Changed Engine now AW4 tranny wont shift out of first!!!!!!!!

[90xjjoe]

Ok So here is the story... I have a 90 jeep cherokee that needed a new motor so i swapped out motor with a 4.0 from a 88 cherokee that was manual. The motor runs great now but now my transmission wont shift past first gear when put into drive. I have changed the fluid and filter, crank sensor cleaned cannon plugs by the dipstick. I have exhausted my knowledge. I am pretty sure its electrical based on the fact that i found the trans fuse under the steering wheel blown, changed the fuse and no change. please help!!!!

[Brasscatz]

Did you hook up your kickdown cable? It tells the transmission when to shift

Sent from my Samsung Galaxy S4 because my microwave couldn't do it

[90xjjoe]

Yeah I have checked and tripled checked all the connectors and cables. I have even dropped the transmission again to ensure that the torque converter was seated properly. I am going to attempt to check the tps with a multimeter today and make sure that it is putting out the proper reading. Ill let you know what I find.

[4.3LXJ]

What year transmission and TCU did you use?

[90xjjoe]

Ok so I changed the tps and no change. It was the same transmission just an engine out of an 88 xj. the tcu is the same tcu however i did pull the fuse on the tcu and was able to shift manually. any ideas?

[bluedragon436]

Did you maybe short out the TCU when you were swapping out the engine, like possibly leaving the battery hooked up or something and hit the starter + line or something that might have shorted the TCU?? Do you know of anyone you can borrow a TCU from just to throw it in and see if it'll work the issue out for you??

[4.3LXJ]

I think your TCU is shot. It is apparently sending current to the solenoids responsible for electronically selecting first gear and won't shift. You know the tranny works since you can shift it manually. I think it is time for a new TCU. However, check that wiring harness for abrasions and any pinching. It is possible that you have pinched it when installing your engine

[JENSSEN]

I had a similar issue about 10 years ago, swapped the tranny ecm, checked all the tranny solenoids through the harness even replaced them and never cured it, but if \i pulled the fuse under the glove box I could shift manually fine,..

never found the cause, swapped in a new tranny and all was good

[90xjjoe]

Ok thanks for the ideas guys I am going to try a tcu from a buddies jeep today. fingers crossed it fixes the problem ill let everyone know how it goes later today.

Oh just out of curiosity has anyone ever heard of a input speed sensor take a crap. Not the output cable the input sensor on the trans itself? Hopefully this wont matter if i change the tcu out but just a thought.

once again thanks for the help!

[bluedragon436]

Glad you got a buddy that'll help you out... and hope that the TCU will take care of your issue... Look forward to hearing good news!!

[JENSSEN]

Ok thanks for the ideas guys I am going to try a tcu from a buddies jeep today. fingers crossed it fixes the problem ill let everyone know how it goes later today.

Oh just out of curiosity has anyone ever heard of a input speed sensor take a crap. Not the output cable the input sensor on the trans itself? Hopefully this wont matter if i change the tcu out but just a thought.

once again thanks for the help!

I will look into the input speed sensor, never Checked that on mine,..

Interesting!

[4.3LXJ]

Ok thanks for the ideas guys I am going to try a tcu from a buddies jeep today. fingers crossed it fixes the problem ill let everyone know how it goes later today.

Oh just out of curiosity has anyone ever heard of a input speed sensor take a crap. Not the output cable the input sensor on the trans itself? Hopefully this wont matter if i change the tcu out but just a thought.

once again thanks for the help!

Any sensor can fail. But that one would definitely affect shifting

[Black89]

Just out of curiosity you said the 88 engine was in front of a manual tranny. Did you use your original Intake and TB or the 88's? If you used the 88's that means the TB has only the one plug TPS sensor. The Auto's have the two plug. One for throttle adjustment and the other goes to the TCU. Other things to check is the ground for the TCU/TPS down next to the dip stick. I actually just had an issue with my 89' where it was locking the TC up in first and second. It felt like a manual tranny. I after a week of testing and adjusting I finally put in my spare TCU and bang solved the problem.

Black89

[90xjjoe]

ok so here is the latest i threw in another tcu and nothing changed so im leaning towards the input speed sensor. i have been in the middle of a motor swap on another truck so havent had time to get it changed out so ill be doing that today and ill let everyone know how it goes!:bang::bang::bang: