Alright, all the books seem to have a different opinion...

Truck is a 2001 Ram 1500 4x4 5.9 engine.

Haynes says Dex3 for transfer case, factory service manual says ATF+4. Which is it?

For differential lube, Haynes says 90W and factory service manual says 75W-90. Opinions?

Thanks.

 

t-case -> atf+4.
diff. -> doesn't matter. its all GL-5 rated. further complexity is the front diff specifies 75w-140 synthetic. i just use 80w90 or 85w90 in both.

 

Dex III or ATF+ either is fine. ATF+ is better.
Chrysler back spec'ed ATF+4 to replace all earlier ATF+ and many Dex III applications.
Use 75w90 in the diff or 74w140 synthetic if you tow.

 

When I had my '98 RCSB 1500 5.9 4x4, I'd use ATF+4 in the transfer case, Lucas 75W-140 conventional in the rear (towed a bass boat regularly), and 75w-140 Mobil 1 in the front.
Reason for the dino oil in the rear was, just like in my current 3rd Gen, I had an Auburn LSD, which specifically says NOT to use synthetic lubes with it.

I do almost the same now, except I've become a believer in Royal Purple, so I run that in the front diff and everywhere else except the rear pumpkin...

 

It probably doesn't matter now but, the factory holds your warranty, not Haynes. That Haynes manual is probably for a wide range of years and their recommendations may be from the earlier years in that range. Plus, the factory manual has probably been updated more recently.