Everything you ever wanted to know about the AW4

Hello friends, I come to this forum on this topic to see if you can help me solve my case. I have a 1998 JEEP TJ I installed a 1989 cherokee xj transmission with a 96 transmission computer, we made certain adjustments so that the car would change in "D" is automatic transmission. My car works wonderfully, but I got a code that is P1698, it says there is no communication in the transmission computer, can someone help me?:huh:

PS: I'm from Mexico

JonaMarquez said:

Hello friends, I come to this forum on this topic to see if you can help me solve my case. I have a 1998 JEEP TJ I installed a 1989 cherokee xj transmission with a 96 transmission computer, we made certain adjustments so that the car would change in "D" is automatic transmission. My car works wonderfully, but I got a code that is P1698, it says there is no communication in the transmission computer, can someone help me?:huh:

PS: I'm from Mexico

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What transmission computer are you using? A 1998 TJ will not communicate with a 1989 transmission computer.

He's using a 96 computer, but that's still the problem. A 96 computer won't work on a 98 jeep if they are like xjs. And it's been covered in this thread that a pre 98 trans is pretty much impossible to get to work in a post 98 jeep.

Ah. I wasn't sure if he was using the TJ or XJ trans computer. The 89 trans should work with the 96 trans computer. It's just the 96 trans computer doesn't communicate properly with the TJs computer. Not surprising, or even a problem aside from throwing a code.

lawsoncl said:

Ah. I wasn't sure if he was using the TJ or XJ trans computer. The 89 trans should work with the 96 trans computer. It's just the 96 trans computer doesn't communicate properly with the TJs computer. Not surprising, or even a problem aside from throwing a code.

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Agreed. I think this is a code to ignore, given the circumstances. A TJ ECU isn't going to expect any TCU at all since the TJ 3 speeds are run by the ECU (it's technically a PCM on those models...) And the 96 XJ TCU probably won't be telling the TJ PCM what it wants to hear anyways. As long as everything seems to work, ignore the code.

kastein said:

Agreed. I think this is a code to ignore, given the circumstances. A TJ ECU isn't going to expect any TCU at all since the TJ 3 speeds are run by the ECU (it's technically a PCM on those models...) And the 96 XJ TCU probably won't be telling the TJ PCM what it wants to hear anyways. As long as everything seems to work, ignore the code.

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I have a 1989 cherokee xj transmission in my jeep tj, it is not the original 3-speed, it is the 4-speed automatic.

JonaMarquez said:

I have a 1989 cherokee xj transmission in my jeep tj, it is not the original 3-speed, it is the 4-speed automatic.

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I have a 1989 cherokee xj transmission in my jeep tj, it is not the original 3-speed, it is the 4-speed automatic.

"I wrote sorry in Spanish."

My jeep walks perfectly, it makes smooth changes, we even installed a button to put the OVERDRIVE on it and it works great, you accelerate and the car responds very strongly, but the check engine is always on and that bothers me hahaha. Only that it throws me the code P1698, I have a 1998 MOTOR COMPUTER, A 96 TRANSMISSION COMPUTER AND A 1989 CHEROKEE XJ TRANSMISSION. Sorry for the capital letters.

Last thing to add I am doing the post wrong I am adapting to the forum, the engine computer is from cherokee xj 1998 not the original from jeep tj.

Ohhhh that makes a big difference. I didn't realize you used the ECU from the XJ as well.

Make sure the two CCD bus wires connect to both the ECU and the TCU and the problem should go away. They are the twisted pair ones - I seem to recall one is white+black and the other is... Purple+brown I think? It's been a while since I looked.

kastein said:

Ohhhh that makes a big difference. I didn't realize you used the ECU from the XJ as well.

Make sure the two CCD bus wires connect to both the ECU and the TCU and the problem should go away. They are the twisted pair ones - I seem to recall one is white+black and the other is... Purple+brown I think? It's been a while since I looked.

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I have photos of the transmission connector.

https://ibb.co/SR1Vtrj
https://ibb.co/ZSdMX5D

kastein said:

Ohhhh that makes a big difference. I didn't realize you used the ECU from the XJ as well.

Make sure the two CCD bus wires connect to both the ECU and the TCU and the problem should go away. They are the twisted pair ones - I seem to recall one is white+black and the other is... Purple+brown I think? It's been a while since I looked.

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Apparently the harness I have is from the same cherokee xj 1989 but if the transmission computer is 96, which pin should I connect to the engine computer? We have connected the D2 to the TPS signal of the engine computer since in the diagram of the xj 1989 it says that haha but we are certainly bad and despite that the car works wonderfully, but I would like to turn off the check engine.

Agreen said:

It's 27 spline

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So cutting the shaft on the 2wd wouldn't work???

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Nope. At least not unless you make tcase mods too. As an experiment last summer I slid a 27 spline np241c front half I had lying around onto my old 2wd 88 AW4 output shaft, it fit perfectly at least on the slip yoke section. I haven't cut it down to try it on the section that would be in use with a 4wd extension housing though so I can't tell you for sure there. I also test fit my 2wd 88 AW4 rear driveshaft slip yoke on the output shaft of a 27 spline 700r4 (alright, it wasn't a test fit... I needed a plug for the trans in my wife's daily driver so I could pull it to replace the flexplate without dumping fluid everywhere, and had the aw4 yoke handy) and it fit fine. So yes, at least some years of 2wd AW4 are 27 spline.

To make a Jeep np231 fit that, you would have to swap the input gear to the 27 spline one from the correct year of Chevy np231/241. Make sure you stay on the correct side of the mid 94 planetary gearset tooth profile change. And I can't even guarantee that it'll fit the cut down 27 spline output... If you go back to the page you quoted that Agreen post from you'll see a pic near the top that clearly shows a step in the spline OD.

Unclewolverine said:

He's using a 96 computer, but that's still the problem. A 96 computer won't work on a 98 jeep if they are like xjs. And it's been covered in this thread that a pre 98 trans is pretty much impossible to get to work in a post 98 jeep.

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Indeed, I could write a dissertation on the difficulties in expecting a early AW4 to work with a later model XJ. Once I THOUGHT I had reached success and drove my XJ for months, it began to set code P0700 -- this despite the fact that the jeep runs and shifts perfectly, including the TC lockup. And does so with a '98 AW4 with input and output shaft speed sensors.

When I extinguish the check engine light with a scanner, if I keep the shifter in the '3' position it will drive for weeks w/o setting the code or lighting the light. (of course, with the shifter in that position, the TC won't lock up.)

If however, I drive with the shifter in the 'D' position, after about ten miles or so, the CE light illuminates. But the XJ Jeep will run and shift like a new one -- including TC lock up. In fact I'll be taking it on a 300 mile trip this W/E pulling a jet ski. And I'm pretty sure that the CE light will keep me company.

Changing the TCM, all three solenoids, as well as the wiring harness that runs between the solenoids and the firewall made no difference.

It's a compelling case for Car Talk's short piece of black tape over the light. Unless, of course, one of you guys can come up with a magic bullet.

I have 96 xj
What input automatic trans beside kickdown cable and tcu
I just swap manual trans to automatic and seem not increase gear
Thanks

The transmission computer uses the throttle position sensor and the output speed sensor to determine when to shift.

To update this topic, I just finished installing a 99 AW4 into my Renix Comanche. All I had to do was swap the reluctor for the OSS, and the extension housing from the old 21 spline trans. The newer trans output shaft has two snap ring grooves. The inner groove is in the exact location for the older 1 PPR reluctor. The extension housing from the 21 spline trans keeps the correct sensor location and mounting. I also swapped the entire wire harness and NSS from the old trans. Wire harness is super easy. Just take the oil pan off and unclip the three solenoid plugs, and take it out. Don't even have to mess with the valve body. Still using the renix era TCU, and everything works perfectly. As a side note, if you are going to keep the renix intake and throttlebody, swap out the TV cable while you have the pan off. That's easy to do as well.
Hope this helps, as it was difficult to find anyone that has done the swap with a follow up confirming it actually worked.


-Dan

Loose_Nuts_Enterprises said:

To update this topic, I just finished installing a 99 AW4 into my Renix Comanche. All I had to do was swap the reluctor for the OSS, and the extension housing from the old 21 spline trans. The newer trans output shaft has two snap ring grooves. The inner groove is in the exact location for the older 1 PPR reluctor. The extension housing from the 21 spline trans keeps the correct sensor location and mounting. I also swapped the entire wire harness and NSS from the old trans. Wire harness is super easy. Just take the oil pan off and unclip the three solenoid plugs, and take it out. Don't even have to mess with the valve body. Still using the renix era TCU, and everything works perfectly. As a side note, if you are going to keep the renix intake and throttlebody, swap out the TV cable while you have the pan off. That's easy to do as well.
Hope this helps, as it was difficult to find anyone that has done the swap with a follow up confirming it actually worked.


-Dan

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Cool. Thanks for the post. I think that's the easiest way for most people if you have a donor.

I didn't have a donor when I swapped the 98 AW4 into my 89 Comanche and discovered the compatibility problem. The signal converter I cobbled out of leftover parts in my electronics spare parts bin way back in 2005 is still working great.

thanks lawsoncl, you as far as I know are the pioneer for this. I seriously debated selling my late model trans and finding an earlier one, or just having my 21 spline one rebuilt. I'm not scared of the 21 spline stuff strength-wise, just the availability of t-cases and parts in general are getting hard to find. If you have a donor, like you said, it is ridiculously simple to do the swap.

Yeah, I've had an 01 in my 95 for 80k miles, and it is flawless. So many people are scared to do the conversion but it takes like 30 minutes if you have both trannys right there. I've bought an extra 01 because I find them cheaper than the correct ones. So many 00-01s are junked because the cracked head fried the motor and no one will buy the trannys because they think they can only be used in 98 to 02.