Hey i have a 1994 XJ with a manual and a np231 thats gotten jammed up and no longer shifts, and i have a parts jeep with a np242. I'm wondering besides being mechanically more advanded therefore prone to failure a bit more than the 231 is there any reason i should just stick with a 231 over the 242. I really like the idea of the awd function but i want to make sure the gearing ratio for the low gear in the 242 is the same as the 231

 

242 has a much higher crawl ratio, much higher torque in the low gears, 2.71:1, vs 2.56:1. 242 can also have slippage in the driveshafts because it uses pressure to lock them together. Both transfer cases have advantages over each other, just depends on what you plan I believe SYE kits for the 242 are way more expensive then for the 231, if you go that route,

 

I have read where people say the 231 is slightly beefier.
I want to swap to a 242 but my '00 is just a DD and think it would be a little better to get around in the snow so......

 

They both have the same 2.72 low range and when in part time 4x4 the NP242 locks the drive shafts together the same as an NP231, the main difference is the NP242 has a full time 4x4 mode that uses an open differential in the transfer case so you can drive it on pavement. The NP242 is also weaker than the NP231 even though the numbering would imply otherwise.

 

The advantage of the 231 transfer case, in my opinion, is a bit more simplicity, less weight, and a smaller size. The 242 is physically larger and taunts the big rocks poking up at it from below. The aftermarket skid plates usually do not accommodate the 242.

The full-time 4wd only has an advantage when driving on snowy/icy roads. It is better on the highway to not have the front and rear axles locked together. Or if your wife isn't sure on which to use, the full time is a fool-proof thing to use.

I have seen failed 242 cases, but not a 231 case. But that's not saying much because I usually find myself working on smaller passenger cars than 4x4's. I am sure they both fail from time to time. As far as crawl ratios go, I am unsure of the differences between models / years. I have a 242 in my '99 XJ. I have 33's and 4.56 gears. I have zero complaints about the crawl ratio. I think it is perfect all the way to 13,000 feet elevation. I can darn near idle up most anything, but I have not yet pushed it to those places where I have all four 33's chirping on the rocks.

 

Oh thank you. Not sure why I thought the 231 was a lower ratio. I probably got it mixed with something else.

 

Another disadvantage of the 242 is that it has the predilection to not get out of 4x4 mode. My dad bought a brand new 1993 Grand Cherokee in late 1992 with the 242 and that was always the issue with it. Fast forward 30 years and I still find myself needing to drive forward and backwards a few times every now and then to get a 242 case to finally get out of 4x4. It was never a problem, but more of an inconvenience. My 231 rarely has this problem. I could see John C Public driving for a long time in 4x4 on a dry road, not knowing it, and the shift forks are scratching away the entire time...

 

Thats not to big of a deal for me mines mostly a 4x4 but also a DD but having to shove it in R then D to get it out of 4x4 is something i can deal with, and thanks to everyone else for the input. I think im going to just go ahead and do the swap since there aren't any massive downsides of the 242 from my point of view (other than beign way more complicated internally.

 

I had the same issue with both NP242s that I had and it is one of the main reasons why I swapped out my NP242 for an NP231, never had that problem with a 231.

 

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.

 

Here's how the factory suggests you shift the transfer case and I've been doing this since these things were new and I worked at the dealership. Quoted from the owner's manual. The suggestions in CAPS are mine.

"To engage, shift the transfer case lever from 2H to 4H while the vehicle is moving at any legal speed". I LET OFF THE GAS, THROW THE LEVER, TAP THE GAS AND LET OFF.

4L position: " To engage, slow the vehicle to 2-3 MPH , shift the transmission to Neutral, then shift the transfer lever to the right and pull firmly rearward to 4L".

TO SHIFT OUT OF 4L, SHIFT THE TRANSMISSION INTO NEUTRAL WITH THE VEHICLE STOPPED, SHIFT THE TRANSFER CASE LEVER TO 2H, THEN THE TRANS TO D IF YOU HAVE AN AUTOMATIC, OR INTO FIRST GEAR WITH A MANUAL, AND CONTINUE ON.

 

I would hope everyone on this forum knows how to shift a transfer case

 

You'd be surprised.

 

There's no hope. Sometimes visors are missing that had the instructions. Never an owners manual with an old vehicle. People are scared to shift the transfer case except at a complete stop because Uncle Bubba said it would explode if it was shifted while moving. . It goes on and on.

That's why I posted what I did. The first one is right out of the owners manual and the second one is mostly from the owners manual with my added comments.

 

I never had any problems with my 242; they are just as strong as the 231 in 4H part time and 4L, and have the same gearing. Maybe slightly weaker when in 4H full time, but no one should be driving too aggressively in that mode anyway. The only reasons you might not want one are (1) if you have a lunchbox in the front, full time becomes kind of useless, and (2) there's isn't nearly as much aftermarket support for it compared to the 231. Also, true SYE kits for them (not the hack and taps) cost about twice as much as the 231 kits due to either Tom Wood needing to machine your old output shaft and tail housing, or Iron Rock to make you completely new ones.