I decided to run the traps on some info I came across in a post recently re: the proper weight rear gear lube for the AAM axle. I called American's 800 number and spoke to Bob Dunn. He verified that we should be using 75/90 weight and it should be full synthetic with NO additive. DCX puts 75/140, I understand, in these rear ends. He said they've been trying to get that corrected for 2 years,....go figure. I for one was interested since I put a Mag Hytec cover on and filled it with the wrong stuff and also put in the additive. Thought someone else could benefit from this info. The proper DCX part number for the right fluid is 5102232AA.

 

Did he say additive was not nessecary or did he say they should not be in there? Some gear lubes such as Amsoil come with friction modifiers already in them. Is he saying they should not be used or that they are not necessary for the AA axle?

Sorry I should have read my post before sending it. I asked the same question twice.

 

I read another thread that said this is NOT a clutch type limited slip, it's a Torsen design I guess. That means no additives just good lubrication. But, what I wonder is will the additive hurt if it's already in there?

 

He said,.."Synthetic only,..no additive". Will it hurt if it's in there? Hope not,..I've had mine in there for 3 months.

 

The modified friction additive for clutch type differetials will NOT hurt.

 

I talked to the same Bob Dunn at AAM today and he said that the only concern about the additives was one of possible long term effect of possible seal degradation. He said there are no clutches in their axle. I then called Amsoil tech section as that is what I was intending of using and they say they have done research on the American Axle and that the additives in their gear lube will not harm the seals. I am sure they have not done very long term testing but I believe I will go with the Amsoil when I change.

 

i could swear my owners book says the gear oil is 75w90...? that's what i topped up my front and rear diff's with [they were both low from the factory ]

 

Has anyone at Amsoil ever said that their products are not OK for just about any application?

 

smiller

No I do not think that they have or will for that matter. That is kind of what I was hinting at when I said that I was sure that they had not done very long term testing. Just did not feel like comming right our and saying it. But like I said I think I will go ahead and use the Amsoil gear lube.

 

75W/90W full synthetic is the specified lube for the Gen IIIs. The 75W/140W was the specified lube for the Gen IIs. I used the Mobil 1 when I changed both of my diffs. You can get it at Advance Auto Parts.