It's time to oversee the fluids in my '93 4x4 p/u.
The M/T and T/C should have API-GL4/GL5 SAE75W90.
Same in the front axle. For the rear diff it gets trickier...
I believe my truck came with an LSD factory rear end. Truck is actually europeean Volkswagen Taro (Toyota Hilux/Pickup assembled in Germany). I elevated the rear end and both wheels spin in the same direction when one is turned -> LSD?
The FSM specifies a special 75W90 LSD hypoid oil for that application. I can't seem to find exactly that anywhere. Castrol has a 75W140 as a recommendation. Do I dare to put that in there?

M/T will do better with GL-4 gear oil, t-case will work on pretty much anything:
- http://www.4crawler.com/4x4/4R_TechInfo.shtml#Fluids

GL-5 in the diffs, hypoid oil is basically GL-5 oil, hypoid refers to a helical cut gear like the ring and pinion. For clutch type limited slip, you can add a limited slip diff. friction additive if you get some chatter with regular GL-5 gear oil.

Did the exchange yesterday. Put Mobil fully synthetic GL-4 75W80 in the transmission, GL-5 75W90 in the transfer case and front axle. Quaker State fully synthetic 75W90 Limited Slip in the rear axle. Funny thing, when I was crawling under there I found a sticker under the dirt on the housing saying "Only LSD oil". I wasn't 100% sure the truck came with LSD from the factory but now I know. Gotta say the transmission feels smoother now <img src="/forums/images/graemlins/cheers.gif" alt="" /> There wasn't much metallic residue on the magnetic plugs. Hopefully the drivetrain will hold a few more years now! Too bad the rest of the truck has seen its best days <img src="/forums/images/graemlins/rolleyes.gif" alt="" />