Okay, so I just replaced my transmission in my 98 Jeep Grand Cherokee. The transmission was a 42re, the one i replaced it with was from a 93 grand. Now im told that one was eletrical and the other was mechanical or hydraulic im not sure.. but the two trannys looked identical, before I made the switch i had to replace a censor... this was the one under the shifter which I believe is the Neutral Saftey Switch... although im not sure, the reason i had to change it was becuase the connectors were different, they were both three pronged but had a different plastic casing. Anyway when i pulled both sensors out they looked identical in length shape colour etc.. so i didnt think anything of it. Well now I got everything back together and the Jeep wont start when i turn the key, Battery is fine and so is the starter. I can start the jeep by touching the two bolts on the starter together with a screw driver and the jeep runs fine.. but i still cant start it with the key. I tried starting in Neutral and park, still nothing, tried playing around with my shifter and nothing.. It sound like a faulty neutral saftey switch to me.. but I cant be certain, whats your thoughts and I am also wondering if i missed a step or somethin.. is there a difference in the two transmissions that would cause this problem? Im pretty stumped on this one..
I have a question, does it just struggle to turn over, or does it just not even do anything but go straight to Aux? Because I'm having a problem with my ZJ not starting, but it's because of the security "Flash to pass" crap. I had to click unlock on my fob to pass the starting codes to pass security, but then my fob stopped working all of a sudden at a gas station. My only suggestion would be to check the security system first off. But that's only if it doesn't even turn over.
I am not sure what tools you have, but just a voltmeter can tell you a lot. If you are not sure on the NSS then get out a volt meter and locate the NSS circuit and follow it until you cant find a signal. If you have a signal, then I would suspect your ignition switch. Same deal, with a volt meter you should be able to check it and see if you are getting 12v to the starter relay.
I use a PowerProbe. It is like $100 and you can do so so so many awesome things with it, that help diagnose these sort of issues.
But at minimum you will need a volt meter and a few wiring diagrams. You really just can't go throwing parts at something like this.
I would have at least of checked the casting numbers on the transmission, before I did a swap. I know these Jeeps are really really picky as far as what parts can actually interchange.
--- 1998 ZJ 5.9 Limited - 4" lift, 31 x 10.50 15, Jet chip, Kenwood Excelon everything, current DD
--- 1996 ZJ Laredo - Parts parts and more parts
--- 1993 ZJ Laredo - 4.0 Bone stock for now (New to me)
Also i dont think it is the ignition switch because it was all working fine before the swap. I just found out that the transmissions were the same just one is older. The only difference was that nss and the torque converter bolt pattern but thats okay