Twisty Posted July 13, 2006 Share Posted July 13, 2006 I bought my 88 MJ from a member on this board (BirchBomber). I read all of his old posts hoping to shed light on this issue. The issue is that R, 1-2, 3 work (i know that R and 1-2 do) but D won't. He said that it needed a new shift computer. I researched, and found that it was located under the passanger dash, and i looked and i found it. I pulled it out of my 1990XJ and went up to the MJ. to my relief this was missing from the MJ. I just wanted to be sure that this was infact the computer, so here are the pics. Then i moved my XJ, and D worked....but there was a ton of slippage somwhere. so i don't know if this is the right part. i didnt know where to put this in..so ill put it here. in a box of parts that he gave me there are about 5 of these boxes...some with red stickers and some with orange stickers. kinda peculiar i think. thanks. Link to comment Share on other sites More sharing options...
BrettM Posted July 14, 2006 Share Posted July 14, 2006 That is the Transmission Control Module, and if your MJ doesn't have one, it needs one. Without it you should be able to shift with the stick from 1st (1-2) to 3rd (3) to 4th (D). When you say there is a lot of slip in your XJ when you try driving it without the computer, I assume you are just putting it in Drive, in which case the transmission is in 4th without the computer, so yes, there will be LOTS of slip (bad idea). Link to comment Share on other sites More sharing options...
Twisty Posted July 14, 2006 Author Share Posted July 14, 2006 ok brett...thats super. yes i did have the XJ in drive. it moved but very slowly. then when i put it in 1-2 it moved just fine. like i said, the MJ works in 1-2, and R. ive never tried it in D or 3 though. i have the MJ on jackstands now...so i think while its up there ill fire it up and see if D works. thanks again brett. Link to comment Share on other sites More sharing options...
Twisty Posted July 15, 2006 Author Share Posted July 15, 2006 ok so tonight i put it 1-2 to get an idea of how fast the wheels spin in 1st. then i put it in d. the speedo went up to 15mph and spun hella fast. then i put in the TCM. eagerly i put it in d, and watched the wheels. they spun really fast and the speedo was at 15mph. keep in mind that this was with the TCM from my 1990 XJ. whats wrong here? also...i think that the guy b4 me messed with the NSS cause i can start in in R. what should i do next? Link to comment Share on other sites More sharing options...
Eagle Posted July 17, 2006 Share Posted July 17, 2006 The standard FSM diagnostic for the AW-4 tranny is to pull the fuse for the TCU and run it by shifting manually. You lose either first or second gear (don't recall which), but all other positions should function. I don't think you can get any sense of what it's doing when it's up in the air on jack stands. You need to get it on the ground so there's some resistance. Speaking of fuses -- if the MJ didn't have a TCU in it, and you installed a TCU from the parts XJ ... did you check to verify that you're getting power to the TCU? Whoever yanked the TCU might have also yanked the fuse ... Link to comment Share on other sites More sharing options...
BrettM Posted July 17, 2006 Share Posted July 17, 2006 Very simple, the transmission is not getting any shift signals from the TCU (if you even have one). Link to comment Share on other sites More sharing options...
Twisty Posted July 19, 2006 Author Share Posted July 19, 2006 ok...ive asked a guy at the local jeep club, and he gave me inmfo on what pins provide power. I'm going to test them with a multimeter to see of its getting power. Link to comment Share on other sites More sharing options...
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