88 to 97 AW4 swap??'s

okay so I've asked a few of you on here already... but I'm still having problems!

here's the story:
-got an 88 xj
-everything is in good shape...except tranny is toast
-so I replace burnt up tranny with a tranny and t-case from a 97 xj
-I used the 88 wiring to hook up everything to the new tranny
-while test driving with the 97 tranny, it shifts to 3rd gear before 30mph and then will not down shift after slowing down to a complete stop
-I thought the speed sensor in the rear housings where different..turns out they are the same
-i have switched the tps several times with spares i have lying around...and nothing.
-I have checked all the wiring and nothing is pinched or broken


i'm thinking maybe the tcu is shot?
someone is telling me the newer ones have more solenoids than the older ones, however I only see three.

PLEASE HELP

did you drive it doorless or something in the rain, or do you have a leak somewheres, i had a tranny computer get wet and it did the exact same thing, if you go to a bone yard you could get one pretty cheap

hopefully you didn't get rid of the old tranny yet.

the problem lies in the output transmission speed sensor. (different from the vehicle speed sensor). pre '96 models use a spinning magnet with reed switch, while the later years use a proximity sensor. the older setup gets 2 pulses per revolution, while the newer gets 4.

the solution: remove the transfer case from the transmission. remove the 4 pronged... sleeve (for lack of a better word) from the output shaft of the transmission. replace it with the one from the old transmission. (they are held on with snap rings held into grooves).

after you do that, everything should work perfectly.

i don't understand what you are refering to?
I already took the transfer case and transmission 4wd extention housing off and replaced the rotor on the trans output shaft and don't recall a four prong anything in there??
however the rotors were identical but i switched them anyway

I know the newer like 98 model years + have the speed sensor up front on the driver side by the bell housing...this 97 doesnt have that front sensor.

and yes I still have the old transmission

please explain

h2opete987 said:

hopefully you didn't get rid of the old tranny yet.

the problem lies in the output transmission speed sensor. (different from the vehicle speed sensor). pre '96 models use a spinning magnet with reed switch, while the later years use a proximity sensor. the older setup gets 2 pulses per revolution, while the newer gets 4.

the solution: remove the transfer case from the transmission. remove the 4 pronged... sleeve (for lack of a better word) from the output shaft of the transmission. replace it with the one from the old transmission. (they are held on with snap rings held into grooves).

after you do that, everything should work perfectly.

Click to expand...

yeah i guess i'm off to pull-a-part to find a tcu to swap in

xalexjx said:

did you drive it doorless or something in the rain, or do you have a leak somewheres, i had a tranny computer get wet and it did the exact same thing, if you go to a bone yard you could get one pretty cheap

Click to expand...

i know the tv cable is there... but I have also heard that the aw4 downshifts from controlled line pressure and somewhere in the valve body this could be ajusted.
would this be a possibily? I'm thinking no adjustment would be needed as I drove the 97 xj which was the donor for the 88 and it drove and shifted just fine.

sixditch said:

i know the tv cable is there... but I have also heard that the aw4 downshifts from controlled line pressure and somewhere in the valve body this could be ajusted.
would this be a possibily? I'm thinking no adjustment would be needed as I drove the 97 xj which was the donor for the 88 and it drove and shifted just fine.

Click to expand...

Oh boy...you're saying you didn't swap the TV cable to your 88's? There's part of your problem if you didn't, theres about 5" of differences in them.

90PioSport99 said:

Oh boy...you're saying you didn't swap the TV cable to your 88's? There's part of your problem if you didn't, theres about 5" of differences in them.

Click to expand...

no i didnt...oops
i didn't even measure or even think about that

i hope that is the problem...thanks for the info.

sixditch said:

no i didnt...oops
i didn't even measure or even think about that

i hope that is the problem...thanks for the info.

Click to expand...

Yeah assuming you've still got the Renix intake/throttle body you need to use the 88's cable. It's easy to replace, drop the pan, take off a 10mm bolt that holds it in on top of the tranny, and pop it out of it's reel inside the trans. Let me know how it works for you. Other than this did you really not have to change anything else out? I was under the impression that it was huge PITA to change from a 96- to 97+ AW4.

90PioSport99 said:

Yeah assuming you've still got the Renix intake/throttle body you need to use the 88's cable. It's easy to replace, drop the pan, take off a 10mm bolt that holds it in on top of the tranny, and pop it out of it's reel inside the trans. Let me know how it works for you. Other than this did you really not have to change anything else out? I was under the impression that it was huge PITA to change from a 96- to 97+ AW4.

Click to expand...

well i will swap out the tv cables this weekend and hopefully I will be good to go...we'll see

so far I've kept the 88 wiring by hooking it up to the 97 solenoids and will be swapping tv cables and of course the 23 spline tcase to match the 97 tranny.
yep that's it so far...

sixditch said:

well i will swap out the tv cables this weekend and hopefully I will be good to go...we'll see

so far I've kept the 88 wiring by hooking it up to the 97 solenoids and will be swapping tv cables and of course the 23 spline tcase to match the 97 tranny.
yep that's it so far...

Click to expand...

Hey sixditch, what'd you find out after swapping TV cables? Is all well?

actually, i swapped the TCU and everything seems to be fine.
I did look at the tv cables and yes they are different lengths by about 5"... but the pull is the same so I couldn't justify the swap.
Am I missing something??

i haven't driven it much, but everythings seems to be in good working order!

Thanks for all the help!

sixditch said:

actually, i swapped the TCU and everything seems to be fine.
I did look at the tv cables and yes they are different lengths by about 5"... but the pull is the same so I couldn't justify the swap.
Am I missing something??

i haven't driven it much, but everythings seems to be in good working order!

Thanks for all the help!

Click to expand...

Did you change to the TCU from a 97+ unit? And what exactly did you change/modify to do the swap? My buddy has an 87 XJ that the AW4 may go out in before too long and since there are so many 97+ around here it might be worthwhile to use a newer one, I just never thought it was even close to feasible. It sounds like for you it was pretty much just bolt n go though eh?

h2opete987 said:

the problem lies in the output transmission speed sensor. (different from the vehicle speed sensor). pre '96 models use a spinning magnet with reed switch, while the later years use a proximity sensor. the older setup gets 2 pulses per revolution, while the newer gets 4.

Click to expand...

I believe the changeover happened in 98 instead of with the OBD changeover. The rear speed sensor went from 1 pulse/rev to 4-pulses/rev and a front sensor was added. The Renix rear sensor is physically too long to install if the tranny has teh later 4-lobed rotor. The Renix era rear sensor was a reed relay, and I'm reasonably sure the 90-97 were as well since I recall seeing the sensor part numbers were the same. I know 98+ has a hall effect sensor that generates a voltage spike as the magnets pass by. The hall effect sensor used in 98+ happily triggered the Renix TCU in my MJ. Problem was that it was triggering 4x as fast so it was shifting at 1000 rpm. I solved by making an adapter box to divide the 4-pulses per rev down to 1 pulse per rev (no donor tranny to swap the sensor/rotor).

90PioSport99 said:

Yeah assuming you've still got the Renix intake/throttle body you need to use the 88's cable.

Click to expand...

I don't think that's true. I happen to have a 99 AW4 installed in my 89 MJ using the 99 TV cable.

lawsoncl said:

I don't think that's true. I happen to have a 99 AW4 installed in my 89 MJ using the 99 TV cable.

Click to expand...

Apparently it's not true since he's driving around that way too. To me it just always made sense to swap them :dunno:.