np231 diagnose

hey all
trying to figure out what is wrong with the 4x4 on a 91 XJ.

4.0/ax-15/np231
when shifting into/out of 4x4 it shifts smooth and nicely, but in 4x4 it jerks and jumps sometimes. this granny owns it and never used 4x4. im guessing the oil pump in the t-case died? any guesses? its not mine or i would tear it down and rebuild it.

-tim

edit: i think the chain is slightly stretched due to the oil pump wearing out possibly

, but in 4x4 it jerks and jumps sometimes. this granny owns it and never used 4x4

Click to expand...

I would start with the front axle, u-joints or Vacuum disconnect,

langer1 said:

I would start with the front axle, u-joints or Vacuum disconnect,

Click to expand...

ok, my trail xj does not have vac disco, so i am not familiar with it.

also, i did not think it was the u-joints because i was going straight in wet grass when testing it. could they still do that in a straight line?

thanks
-tim

might want to check the linkage and see if its popping in and out of 4WD.
Have you checked for slack in the chain by turning the front driveshaft with the front wheels off the ground? Mine moves about 1/4" inch, anything more and I'd suspect chain.
Hae you checked the fluid level in the t-case?

The chain runs in oil so the oil pump would have no effect on it.
I think most t-cases fail because they're empty and theres to oil to pump to the top where it's needed.