How do you know what t-case you have?

 

easiest way to tell is to simply look at the selections you have next the t-case handle inside your XJ.
NP231's will have the following: 2wd, 4HI, Neutral, 4LO. When engaging either 4HI or 4LO, an amber "Part Time" light should come on in your gauge cluster.
NP242's will have the following: 2wd, Part time 4HI, Full time 4HI, Neutral, and 4LO. When in Full time 4HI, an amber "Full Time" light will come on in your gauge cluster. When in either Part time 4HI or 4LO, an amber "Part Time" light should come on in your gauge cluster.

The other way to find out is to get under your XJ and look at the rear of the t-case. There should be a metal badge with red lettering that will identify which one you have.

 

4full time= Drive on pavement (center differential in tcase allows different speeds between tires such as when turning.)
4part time= off road only (locks axles together so when turning the tires needs to slip on the ground.. ie dirt, rocks, snow, grass, etc)


NP231 has the following settings: 2HI, 4HI, N, 4LO
NP242 has the following settings: 2HI, 4 full time, 4 part time, N, 4LO.
84-87 XJs could also have come with an NP207 which it a part time case and would have the same shift options as the NP231.

 

Oh ok thanks, I don't have full time =(
So when should I use HI and when should I use LO?

 

Either can only be used off road. 4hi for regular speed requirements, 4lo when you need more torque to the ground.. such as crawling up a steep hill.

 

My handbook says I can shift into 4H PT or 4H FT at any speed but 4H PT is for Mud, gravel,ice etc (slippery) only.
4 LO can onmy be shifted into at 2-3 mph and used for towing or extra torque up a hill etc.

Stuart

 

Part time = non pavement only (mud, dirt, gravel, snow, ice), whether it be 4HI or 4LO. 4HI, whether full or part time, can be shifted into at any speed up to 45mph. With 4LO (always part time), come to a complete stop, put the transmission in neutral, and then shift the t-case into 4LO. Yes, the manual says you can do it at 2-3 mph, but it's better to come to complete stop.

 

Does anyone ever have issues selecting 4wd FT while on the move?

You have to go through PT to go to FT on the selector lever and 9/10 times mine will stick in PT even though I have selected FT

Nearly always have to stop and flick the gear lever between R/N/D before the centre diff opens...

 

X2.
Part-time is for part-time use...
Full-time is for full-time use...

 

thanks for help. iv been using my full time 4x4 in the 10" of snow we got on monday and i couldn't be happier

 

I hate to re-hash an old thread but Im going to blast the engineers on this one. To me, "full time" 4wd tells me that all 4 wheels would be locked and pulling, whereas "part time" would be what you would use on pavement or "normal" circumstances,One would even assume that by the position of the tcase lever and its labeling,but this is NOT the case with these 242s. Ive seen this topic on here quite a bit and I totally understand the confusion by noobies,including me, who have owned other 4x4s(I currently own a 93 nissan) I havent seen the mechanics of one to understand how it works so im speaking out of line, but what gets me is how you have to shift PAST the PT mode(full lock) to get to FT mode(normal 4wd). To me, these tcases are labeled for "conditions" rather than "mechanics"

 

You can drive on all surfaces in Full Time however Part Time is a direct connected 4WD and should not be used on dry pavement as it will damage the transfer case.

 

I agree with you trakr.

As for when to shift, the owners manual says that any legal speed is acceptable for shifting into 4WD.

What I find is that if you shift out of 4WD you will have to blip the throttle to loosen the axles so they can disengage. Just because you shift the lever doesn't mean you are in 4WD right away or OUT of 4WD right away. I'm guessing the coupler needs to slide off the splines and can't do that when under load. Same for uncoupling I would figure, but someone more knowledgeable could chime in.

 

I would also add using 4lo for descending a steep hill, as in compression braking, when you don't want to over use your brakes and slide off the trail.

 

Full time 4WD doesn't affect your gas mileage. All those components are rotating anyway, unless you put in manual hubs. The only difference is that in 2WD, the vehicle is dragging the front tires and the road is turning the wheels.