Modified Aisin-Warner AW4 Tech

[MachineMan]

Your '90 mosty likely is a 21spline and the '98 is a 23spline.

You can make it work by changing the T-case input gear to 23 spline. That's what I did to fit a '95 into my '90. Im not sure about the electrical connectors compatibilty on the '98.
T-Case input gear Write up: http://www.4x4trailhunters.com/article.php?id=20

 

[brendon800]

At the begining of this post it says 90+ are 23 spline...I haven't taken my trans out yet, but hoping it IS 23. The electronic stuff...God help me there. Hopefully a guru can help me out with all this.

 

[HTeK]

My '90 is a 21 spline. Based on my research, I beleive 91 was the changeover year... but I have heard that in the 90/91 years there are no certainties.

-jm

 

[brendon800]

Great, I have NO idea on how to pull this transmission out, besides being on disability(not really allowed to work on this stuff). So, it's a whole lot of hit and miss going on here, and spending a WHOLE lot of money to miss every time. Wonder how much that would cost to change the thing MachineMan had said about, and how hard it would be to do.

 

[brendon800]

So, is there any hope that I might have a 23 spline transmission? And how hard is it to take out my old transmission? It looks like the exhaust is in the way of dropping the bell-housing, then there's the cross-member below the TC, and I cant even see the bolts on the top of the bell-housing, let alone take them out.

 

[MachineMan]

If your rig is a '90, you most likely have a 21 spline trans. You will have to remove the exhaust. Also you will drop the tranny and transfer case at the same time. Remove the access plate on the bell housing bottom and take out the 4 flywheel to torque converter bolts. Oh, don't forget those two E12 torx bolts on top of the bell houseing and to unplug your CPS. The T-case linkage is also not so fun. Its not a hard job but more of a pain-in-the-ass job. If your rig is lifted it will be much easier and renting a tranny jack with tilt helps alot.

 

[Yucca-Man]

Look at all them pretty colors...

That's the jist of it right there...I just got mine reinstalled and fired up this evening; I have to recalibrate the shifter and I should be on the road now.

Keep track of all your small bolts and nuts. Replace those PITA E12 bolts with...umm...I posted it a week or so ago. The tranny and t-case can come down as one piece if your tranny jack will securely hold them both. Otherwise, there are six studs coming off the front of the t-case that will need to be removed from the tranny adapter so you can pull the t-case.

 

[5-90]

Replace those PITA E12 bolts with...umm...I posted it a week or so ago.

As I recall, they're 3/8"-16x1.75". Hex heads OK, socket heads with hardened washers OK.

5-90

 

[brendon800]

Any thoughts on the electrical aspect of this transmission? Say I go ahead, and replace that input gear to a 23 spline, will the transmission then work okay? I mean, will the plugs from the 98 AW4 work with a 1990 Cherokee? Oh, I'm also seeing a lot of NP231's that are 21 spline, but they are from 4cyl vehicles, the NP231's from 6Cyl models seem to be 23 spline that seem to include the 1990. Of course this is from eBay, so God only knows what he's selling, but he's got all sorts of transfer cases for 6cyl, 4cyl models. But either way, it seems if I go with MachineMan's advice, and change out that gear, it will at least bolt up, now I need to find out if the electronical aspect will be okay. You guys have been MORE than helpful, and I thank you all so much!
-Mike-

 

[BrettM]

Any thoughts on the electrical aspect of this transmission? Say I go ahead, and replace that input gear to a 23 spline, will the transmission then work okay? I mean, will the plugs from the 98 AW4 work with a 1990 Cherokee? Oh, I'm also seeing a lot of NP231's that are 21 spline, but they are from 4cyl vehicles, the NP231's from 6Cyl models seem to be 23 spline that seem to include the 1990. Of course this is from eBay, so God only knows what he's selling, but he's got all sorts of transfer cases for 6cyl, 4cyl models. But either way, it seems if I go with MachineMan's advice, and change out that gear, it will at least bolt up, now I need to find out if the electronical aspect will be okay. You guys have been MORE than helpful, and I thank you all so much!
-Mike-

the electronics will not plug right together. 87-96 are plug'n'play, 97+ are different. With some splicing, it may work. I've heard from some that had to swap the speed sensor, and some that did not have to.

 

[brendon800]

Well, looks like this is way more than I'd bargained for. I'll most likely be putting this '98 AW4 up for sale. I just figured if it was an AW4, it'd work...and for $200.00 as opposed to the 1025 for a new one on eBay, I'd go ahead with it. Only 50K miles on this one seemed like the way to go. My other one quit on me, was shifting eratically, then just quit shifting, seems it goes into 2nd and 3rd, but winds out HORRIBLE bad before it shifts...Then it doesn't seem to want to shift at all afterwards. Hehe, the nice thing is...It's got TONS of torque right now, just can't drive it any further than a couple miles...Any suggestions?

 

[Gojeep]

Speed sensor is different so needs to be swapped with the older one.

 

[fuzzydog]

bump so I can find it and read it more thoroughly when I get home tonight

 

[FitchVA]

i'm pretty sure non-paying members can subscribe to threads to do the same purpose. look under the drop-down menu under "Thread Tools" in the upper right region of the page.

 

[fuzzydog]

...... non-paying members .......

OUCH! I don't know if you meant it that way...but thanks. I should be a paying member. This is one of my favorite sites on the net and it has saved me time and money, as well as just plain given me great ideas and inspiration for my XJ build. I will become a paying member today.

 

[FitchVA]

simmah down bud, i was only stating that because some features are sometimes cut off and reserved for forum supporters to use. that's all.

 

[tealcherokee]

this thread is old as hell, but, i dont care. its linked to alot, and is full of wrong information.

ALL cherokees with an AW4 (1987-2001) have a TCU. 87-96 are behind the passangers side dash.

97-01 TCU's are located under the steering column. the myth that the pcm controls the AW4 in 97-01 xj's is completely false.

also, the 21 spline aw4's overdrive is 0.79:1
23 spline overdrive is 0.75:1

 

[Root Moose]

the myth that the pcm controls the AW4 in 97-01 xj's is completely false.

This is correct. Post #1 in this thread is not as precise as it should be in regard to this point.

What it should read is: the transmission PCM/ECU is a separate unit that talks to the engine PCM/ECU. This is why when you try to do the modifications that hold the TCC or manually select gears you will end up with a MIL on the dash.

 

[kastein]

That's not even quite precise - it's closer though. What it should read is:
the Transmission Control Unit (TCU) is a separate unit that controls the transmission, and communicates with the Engine Control Unit (ECU) via the CCD bus. Its design was upgraded and it was made more intelligent on model years 97 and later. This is why simply overriding the solenoid drives to control the transmission manually will result in a Check Engine Light on these model years.

PS - tbburg started a thread about his experiences with a mod kit which keeps the 97 and later model years from throwing a CEL when manually switching gears 1/2, lawsoncl and I have also added some of our insight concerning the mod's workings. It's an excellent kit apparently. See http://naxja.org/forum/showthread.php?t=1010278 for more info

 

[johnfrog]

My little bro ran my jeep out of tranny fluid (and then until it wouldn't move anymore) I pulled it apart and found a broken gear inside the pump. What's the chances of this being the only issue? And I can't find a replacement gear anywhere. Is there a parts store for this gear that I am missing? 125kmiles on jeep.