jjax

2004 FX4 5.4 w/B6 axle 133k

Got the fluids changed at a shop that many locals claimed was the best around. Did my research on here before to see if it was something I wanted to do and decided that right now, it was best to take it in. When I dropped it off, I wanted to ask some questions but got the, "ya,ya we got this" attitude. Shoulda walked right there but I decided to trust the public.

They did the transfer case with Amsoil Syn ATF. No problem there.
But did the front and rear diff's with Amsoil Syn 80w-90 and no friction mod.
From what I've read, seems like people here suggest:
75w-90 syn in the front and 75w-140 syn & friction mod for the rear.
Some folks on here say the friction mod is a must in the B6.

Question is, Should I got back and complain or is it really not that big a deal?

Thanks

Mod (Ret.)

Some synthetic differential fluid manufacturers state that friction modifiers are not required, and some folks will still add it in for what they call "insurance".


Is the rear end making any noises, or are right and left turns making the rear operate strangely? If not, then let it be.