Hi, I'm new to this forum and am looking for some help. My 97 ZJ lasted 180k miles with the original 42re tranny. Last month it started slipping in 3rd and 4th gear, then would just shift from 1st to 2nd and that was it. Reverse worked, but shuddered and slipped. At that point I knew it was time to get a new transmission. Oh BTW my jeep is two wheel drive. Needing to replace the transmission I figured it was the perfect time to convert to 4 wheel. My finances limited me to do it on a budget, and after pricing out everything I would save 800 dollars over buying a rebuilt tranny. So I bought a 42RE four wheel model from a WJ with 80k miles and clean fluid for 200. A NP249 T/case from a 95 ZJ. (not sure of milege) with clean fluid, for 100. Have not yet bought the front axle. 3 weeks ago I started the build process. Mating the tranny to the t/case, I learned that the tranny output shaft was different in a WJ from a ZJ. No big deal, just bought an output shaft from a ZJ off ebay for 50 dollars. I then removed the overdrive unit from the WJ 42re and swapped the output shaft. Reassembled tranny with new filter and adjusted the bands. After that everything mated together perfectly (reassembled with new seals). Installed WJ tranny and t/case in jeep. Went to put up cross member realized tranny mount was different, solved that problem by making a mount. (didn't cost anything) Filled transmission with ATF 4 and t/case with Dexron 6. Went to hook up shifter linkage realized shifter stud arm was different, installed original shifter arm, problem solved. Started engine ran through the PRNDL got up to temp, topped off fluids. Overdrive off light on dash was illuminated. Road tested 1st, 2nd, and 3rd went perfectly but no overdrive. Used scanner found 2 codes p0783 and p0713. Replaced 3-4 solenoid and tcc solenoid, P0783 was gone. bought new fluid temp sensor and installed. (ZJ and WJ governor pressure/temp sensors are different). I cleared the code (p0713) but it can right back and didn't clear. I measured the resistance of the sensors and learned the ZJ temp sensor operated at around 1k ohms and the WJ sensor operated at around 2k ohms. (that's why it said it was hot all the time hahaha) As temp got hotter, resistance increased. Solved that problem by installing a 1k resistor in parallel in the signal and sensor ground circuit. Now I have no codes, the OD switch on dash can be turned on and off. but no Overdrive. I have checked all the fuses and relays that control OD that I'm aware of looking at all data. Hopefully someone has an idea.
Putting that 1k in parallel with the thermistor is not going to work properly.
The thermistor is 1k at room temp. I don't know what it should read at 260*, but it will never reach the needed resistance in order to automatically protect the trans from over heating with that 1k ohm in there. It could also be showing the PCM that it's not getting up to temp and allowing it to engage the over drive.
Also you shouldn't drive that 249 with the front shaft out, it will burn the VC out.
Thanks JS97ZJ, I didnt think the VC would blow out. Ill limit the driving. I was thinking that at room temp the ZJ fluid temp sensor is reading .997K Ohms and the WJ fluid temp sensor is reading 1.997K Ohms. So putting in the resistor knocked the resistance down to a proper level that the computer will like, and the fluid temp sensor is still functioning as a thermister. Maybe I'm wrong.
I wasn't aware that there was a difference between the two.m.
He does say he's got the 95 249.
Do you know if the thermistor in the WJ (42re) is the same type bolt on part as in the ZJ?
I've never had it apart so I don't know if he can some how remove the thermistor and do a swap. Or stick the ZJ sensor in an oven and get an ohm reading so he can make a swap with new replacement from an online electronic store.
From what I remember reading a while ago, was that the thermistor was mounted in the path of the transmission fluid flow so it can monitor when it warm enough to engage OD (50*) and when to disengage (260*) ?????