RockinJohnny

I am trying to change fluids on the differentials and I am having trouble locating replacement gaskets for the differential covers. The reason I am removing the covers is that I swamped the axels and the fluid is now tan in color.

My rear axel is a 11.5 inch and I don't know how to tell what the front axel is.

DBLR

Factory gaskets are reusable if you don't tear or cut it when taking the cover off. IIRC the front is a 9.5 inch.

93-331-29psi

permatex black. I don't think I've ever put a differential gasket in anything I've ever owned.

Dr.Dizzle

Like DBLR mentioned,You can reuse the gaskets. Make sure to wipe off the gaskets and the mating surfaces prior to installation.

RockinJohnny

How many ounces of posi additive do you add to the 11.5 inch differential?

ripping r

you dont need it.

RockinJohnny

May I ask why you wouldn't use posi additive in a limited slip rear end?

ripping r

i have the limited slip rear. they use gears not clutches. so no additive is needed.

Dr.Dizzle

Exactly. The service manual does not recommend the use of friction modifiers with the AAM units.

p035970

Some axles chatter though. If your axle is one of these, the additive will stop the grinding sound.

Strea

Okay, I bought Mobile 1 75w90 LS synthetic gear oil. Will this hurt my truck. Not sure I understood what the LS was for?

Thanks,

Strea

Oliverpuller

Strea, that is exactly what I changed my axles out with just this past weekend. Mobil 1 75w-90 LS. 16,500 miles on truck factory fill in front and back looked the same, slightly dark gray in color.

singleturnout

Bought some Mobil 1 75-90LS is it ok to run this in the diffs or should i go back and get the regular 75-90,wasnt paying attention when i bought the gear oil

TexasCTD

Mobil 1 75w90 LS is fine. As long as it is GL-5 rated, any synthetic 75w90 brand gear oil is fine.

I have been running that fluid for 121,000 miles no problem since I first changed out my factory fill at 15K. 136K now on the truck. I change it every 20K miles or so now and it looks like new.

..

bradler

re-use gaskets. make sure to clean around gasket/mating surface real good before pulling the cover unless you want to clean sand out of the gears. don't ask how i know this. and look for a fill line on the cover some people fill em to the bottom of fill hole but there is a fill line on some covers...