Hi, decided to save my friends 89 3.0L 5speed Dodge Raider from the junkyard...has over 388K kms on it and a few rust issues around the wheel arches. I will be doing the basics first...full tune-up, fluids, brakes, suspension, and some minor body work and fender flares.

The factory service manual recommends GL4 or higher for transfer case and manual trans, and GL5 or higher for the front and rear diffs (LSD additive for rear diff required). The temp index in the manual recommends 80W90 down to -23C, but i want an all season oil that goes down to -35C or so. My question is, i was going to go with 75W140 synthetic GL5 in both diffs, transfer case, and transmission. Then i saw a post here yesterday that someone said to only use GL4 in the 1st gen transfer cases or transmissions? Isn't GL5 better?

GL4 works fine. The most important trick is to use lsd additive (friction modifier) in the rear diff IF you have lsd for sure. There should be an orange sticker on the drivers door jamb that tells you, maybe on the diff, too. It keeps the lsd from giving you a shudder when turning a sharp corner as the lsd gets too aggresive.

ya any of the oils ive looked at have the LSD friction modifier in them so i'll make sure it is for the rear diff.

most oils are GL5, will GL5 wreck the TC and trans? manual says at least GL4

75W140 good for all?

I would NOT put GL5 in a Mitsu transmission. Only GL4. Plenty of research here to support this.

Regarding transfer case? Gl5 is fine. There are no synchros in there.

Gl5 in tranny... loss in shift quality. Best get a strict gl4. But based on the mileage it might not matter?

Oh, and dffs? I wouldnt put gl4 in there. It lacks the sulfur and shock additives to lube the gears properly.

ok, thanks guys

- GL4 for trans
- GL4 or GL5 for transfer case
- GL5 for diffs and make sure LSD additive for rear

Any recommendations for oil weights for a cold Canadian climate (cold winters, hot summers)...im still thinking 75W140 or might just go with conventional 80W90.

GL4 was a pain to find. Finally asked at NAPA counter and they ordered it in.

what about the oils that meet requirements of GL4 and GL5?

I think of it this way.... gl4 is an oil. Gl5 is an oil with a ton of sulphur. In the 70s??? diffs were running gl4 (and didnt last too long either I hear) so in that case they mean I will meet gl4 specs for a diff.

But for a tranny of this design the sulphur makes things too slippery and synchros wont engage well. (A rebuilder even told me strait 30w oil will do well as no sulphur and same viscosity as a 80w90 gear oil) You wont damage anything, but if your going through the effort might as well opimize quality.

Regarding options. As above, Napa stalube.... or order online. Something like redline mtl. I also found a Dodge dealer on ebay liquidating synthetic gl4 for NV4500 transmissions at like $4 a quart. Or if you dont plan to keep the truck for long, just pour 30w oil and be done.