So this is the information I got from RAVE,
Transfer box
Use Texaco Multi-Gear 75W/90R or oil meeting
specification API GL5

I assume this is the same oil used for the differential. But is there an easy way to replace the oil? Seems like I cant fit any tool behind or underneath to reach and remove the plugs. The filler plug is blocked by a cable or hose and its above the plug. Can that be removed? The drain plug, can that be removed without removing the cross bar right beneath it? Any suggestions to remove those or tools?
Thanks again

 

It is the same oil.

No, you don't have to pull the cross member to get to the drain.

The cable blocking the fill is the parking brake. Chock the wheels and release the brake. This should allow it to flex enough to get a ratchet behind it. 1/2 square drive (i think).

 

First try loosening fill plug, (the one behind hand brake cable), use 1/2" universal joint socket extension ,( to make sure you can refill after drain,) then loosen drain plug, don't need to remove cross bar,
Use your favorite 75w90 (GL5) gear oil, should need 2.2quart to refill,

 

The key for me was a wobble extension

 

I use 85/140w here in TX, but 80/90w also works. Yep a wobble extension helps a lot.

 

Bom2oo2 said it in passing but I want to emphasize it - ALWAYS remove or at least loosen the fill Plug before you remove the drain plug. On anything. It would be a drag to drain all the fluid and then not be able to refill.

 

X1 .............. a wobble or a short normal extension and a breaker bar.

 

Good tip min01. If original the plug is held in with some Loctite thread sealer. I use RTV when I put mine back but ONLY on the threads. The plug is a tapered thread so don't over tighten it.

 

X1 ......... agreed. Any quality oil be it synthetic, semi-synthetic or mineral will do and 80-140 keeps the box quieter also.

 

I actually went to a hardware store and bought a big diameter short bolt and ground down the threaded part until it was square and fit tight in the fill plug hole. After it was in the bolt head was flush with the back of the transfer case and I just used a 7/8 inch wrench to take the plug out, it eliminated the need for the wobble and the parking brake cable was not a factor then either