rawk krawler

Hey guys I bought a 99 wj with 4.0/ 42re / np242 and it does not want to shift past 2nd, also she bucks hard in reverse, repetitively. I popped the pan and found the piece of a snap ring and enough metal on the magnet to make you think it was a damn troll lol. I did replace the sensor and module for $h17$ and giggles but it did nothing, no surprise, I also hear a whirring noise from the back, pretty subtle, almost like the rear end or outer bearing is worm, but for now we're going to assume it's the overdrive on the 42re. Anyways, long story short a junkyard not to far away has a few 42re transmissions in various wj's and I'm curious which ones will swap directly over?? Thanks in advance!

dave1123

Any WJ 4.0 has the 42re that you need. ('99-'04) The difference between this one and the older ones is they put the vehicle speed sensor inside the trans instead of on the t/case.

Be aware that you can remove the O/D section without removing the transmission. There is a good write-up on this page you should read. It's an update of a 3 year old post.

rawk krawler

I know they can be pulled separately but pick n pull has no listing for an overdrive so I figure they'll charge me for a full transmission. Atop that I had a lot of material on the magnet, more than I've seen pictures of, and my oil was about as clean as old engine oil. Thank you for the info I'll pull one today.

rawk krawler

As far as researching prices and compatibility, all 42re transmission interchange, they changed the internal wiring harness, and external plugs remained the same. Both wj and zj have one output sensor on the rear of the tranny. And the older one will cost 1/3 at a junkyard, is this correct? My pricing is due to wj's being in picknpull premier yards.

dave1123

Okay, the ZJ's have the speed sensor in the t/case. The WJ's are inside the transmission, I'VE BEEN TOLD! I really haven't checked that out myself, so maybe the info is bogus, IDK.

rawk krawler

Well I appreciate the help man, I'll be trying to pull one tomorrow and I'll report on my findings and maybe do a little write up for future reference.

gpXJ

This is true. The ZJ used a speed sensor in the tail housing of the transfer case, just like the XJ. The WJ does not have that speed sensor in the transfer case, as it is inside the trans.

rawk krawler

Where inside? All I see is the same two sensors, and it has 2 plugs on it same as my 99. So far the only difference I found is the filter

rawk krawler

Isn't the speed sensor from xj case just for speedometer? The wj has speed o sensors in rear I believe.
4 bolts left and it was pulled, ran out of time haha, guess an hour wasn't enough time

dave1123

Your '99 would have the internal sensor.

rawk krawler

What is the internal sensor though?

dave1123

IDK. I haven't had mine long enough to get into it. My manual is for the 42RE-A500SE. Okay, I just checked. It's screwed into the passenger's side of the overdrive case near the top. It monitors the output shaft speed by counting the teeth on the park lock ring and sends the info to the TCM, which on the WJ, is part of the PCM. BUT, according to the manual, the TCM compares this signal with the VSS sensor signal on the t/case. All this gets confusing. Maybe on the WJ, it doesn't need a VSS, IDK.