OOps my friend got a 1991 xj and changed all the fluids but he put in 90w gear oil in his NP231, he hasn't put it in 4 wheel yet so can he just drain it and put in Dextron 3 and be OK? ...Tj

 

The NP231 is a pretty dumb piece of equipment. He can simply drain it and refill and be just fine. He might want to consider doing a drain/refill.. run it a few miles to get it warm and do the drain refill thing again.

 

Ya drain and fill would be fine. I've talked to guys in Desert area's that run a think gear lube in them to keep them from over heating. So a drain and refill should be just fine..

 

Thank you very much, he was used to his NP 205 and just thought it took the same I think...Tj

 

Hate to disagree with my colleagues above but the transfercase has an oil pump built in and as heavy as the gear oil is I would disassemble it and clean everything and replace the pump. Just my

 

It does have a oil pump, but don't see that needing to be replaced.. I guess it would be a personal preference on that one..

Now I just did a search and some reading on this topic and it seems that both are used, pending on who puts it in. Yes ATF is what the OEM calls for, but there seems to be many people using gear lube because it is thicker. And I could not find any one ever having to replace the oil pump in the T-case.. So if your going back to ATF you should be fine to just drain and refill.

 

Nick is right you will probably be just fine but I am a little scared when the wrong fluid is used and that is just me.

 

I have heard of people going as thick as 10w-30 motor oil and not having problems, but that is in seriously warm climates.