auto trans not shifting

[mjbudd]

I bought a 87 jeep Comanche that has been converted from a manual to an auto trans and from a 2 wheel drive to a 4 wheel drive. When I got the truck the engine bay harness didn't have the plugs that go to the trans harness or the tcu. I went to a junk yard and pull all of the harness and tcu from an 88 Cherokee. I got the engine bay harness installed along with the tcu but my trans still won't shift on its own. I still have to manually shift it. I checked the fuses and everything is getting power. I adjusted the tps and rechecked the plugs and everything looks good. Am I missing something that anyone can help me out with? Any help would be greatly appreciated.

[ScottJeep]

Well... I don't have much experience with your situation based on the manual/auto and 2WD/4WD swap but I just 

thinking my first couple of questions are:

 

1. Do you have backup lights when the gear selector is in Reverse?

2. Can you start the truck in both Park and Neutral?

 

My other thought would be my manual MJ was 3:07 geared rear and my auto is a 3:55 which based on my reading is pretty 

normal.  Based also on other auto experience the autos usually want to kick into Overdrive ~45ish MPH. 

 

Other questions....

 

1.  Good tranny fluid color?

2.  Will it change into ANY gears or just certain ones?

 

Would highly advised downloading the transmission manual.  Should find it easily here via a search or looking around. 

Use the diagnostic portion.  Has saved me a couple of times when I had some issues with my XJ.  

[cruiser54]

I bought a 87 jeep Comanche that has been converted from a manual to an auto trans and from a 2 wheel drive to a 4 wheel drive. When I got the truck the engine bay harness didn't have the plugs that go to the trans harness or the tcu. I went to a junk yard and pull all of the harness and tcu from an 88 Cherokee. I got the engine bay harness installed along with the tcu but my trans still won't shift on its own. I still have to manually shift it. I checked the fuses and everything is getting power. I adjusted the tps and rechecked the plugs and everything looks good. Am I missing something that anyone can help me out with? Any help would be greatly appreciated.

Is the tCU getting power? 

[mjbudd]

Well... I don't have much experience with your situation based on the manual/auto and 2WD/4WD swap but I just

thinking my first couple of questions are:

 

1. Do you have backup lights when the gear selector is in Reverse?

2. Can you start the truck in both Park and Neutral?

 

My other thought would be my manual MJ was 3:07 geared rear and my auto is a 3:55 which based on my reading is pretty

normal. Based also on other auto experience the autos usually want to kick into Overdrive ~45ish MPH.

 

Other questions....

 

1. Good tranny fluid color?

2. Will it change into ANY gears or just certain ones?

 

Would highly advised downloading the transmission manual. Should find it easily here via a search or looking around.

Use the diagnostic portion. Has saved me a couple of times when I had some issues with my XJ.

I don't have any reverse lights. The trans fluid looks clean and red and it won't shift any gears by itself I have to manually shift it. The tcu fuse is good and is getting power. Trans fuse in the fuse block is good also

[ScottJeep]

Well the common issue for no reverse lights is the NSS switch. And one would think if major issues there major shifting issues would happen. 

 

My experience brings me back to the conversion.  On my current MJ there is a connector at the top of the brake pedal.  

This wiring indeed has an impact to shifting for me....but only over-drive. The other side of the wiring shown came out of the wiring harness down under

the heater, below the ECU. 

 

Did you find the AW4 manual?

 

http://www.pirate4x4.com/tech/billavista/PDFs/AW4_manual.PDF

 

Goggle can be an awesome tool but gets you LOTS of reading.  Just gotta keep digging. 

[mjbudd]

Well the common issue for no reverse lights is the NSS switch. And one would think if major issues there major shifting issues would happen.

 

My experience brings me back to the conversion. On my current MJ there is a connector at the top of the brake pedal.

This wiring indeed has an impact to shifting for me....but only over-drive. The other side of the wiring shown came out of the wiring harness down under

the heater, below the ECU.

 

Did you find the AW4 manual?

 

http://www.pirate4x4.com/tech/billavista/PDFs/AW4_manual.PDF

 

Goggle can be an awesome tool but gets you LOTS of reading. Just gotta keep digging.

I'll have to check into that plug and see if it is there. I got the cab harness from the xj to I just haven't installed it yet. Could that be the problem? Is the actual cab harness different from auto to manual? I did look into the manual and it doesn't really show anything about not shifting just harsh shifting or not downshifting but i will keep looking. Thanks for everyone's help if you can think of anything let me know

[gogmorgo]

I don't think the NSS would be causing your shifting issues. Before I cleaned it in my '91 (It was BAAAD... no reverse lights or starting in any gear without shorting the solenoid most of the time) I didn't have any shifting issues whatsoever. Also, if you look at the wiring diagrams for an '88, as found here, courtesy of Blue88Comanche, there are TCU inputs for Drive and 1-2, but not for third... my guess would be that has more to do with torque converter lockup or shift points than anything else.

But by all means go ahead and clean up the NSS, it's easy and won't hurt anything. Here's an excellent write-up. I ran a bead of RTV around the gasket before putting everything back together to try to help seal it a bit better.

[MJam86]

Could be solenoids

[sdougwilliams]

I have done the same thing your trying to do with my 86 Comanche XLS.  I pulled the old V-6 and installed a 4.0L with AW-4 automatic transmission and then converted from 2 to 4 wheel drive.

 

I replaced the wiring harnesses in the engine compartment with some off a 87 or 88 Cherokee with automatic transmission from a local salvage yard

 

You do need the wiring harness that goes from the transmission to the inside on the passenger side where the TCU is bolted up under the glove compartment.  There is a inline fuse there inside under the glove box which may be your problem.

 

Additionally there is some wiring you have to do to get the backup lights to work.  

 

In the little three wire connector shown in previous posts I remember connecting the Black-yellow wire to the Brown/Light Green wire in the same harness that connects to the ignition switch on top of the steering column.  I had to either do this to get the tachometer or backup lights working.  I am fuzzy on exactly what that solved.  

 

Additionally, the tan wire of this connector needs to go to the Power/Comfort switch you probably don't have in your dashboard.  That switch also needs connected to the transmission fuse, not to be mixed up with the inline fuse i mentioned earlier.  And it needs a good ground.  When power is applied to the tan wire this puts the transmission into Power mode versus comfort mode.    

 

Also check the transmission kick down cable which connects to the throttle body.  This is adjustable.  Just squeeze the adjuster and set it close as possible and it will set it self when you step on the throttle-Wide open.  

 

Hope this helps.