pelexj90

noticed that my old zj had both fulltime 4wd and partime where as my 98 xj has only part time does do zjs technically have a better system?

Dan91

The full time 4x4 (NP 242) is just a system with a sort of differential in the T-case itself. It allows you to use 4WD on dry pavement without harm to the drivetrain. The NP231 (only has part time) should only be driven in 4WD on slick surfaces, wet roads allow for enough slip to prevent binding. The 231 is a stronger case however. I'd say for the average driver the 242 might be better, as you can put it in 4 full time and leave it. The 231 is probably better for offroaders being that it's stronger. There are XJs that came with the 242 but it seems to me that the newer models had mostly the 231.

XJ Knight

To add to this. Alot of ZJ's got the weakest of the Jeep transfer cases at that time in the NP249 case (Full Time 4H - N - 4L). The XJ never did get that transfercase. Most who offroad there ZJ's and have that case will wait for it to break and then swap in a NP231 Comand Trac

VTJeep

242's are convenient cause of the full time option
231's are stronger cause of the lack of full time

242's are better for DD
231's are better for wheelin

2KXJJEEP

so r all the np231 comand trac and what is comand trac

XJ Knight

Yeah it's just a cool term Jeep made up to call the NP231 transfercase. The NP242 is also know as select trac. I think the NP249 is Quadra trac. Jeep didn't think to hard with the NP241OR t case that is in all 03- present Jeep Wrangler Rubicons. They went with Rock Trac for that one lol

Rock Toy

The statement that wet roads allow for enough slip to prevent the 231 from binding in part time is only true if you have really crappy tires or if you are talking about wet dirt roads. You shouldn't run in part time 4WD unless you're on a loose surface.

2KXJJEEP

y would anybody run 4x4 on a wet roads...only time i run 4x4 is on snow covered roads or offroad

XJ Knight

some people are not smert

Dan91

Well according to the owners manual it's fine. Definitely no point to use 4x4 on wet paved roads though lol.