Transfer Case Question NP242 vs NP231

[cruiser54]

Are you shifting it properly?

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.

[Lost_Wrench]

Yes, I am shifting properly. This is the 5th Cherokee I've owned in my lifetime and I'm very familiar with the 4wd system of the NP231, but this 1998 XJ is the first I've had with the NP242 w/ Full Time option so I wanted to make sure I wasn't doing something wrong. Turns out I'm not, so it's time to take a closer under the vehicle look to figure out what's wrong. Thanks for the help everyone.

[cruiser54]

The 242 is finicky compared to the 231. All 4 tires the same size and pressure?

[1990JEEPXJ]

Sounds like it’s not quite getting out of full time. Which would be only marginally better than 2wd in very low traction situations. Part time should be no different in 231 vs 242

[Lost_Wrench]

It's very clearly going between 2wd and Full Time with no issues which is good because I can at least still drive it in winter conditions just fine, and I agree, full time is not great otherwise as my deep snow test revealed. It's good enough to *maybe* get you unstuck in situations where the tires are just spinning while in 2wd.

[maxbraketorque]

Seems a bit puzzling to me that its not going into 4PT. Its necessary to pass through 4PT to get to 4FT. Would seem strange for the TC to be in 4FT when its set to 4PT. Would be nice if there was a clear diagram of the NP242 to show the torque transfer path in each of the different modes, but I haven't been able to find one. Have you tried disconnecting the linkage from the TC shifter arm to see if the TC can be shifted into 4PT using you hand from underneath?

[1990JEEPXJ]

Originally Posted by maxbraketorque

Seems a bit puzzling to me that its not going into 4PT. Its necessary to pass through 4PT to get to 4FT. Would seem strange for the TC to be in 4FT when its set to 4PT. Would be nice if there was a clear diagram of the NP242 to show the torque transfer path in each of the different modes, but I haven't been able to find one. Have you tried disconnecting the linkage from the TC shifter arm to see if the TC can be shifted into 4PT using you hand from underneath?

The full time mode just makes the transfer case an open differential like an axle so there is no real regulation of torque as it will only be traction dependent and send power to the axle with least resistance. In theory, you could still spin only one tire while in full time. There are no clutches to assist with splitting the torque front and rear.

[maxbraketorque]

Yep, I understand that aspect. I was trying to find info on the physical design of the NP242 diff to show how it switches from differential mode to locked mode.

[Rob Mayercik]

Can you download a service manual from NewProcess/NewVentureGear?

If memory serves, the XJ FSM has some degree of rebuilding information, anything useful in there on this?

[75SV1]

Originally Posted by Rob Mayercik

Can you download a service manual from NewProcess/NewVentureGear?

If memory serves, the XJ FSM has some degree of rebuilding information, anything useful in there on this?

I am attempting to rebuild a NP242. I have an '00 FSM. It seems complete on the rebuild procedure.

[maxbraketorque]

If you've got an NP242 on the bench, I would love to see some photos of the component layout that produces 4FT and 4PT.

[Lost_Wrench]

I would also love to see that.

[Jason77]

Same here, I’ve rebuilt a 231 but never seen a 242 apart. I’d like to see how it’s different.


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[Lost_Wrench]

Update:

So my NP242 T-Case in the '98 XJ was only operating in 2WD or Full Time. Part Time High and Low were not engaging, despite the dash lights showing the correct position for all. I finally got around to diagnosing yesterday and I feel like a dummy, but the simplest solutions are often the likeliest culprits. I drained the T-Case and there was less than a quart (20oz) of nasty dark fluid. Filled up with ATF and now all 4x4 ranges work and shift fine. Thanks everyone, Tim_MN and whoever else recommended a fluid change were correct.

I purchased this Jeep last September and all 4x4 ranges were working until December-ish. Makes me wonder if the fluid had ever been changed. It was so dark and disgusting I wouldn't be surprised if it was old gear or motor oil from someone topping it off with whatever they had in the garage. T-Case doesn't appear to have been leaking at all so who knows why it was so low? Why Full Time still worked with such low fluid is a mystery that only those with intimate knowledge of the NP242 would probably know. If that's you please share. Thanks all!

[cruiser54]

Please don't take offense, but I'm gonna use your post as an example.

ALWAYS check fluid level and condition on any "new to you" vehicle.

do a used car inspection like the dealers do on trade-ins.