Hey guys. I just bought an 88 MJ, I6, auto, 231. It needs a little tlc here and there, but I am starting with the trans. The trans pulls good and shifts strong, but it is not shifting right. It will not down shift, when you take off it imediatly goes through the gears fast than the engine can keep up. By 30 mph its in 4th. It acts like an old carb engine trans that the kick down linkage has been taken off. And last, the power/comfort mode button seems to be dead. It doesnt do anything and the light in it doesnt come on when it is switched to power mode like it should. I just got it yesterday, so I have not even looked to see if it has a kick down linkage, but I would assume it is computer controlled. I thought I would throw it up on here first to see if it was somthing obvious to you guys experienced with the 88 AW4. I figure its probably a trans control module. I know some vehicles used to use a seperate computer for the transe, I didnt know if that is the case here.
Thanks for any thoughts!
Chad

 

Welcome.
Compliments on the courage buying something that runs like that...
Start with some basic stuff first. Renix is not my expertise, but some basic checks are general.
Check the ATF fluid and quality. If its all brown black, start draining and refilling. Repeat this with some driving in between, untill the ATF stays nice and red.

Try shifting it manually, to see if the shifting is normal. You can use this to discriminate between electrical versus mechanical issue with the trans.

The kickdown cable can be adjusted.

Just a basic start for things and simple stuff first: let us know what you find please.

 

The trans shifts just fine if shifted manually. It has good fluid and is full. That was one of my questions id if it even had a kick down cable or linkage. I know many of the newer computer controlled autos no longer have the kick down cable or linkage.
So I went out and looked, and it does have a kickdown cable which appeaers to be in tact and functioning.

 

Manually shifts fine....so the shifting issue is likely electrical - like solenoids.
Checked fuses already, also the TCM's ?( I keep forgetting who's got a nice pic of that, either CCKen or Cruiser; I'm sure one of them will chime in)

 

Fixed......throttle position sensor

 

Makes perfect sence. TPS is closely involved in shifting characteristics of the trans.
Thanks for getting back.

I understand OEM TPS are getting more difficult to come by. What brand did you put in?

 

Also make sure the 7.5 amp "trans" fuse in the fusebox isn't fried. If it is, before replacing it, do this:

Bypassing the Power/Comfort Switch on a Renix Jeep

Remove and unplug the switch. In the harness are 3 wires One has a stripe, one is tan, and the other black. Make a 4" jumper wire with a male spade at each end. Plug one end in the cavity for the tan wire and the other in the cavity for the striped wire and you'll be in permanent Power mode. Stuff the harness back in and reinstall the switch for looks.

 

I think its a bosch tps, but I didn't pay much attention. THey had it in stock at the local parts house.
The trans fuse and power button are functioning well. I had to clean up a few grounds to get the power switch to work properly.

 

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