"Selec-Trac Full time 4WD system" is what is on the build sheet but no model number

I have this system on a 1991 XJ Laredo and cannot locate a model number. It is a 2 speed, Hi and Low range, but can be sifted on the fly to 4WD hi range full time without stopping. To go to 4WD Low or Hi range part time, you have to stop. 4WD on the fly is annotated in Green whereas other ranges are Orange. Have not seen another with this option. How common is it?

Dan

 

That's the np242 transfer case and it is common. You can shift back and forth between 2 hi, 4hi part time and 4hi full time on the fly. For going in and out of 4low you have to be stopped and in neutral.

 

The model # for the Selec-Trac is NP242. You can find this on the ID tag screwed to the backside of the transfer case. It is red and silver, and round.

 

Shouldn't have to stop to go into 4Hi Part Time since it's between 2Hi and 4Hi Full Time on the selector, so long as you're going in a straight line and not doing it in a hard corner.

 

I guess I will have to check the manual and see what it says, thanks for the response

 

YES! What I was going to say. You can't get to Full Time without going through Part Time.

Not quite sure why the Full Time position isn't right behind 2hi ???? Or why it even needs 2hi in the first place ....

Sometimes I wish for a Full Time LOW capability.

 

Shifting the NP/NV242J Selec-Trac Transfer Case

2WD Position
This position is for driving on hard-surfaced roads under normal driving conditions when 4-wheel drive is not desired.

4x4 PART TIME Position
This position is designed for temporary use of 4-wheel drive when on-or off-road conditions such as deep snow or heavy ice require increased traction. When engaged, both the front and the rear axles are mechanically locked together and turn at the same speed. Do not use 4x4 PART TIME on dry, paved roads.

To engage, shift transfer case from 2WD to 4x4 PART TIME while the vehicle is moving at any legal speed.

An amber PART TIME lamp will illuminate on the instrument cluster when 4x4 PART TIME is selected.

4x4 FULL TIME Position
This is the primary 4-wheel drive position, which offers better traction when roads are wet, snow covered or icy. When engaged, the front and rear wheels axles are permitted to turn at different speeds to enhance maneuverability. Use 4x4 FULL TIME year-round on all road surfaces if you wish.

To engage, shift transfer case from 2WD to 4x4 FULL TIME while the vehicle is moving at any legal speed. When shifting, do it in a swift and firm movement.

When shifting from 2WD through 4x4 PART TIME to 4x4 FULL TIME, two momentary releases of the accelerator may be required after shifting.

A green FULL TIME lamp will illuminate on the instrument cluster when 4x4 FULL TIME is selected.

4 LO Position
This position is designed for temporary use of 4-wheel drive when off-road conditions require added low speed pulling power. Do not use 4 LO on dry, paved roads.

To engage, slow the vehicle to 2-3 mph (3-5 km/h), shift the transmission into Neutral (N), then shift the transfer case lever to Neutral, then to the right and pull firmly rearward to 4 LO.

Never attempt to engage Low Range when the vehicle is moving faster than 2-3 mph (3-5 km/h). Transfer case damage may result.

An amber PART TIME lamp will illuminate on the instrument cluster when 4 LO is selected.

 

Thanks Appreciate the lengthy explanation that should help all owners.

 

My uneducated guess is that it's easier in terms of mechanical progression since it's almost identical to the 231, and trying to put FT before PT would have required extensive redesign.

 

Yeah, I suppose. But either position is essentially "4 high" with the exception that PT is locked and FT allows the center differential to operate. Not really knowing exactly how it works, it does seem that the center differential lock could have been associated with either position.

OTOH, I've pretty well come to the practice of either using FT (99%) or 4LO so it works out pretty good. I see no point at all to 2wd with this FT system because the front axle and shaft are always turning anyway. I can't see how it could take more gas to drive the front end with the engine than to drive the rear end only and then "ground drive" the front end. As far as wear, it might even be worse to have the front gears and TC chain floating than a steady drive from the engine?

 

I personally wouldn't have a 4x4 that didn't have a 2wd option. I don't want all the wear and tear on the front axle, you get better fuel mileage in 2wd, and you can't have as much fun doing burnouts and donuts in 4x4.

 

Well unless you have lock out hubs then the wear and tear doesn't go away.

But I'll leave the burnouts to you whippersnappers

 

There is a difference between the axle spinning freely, and actually being driven.

 

I wonder which one causes the most wear ???