Yep, I have done it. Heres how.........
This is how we upgraded my “command Trac” part time 4WD to “Selec Trac” full time 4WD in my Series 1 Jeep XJ. The donor vehicle was a 1994 4.0 Limited, and mine is a 1996 2.5 TD Limited.
I believe that its possible to do this upgrade in both Series 2 XJ’s and Grand Cherokees as well, but the process may differ slightly.
Background.
The Diesel Jeep Cherokee for the UK market, is usualy fitted with the NP231 Transfer Case, which only has "Part Time" 4x4 modes. The reasoning behind this is that it is a stronger Transfer Case, and more able to handle the higher low end torque of the TD engine.
The drawback is that the truck can sometimes fell a little "ungainly" on the road, especialy in the wet, given the high centre of gravity and the fact that you only have rear wheel drive.
My reason for wanting the upgrade was purely for improving the trucks "on road" manners. I feel that the benefits of this far outweigh the slightly weaker strength of the 242 compared to the 231 in off road sittuations.
It's worth noting that in the USA, it is common for XJ owners to replace the 242 T/C with the stronger 231 or simmilar to improve the rock crawling abbility of their trucks.
Parts List
1 x NP242 Transfer case.
The slip yoke from the donor vehicles rear prop.
1.4 litres Dextron II ATF Fluid
3.3 litres 75w90 GL5 Gear oil
The surround and “Position indicator plate” from around the Transfer case selector lever from the donor vehicle.
A new rear output seal for the new transfer case
The “part time” lamp connector, and as much of the cable as you can get from the loom of the donor vehicle.
1. First, drain the fluid from both the gearbox and transfer case.
2. Disconnect the front prop shaft. We did this at the front diff, as the case we were using already had the prop fitted.
3. Disconnect the rear prop from the rear diff, and pull the slip yoke out of the rear of the transfer case. Have a rag ready to catch any ATF fluid that may leak from the rear of the T/C.
4. Disconnect the two plug connectors (one for the spedo and one for the “Part time” light). Also disconnect the T/C breather from the top of the T/C.
5. Support the gearbox on a trolley jack, and raise it just enough to take the weight off the gearbox mounting.
6. Remove the four bolts attaching the bottom of the gearbox to the gearbox mount.
7. Remove the four bolts holding the gearbox cross member from the chassis frame rails, and remove the cross member from the vehicle. NOTE, of you have a T/C skid, you will need to remove this before removing the cross member.
8. Lower the gearbox gently on the jack, allowing you to access the bolts on the top of the T/C. Be careful not to lower too far, for fear of damaging engine mounts or linkages under the hood.
9. Disconnect the linkage to the control lever. This just pops out of the plastic bush with the help of a small crow bar.
10. Remove the 6 bolts holding the T/C to the gearbox.
11. gently pull the T/C backwards off the output shaft of the gearbox, and remove from the vehicle (It’s a good idea to have someone help you with this bit)
12. Fit the new output seal to the new T/C
13. Remove the slip yoke from the rear prop, and replace it with the slip yoke from the donor vehicle. We used a vice to push the joints open on the original prop, but had to remove the S/Y from the donor prop with a little help from an angle grinder.
14. Cut the plug off the “Part Time” lamp connector (it’s the one with only 2 wires) and use the one that you removed from the donor to extend the cable by about 5 inches. If you stagger the joints in the wires, and use a small crimp connector, it is possible to cover the joint with a length of corrugated sheathing (heliflex) that you saved from the donor car.
15. With the help of a friend, lift the new T/C into place, making sure it slides smoothly onto the gearbox output shaft, and make sure that the bolt holes line up.
16. Now, the rest of the installation is pretty much the reverse of the removal procedure.
17. Fill the T/C with new ATF. When mine had exactly the right amount in, it just started to dribble from the filler hole.
18. Fill the gearbox with fresh gear oil. You may find that a 5 foot length of clean hosepipe with a funnel attached is useful here.
19. Inside the car, remove the trim from around the 4x4 selection lever.
20. Using a Dremmel with a cut off wheel, or a sharp hack saw blade, remove the little lug on the metal gate that the lever comes through (if you don’t do this, full time 4x4 is right on top of the lug) and file smooth.
Before
After
21. Replace the trim with the one from the donor.
22. Make sure that you can get all the positions on the new T/C, and that the “Part Time” light on the dash functions correctly.
23. Road test, then check for leaks, loose bolts etc.
24. Smile the next time you power round an island in full time 4x4 in the rain
If it helps, I have a spare 242 transfer case, rear prop and an ally wheel for sale for a lot less than you have been quoted
