Hey guys , need some advice on what to use in my rear diff.Iwas thinking of going with 85/140.My rig has 64,000 miles on it and we rv fulltime and drag around a 14,000 lb. 5th wheel rv.Don't remember what I used last time.From what I've read everyone likes redline,schaeffers,and royal purple.It's confusing.Also what to use in my 6 speed manual tranny?Last time I changed I used Pennsoil synchro mesh.Thanks in advance.

 

Welcome newbie. Oil questions are the "best".... Lots of passion involved. When you've got some free time, try a search - you'll be awarded with many hours of entertainment. Its all confusing, and all good - I prefer to use syn oil all around.

Anyways, in the diff's I'm running 75W-90 in the front and 80W-140 in the rear; and will change them out soon with the same stuff.

For the tranny I've used both Redline MTL (in it right now) and Amsoil MTL; the shifting qualitity improved with the new oil, but I thought the shifting was better with the Amsoil - I'll put the Amsoil stuff back in the next time.

Since I'm under the truck changing out the differential fluid, I go ahead and change out the transmission and transfer case as well. Its easy and not that expensive.

hth.

 

There's some other threads about lubes right now. I'd use 80 or 85w140 for what you're pulling. I've had great luck with the RP - theirs is 85w140. I've used Ams MTF in the 6sp and liked it. I think I got 5 qts of MTF delivered for about $47. Park on a sidehill and put in all 5 qts. Then I had warranty work on the 6sp and the dealer refilled with 4 1/2 qts of DC stuff and I added another qt. and it is much quieter and shifts like silk. No matter what DC says about running forever with the 6sp lube, I'm changing at least by 25k. Craig

 

Who is running RP 85W-140 in the AAM 11.5" rear axle? How is it performing?

 

I've read a few guys are doing it and they really like it. That will be my next change and I will check temp and also try higher levels and check temp. Craig

 

i used 85w-140 royal purple....its great