I just put in a brand new truetrac and gears after blowing the Posi in millions of pieces and I was wondering what oil is the best for it? They put 75/140(same as stock as I believe) in it and I'm going to do an oil change soon soo should I stick to that oil or not?
I was also told by a guy at the dealership that if I changed oil type the bearings would let go(all new ones though) but w/e...what do yall think about that?

 

they say to use conevtional oil not the synthetic for the truetrac i think its 90w er something if you go to thier website it tells you exactly what to use.

 

I have a Truetrac sitting in my garage waiting to be installed. Before I ordered it I called Eaton and spoke to a rep. He said to use the same weight oil specified by Ford, but make sure it is NOT synthetic. In the case of my truck it is 75w140.

 

I don't think you can get 75W140 that is NOT synthetic.

I just looked in the Valvoline catalog, and their standard gear oil is available in 75W90, 80W90, and 85W140. If you are in the cold North, I'd probably use the 75W90. If you are in the hot South, I'd probably use the 85W140. However, I seem to remember people here saying that Eaton has told them to use the 80W90.

 

[QUOTE=glc;3925520]I don't think you can get 75W140 that is NOT synthetic.

I guess I would have figured that one out when I went to do my install. I suppose I'll be going with 75w90. I remember the Eaton rep specifically saying I can use whatever Ford wants, just so long as it is not synthetic. Since there are only gears and no clutches in the rear end, I don't see any problem with changing the weight. This also means that 07F150OAKLEY is running synthetic fluid and should definitely change it.

 

I was told the same thing by the Eaton rep. He recommended 80w90 because I live in Canada and it gets colder here but for the US he said 70w90 or is it 75w90 would be fine, but NEVER put synth in with the trutrac. I ran 75w140 for 2 days after the install and the rear whined like crazy, changed to conventional..silence.

If anyone wants I can PM the #800 number at Eaton , this takes you to the right guys so you don't have to make 4 calls to find the right dept, like I did.

 

I thought the Ford recommended oil was synthetic.

 

Yes, the Ford recommended oil is synthetic, but Eaton says do NOT use synthetic with their products. If you want to play with aftermarket stuff, the aftermarket manufacturer's recommendation takes precedence.

 

Still I am confused....I called the dealership again and they confirmed that if I put 80w90 that the bearings would not hold on 4 long sooo now i'm all confused what oil to go with....does it really NEED 80w90 or will synthetic actually damage it?

 

personally i think i would go with what eaton says to use i find it hard to believe ur bearings will go bad. when i get my true trac im gonna use what eaton says to use. its all up to you though

 

OP --- When I get home I'll pm you the #800 at Eaton and you can ask them directly. All I can tell you is once they took out the synth and put in the 80w90 the loud whining noise went away.

 

Myself when I put in my first diff(eaton posi) I had 80w90 w/lsd additive and went clubin' in montreal and on the way back it started whinning bad and when brought it 2 the shop n' opened it up the pinion bearing were screwed! When I blew the posi up(litterally in pieces) Eaton sent me a trutrac on warranty(SWEET) n bought new gears n' all the bearings and the guy I always buy from told me that if I put non syn. oil that my bearing would go bad again! Anyhow I'll call customer support and see what they'll say about it!!!

 

Eaton, the company who makes the limited slip, says non-synthetic oil. The guy you always buy from, who had no hand in designing the True-Trac says the other. I think I would believe what Eaton says.

 

I also don't think you are supposed to use LSD additive in an Eaton.

 

THE EATON POSI requires lsd additive not the trutrac.......anyhow I'm gonna get this figured out on monday!!!!