How can I tell which transfer case I have?
I have a '91 XJ 4.0 auto w/ D35 rear end.

 

if you have full time 4 wheel drive you have the 242 if you dont you have the 231 if you dont understand that go under the jeep there is a red circular tag on the driverside of the tcase towards the back of the vehicle it will say either 231 or 242

 

get underneath your Jeep and take a look. there should be a little metal tag on it that will tell you which one it is.

 

If your transfer case gear shifter thing (to the left of your P,N,R,4,3,L shifter) has the Full time 4lo option, then you have the NP232. If it only has part time 4lo, then you have the NP231.

 

Hmmm! Well the transfer shifter shows
2WD
4part time
4full time
N
4Low
So this means I have a 242 or 232?? How good or bad is that??
I check for a tag and can't find one.

 

you have the 242

 

OK Next question What is the difference between full and part time?? I'm just use to 4Hi and 4Lo

 

The np242 tc has a central lockable differential. In 4x4 full time the diff is unlocked and you can drive the jeep on every surface including asphalt. In 4x4 part time the diff is locked and you can drive only on loose and slippery surfaces.

 

Bingo.