parking lot.

 

[Todd Z]

ALWAYS ALWAYS ALWAYS ALWAYS ALWAYS ALWAYS ALWAYS ALWAYS ALWAYS ALWAYS ALWAYS ALWAYS ALWAYS ALWAYS ALWAYS ALWAYS ALWAYS ALWAYS ALWAYS ALWAYS ALWAYS ALWAYS ALWAYS ALWAYS ALWAYS ALWAYS ALWAYS ALWAYS Put in the extra bottle....



Just saying.



Todd Z