Can anyone tell me what kind of gear oil and transfer case oil i need for a 1998 Dodge Ram 1500 4x4. Is it the same or two different kinds.

 

Front differential - 75W140
Rear Differential - 75W90
Transfer case - ATF (Automatic Transmission Fluid) - I use Royal Purple ATF

 

Don't use anything but ATF+4. If you use regular ATF, which is not designed for Chrysler transmissions, you are asking for problems later down the road.

My manual says to use 80w90 in the rear differential, not 75w90. However, that would be close enough that I don't believe it would matter any.

 

Royal Purple is synthetic and it comes in a single rating - universal.
Plus his question was regarding X-fer case not transmission.
It is OK to use ATF+3 in a X-fer case.

 

True, the transfer case isn't as picky (supposedly).

But a lot of those ATF brands come in one "universal" ATF. Universal, or whatever, ATF is not the same as ATF+4. You are still asking for problems later down the road if you use "universal" ATF in the transmission. And I'm not saying Royal Purple is bad, BTW, just that regular ATF is not what our trannies need. The same tranny fluid that works in a Ford or GMC transmission will not work as well in our picky stock Chrysler trannies.

But, again, I don't think it'd hurt the transfer case.