Gear oil in the transfer case?

[jvrotter]

Back somewhere around the early 90's my M1008's transfer case went belly up and I had to change it out with a surplus unit. My Dad who was an old farm boy suggested that I put 90wt gear oil in place of the tranny fluid. I been running that ever since. Any concerns on doing this?

 

[Cucvnut]

dextron 3 works.

 

[overkill375]

ATF is what you are supposed to use in all the GM Alumnium cases I know they used gear oil in the older 205 and 203 cases.

 

[jj]

Seems if you've been "running 90wt since the 90's" and the transfer case is still working, you've already proven the concept. Now i know what to do with the balance of the five gallon pail of gear oil on my shelf!

 

[taquito971]

Based on my limited experience with these old trucks, I have found that the manual usually calls for whatever is in the transmission to go in the transfer case. My truck (not a military unit) called for 90wt in the transmission (SM465) and 90wt in the 205 t-case. My Suburban called for Dex-3 in the T-400 and 208.

Brian
(Not an expert)

 

[Terracoma]

I've noticed the same thing as Brian, same fluid throughout the driveline.

Makes sense, as it eliminates any possibility of two different viscosities mixing and also simplifies materials requirements for servicing.

 

[Cucvnut]

the only tcase that can have issues like that is a 242 from a Humvee that has transmission to tcase drain back issues,.

 

[jaxsof]

my 01 Dodge calls for ATF in the T-Case, nd synth gear oil in the trans. They went to the atf in the t-cases because 90wt doesnt flow very well in sub 30 temps. it really doesnt help anything if it cant get to where its needed. On a side note, they went to atf in standard transmixers in the 80s because machining had gotten so good, the thick oil wsnt allowing shifting at low temps.