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'89 Cherokee 2wd AW4 issues...

T

thedude

NAXJA Forum User
Location
Hopkinsville,Ky
Hello all,
This is my first post on here. I've used the search option and couldn't find anyone having the exact same issues as me so I don't know if its something that could be common.

The transmission and everything works great except it won't shift. It wants to start out in 4th gear. I can manually shift it into 1-2 but it will only use 1st gear and not 2nd gear. The gears hold very firm and never slip. This jeep has 243k on it, I just got it a few weeks ago and this problem only occurred recently within the past week or two.

Shift solenoids(I'm told thats most likely not it)*havn't gone to purchase another volt meter*
governor in tail housing possibly stuck?
TCU failed?

Really appreciate any respones or resources you guys can give me. Right now I have the pan dropped and it had the usual gray sediment with no abnormal worn particles. The trans was rebuilt sometime before 200k by the previous owner.

Thanks! Contact me on AIM or yahoo if you have any further suggestions.

AIM: ChronoMonkey
Yahoo: Thedudescf
 
That sounds like the computer is unplugged to me....if you're sure it's plugged in, you might try another TCU.

I don't think it's your speed sensor as I left my speed sensor unplugged after doing and SYE and it didn't phase the shifting in the slightest, I just didn't have a speedometer. TPS would be another likely possibility, I think you can check that with an ohm meter tho.

AS for the TCU I don't know what to tell you, if its completely non responsive I don't know a way to test it. On a good note tho, if it is your TCU and you can't find one cheap, I was recently chasing a problem with my tranny and came down to my TCU....I found a bitchin deal on one, but before I got it in the mail, i found my problem was actually the brake sensor. Consequently I have a TCU sitting right here atm. You might be able to find one cheap locally, but if not I'll check this one to make sure it actually works and if so, I'll part with it for the $22 I paid plus shipping.

But first I'd make sure that the plug didn't just come loose somehow...it may just need to be pluggd back in

EDIT: Oh, or a fuse....yep, that'd do it too :D
 
SanDiegoXJ said:
That sounds like the computer is unplugged to me....if you're sure it's plugged in, you might try another TCU.

I don't think it's your speed sensor as I left my speed sensor unplugged after doing and SYE and it didn't phase the shifting in the slightest, I just didn't have a speedometer. TPS would be another likely possibility, I think you can check that with an ohm meter tho.

AS for the TCU I don't know what to tell you, if its completely non responsive I don't know a way to test it. On a good note tho, if it is your TCU and you can't find one cheap, I was recently chasing a problem with my tranny and came down to my TCU....I found a bitchin deal on one, but before I got it in the mail, i found my problem was actually the brake sensor. Consequently I have a TCU sitting right here atm. You might be able to find one cheap locally, but if not I'll check this one to make sure it actually works and if so, I'll part with it for the $22 I paid plus shipping.

But first I'd make sure that the plug didn't just come loose somehow...it may just need to be pluggd back in
Click to expand...

Thanks a ton man, check and make for certain it works. First tomorrow when its not so chilly outside I'm going to start doing what I dread the most... chasing wires.

Before that I'll put the pan/filter back on the trans, right now its still apart because it got dark.
 
On second thought I'm a curious bastard and might just finish up putting it all together in the dark just to see if something came loose from the TCU, I checked all fuses and they are good. If there's a fuse under the hood I havn't checked it cause I don't know which it would be.

This all hit me directly after I got all the heating/cooling issues solved with this awesome closed cooling system, rear main seal leak, head gasket/water jacket leak, power steering pump leak(almost got fixed now), valve cover gasket leak, thermostate housing leak, crankcase vent tube pushing the coolant that was in the oil into the airbox and soaking the filter... then this.

Paid 400 bones for it and had my work cut out for me. 243k on the clock.
 
There is at least one more if not two more wiring harness connections that could be loose, or corroded, under the hood in addition to checking the TCU wiring harness conections under the steering column in the cabin. One is a second connection to the TPS. The second is near the firewall on the passenger side connecting something on the the transmission to the wiring harness I think.

Mike McGinness
South Houston, Tx
 
Ecomike said:
There is at least one more if not two more wiring harness connections that could be loose, or corroded, under the hood in addition to checking the TCU wiring harness conections under the steering column in the cabin. One is a second connection to the TPS. The second is near the firewall on the passenger side connecting something on the the transmission to the wiring harness I think.

Mike McGinness
South Houston, Tx
Click to expand...

You wouldn't happen to have a link to a diagram? I've looked through the haynes manual and can't find anything that even mentions the TCU. I'll look around and see if I could have possibly gotten some water in one of those connections near the firewall or possibly messed with something on the steering column.
 
Hey I know it was mentioned before but that fuse for the TCU is under the passenger dash right next to the TCU it's usually the problem with 4th gear starts. I know 'cause I half to pull mine out after driving about 45min to get my AW4 to shift:doh: It will only shift when U manually shift and only go up to 3rd. 1-2 = 1st, D = 2nd and OD = 3rd. Check that fuse then search for AW4 problem on this forum and you will find further instructions if that doesn't work.
 
thedude said:
You wouldn't happen to have a link to a diagram? I've looked through the haynes manual and can't find anything that even mentions the TCU. I'll look around and see if I could have possibly gotten some water in one of those connections near the firewall or possibly messed with something on the steering column.
Click to expand...

What you really need is a picture of it to help you locate it first. The Wiring diagrams I have won't do that. All the old jeep connectors are bad about corrosion and loose contacts. Following the wiring from the TPS (Throttle Position Sensor) to the transmision and then from the transmission back, all under the hood. Then check the TCU connections under the steering column in front of the brake pedel.

Mike McGinness
South Houston, TX
 
SanDiegoXJ said:
anyone know if a '95 aw-4 comp will work in a '89?
Click to expand...

I believe it will, but you will have to modify the wiring harness connector by shaving off the keying ridges. Five minute job with an exacto knife or even quicker with a dremel tool.

I would go get a meter and verify that you have power to the TCU connector, the resistance across the solenoids, and then check that you get power to solenoid 1 (I think thats right) when you have the ignition on and the stick in Park, Drive, Neutral, or Reverse.
 
thedude said:
You wouldn't happen to have a link to a diagram? I've looked through the haynes manual and can't find anything that even mentions the TCU. I'll look around and see if I could have possibly gotten some water in one of those connections near the firewall or possibly messed with something on the steering column.
Click to expand...


Here's a link to the AW4 manual. Scroll down to the "transmissions" section.

http://www.pirate4x4.com/tech/billavista/PDFs/index.html
 
Whew just woke up, I went out and looked at it some last night, but it was too dark and my flashlight went dead so I'll take that as notice to go to sleep lol.

Going to work on it now. Thanks for all the input fella's.
 
Got the filter/pan/fluid all back in the trans and it still does the same thing, checked the fuse running to the TCU, the fuse thats in the fuse box, and they are good, can only find unmarked relays under the hood and there is no diagram of which is which in my haynes manual.

When I unplug the TCU it acts the exact same as if it were plugged up.

Going to try to contact some junkyards today and tomorrow and see if I can find one locally just to try out on mine. I'll keep you guys updated and thanks for all the help.
 
thedude said:
I decided to ask before I disassembled it, but do you guys think it could be that my neutral safety switch needs to be taken off/cleaned?
Click to expand...

No. There is no way the NSS could cause you to start in 4th. But while you're crawling under there, follow the wiring harness up from the drivers side of the tranny, up and over the bellhousing to the passenger side of the firewall. There is a square connector just below the heater core piping for the solenoids and sensors. The other identical, but different color is the connector from the NSS. One is black and the other grey, just can't remember which is which.

Honestly, the easiest test at this point is to probe the TCU connector and see if it's got power and applying power to the solenoid with ign on and parked. Then pull the connector off the TCU and measure resistence through the solenoids. That will verify the TCU and the wiring.
 
*Update*

TCU box was fried, buddy of mine let me borrow one he keeps at his shop for diagnostics.

Went through 2 junkyards today who both claimed to have a TCU and neither did. Tuesday after Christmas one last junkyard in the area who claims to PHYSICALLY have his hands on a TCU box.

Much Thanks for all ya'lls help I'm sure I'll be needing it again with this jeep.
 
Congrats on solving it. I am surprised that the TCU was actually bad. I think yours is only the fifth one I've heard of actually being bad (confirmed by swapping in a good unit or checking the solenoid outputs with a meter). Usually it's power to the TCU or a bad solenoid.
 
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