Diff and Trans fluids the same?

Doing some reading around the internet, it seems that the T-90 transmission and the T-18 transfer case both use the same 80w-90 gear that I was told to put in the front diff. When I refilled the diff, I noticed that the oil was black, not golden like you'd see with std motor oil. This is new to me so I found it interesting that the gear oil was black. Well, the other leak I have been needing to address is coming from somewhere above the skid plate beneath the tranny. The fluid on the garage floor from this is more like regular transmission fluid. Kinda clear/golden color. Think I got the wrong fluid in there?

 

Most likely it's contaminated oil (black).. Change all of them with good quality 80W-90 and you will be fine.. the only caveat to this is to make sure you do not have a limited slip diff. This wil require either friction modifier or just using oil for LSD..

Bubba

 

Yes, it's in the archives and the correct fluid is available from NAPA but I think you have to order it. The old thread gives the NAPA part number.

 

your leak in your d18 is most likely coming from either the rear output shaft or the speedometer cable box...thing....i cant think of the name of it right now

 

after a bit of searching i think you are talking about this right hurr
http://www.napaonline.com/Catalog/CatalogItemDetail.aspx?R=SLCSL24239_0006410049

part number: SL SL24239

 

I don't recall the thread title, and it may have been on a competing forum, but a member posted up a comparative chart of different gear lubes corrosiveness, using a pure copper plate and checking the color change on the copper after exposure to the test sample of gear lube as a gauge of its relative corrosiveness.
The best one of the bunch was Redline MT 90, a GL4 class of gear lube.
Napa can order this for you.

Don

 

I thought a T-18 was a transmission???

 

Thanks for the wealth of information. I'll have to order me some from NAPA, although I am not sure we have one here locally.