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Transmission swap

okBrian

NAXJA Forum User
I have a 90 4x4 xj with 4.0, AW4, 231tc. I just bought it a couple of months ago and the odometer reads 134k. The AW4 shifts poorly between 1st & 2nd (like it's slipping) 2nd to 3rd and 3rd to OD is fine. I found an AW4 out of a 1998 xj with 88k miles on it. I'd like to swap out the transmissions. I think there might be an issue with spline count? How tough a swap will this be? Thanks for the help!
 
You do have different spline counts. You'll want a 91+ transfer case to match spline count of the 98 aw4. It can be done, but it's not exactly a bolt-in affair.


From http://www.jeepforum.com/forum/f11/sourcing-4wd-conversion-parts-junkyard-1145695/#post10686432 :

With the switch to two sensors in 1998, the rear speed sensor changed from 1 pulse/rev to 4 pulses/rev. So, you need to swap the rear sensor rotor and sensor if putting a 98+ AW4 into an older Cherokee that expects 1 pulse/rev.

1997-2001 AW-4’s have a different Neutral Safety Switch (NSS) than the 1996 and earlier.

The transmission input spline count is 21 splines for 1987-1990 and 23 splines for 1991-2001.

87-90

0.70:1 OD ratio
21 spline output shaft
Electrical connections- early model
One transmission speed sensor (output only)

91-96

0.75:1 OD ratio
23 spline output shaft
Electrical connections - early model 6 pin wire connector
One transmission speed sensor (output only) 6 pin wire connector

97-

0.75:1 OD ratio
23 spline output shaft
Electrical connections - late model 8 pin wire connector
One transmission speed sensor (output only)

98-01

0.75:1 OD ratio
23 spline output shaft
Electrical connections late model 8 pin wire connector
Two transmission speed sensors (input and output)
 
The AW4 shifts poorly between 1st & 2nd (like it's slipping) 2nd to 3rd and 3rd to OD is fine.


Is the fluid and filter fresh ? Is it the correct fluid ?

Have you tested the Throttle Position Sensor ? Have you adjusted the Transmission Pressure Cable ? Have you tested the solenoids and speed sensors ?

Why would you put in another transmission without diagnosing the issue with the original one ?
 
I agree with Tim. It may not be the transmission, it may easily be a bad TPS, throttle cable out of adjustment, old fluid, or an electrical problem between the TCU (tranny computer), like a bad ground or loose wire and the electric solenoid in the AW4. Solenoids are easy to replace.
 
Thanks guys! TimMN & ecoMike I should have provided more information. Here's what I have done so far to diagnose the problem.
1st drained and replaced filter with all new dex4 fluid. No improvement
2nd replaced and adjusted TPS checked all voltages OK. No improvement
3rd adjusted kickdown cable per proceedure found on here. No improvement
4th disconnected connector to TCU to look for bad connection or anything obviously bad. No improvement
5th replaced solenoids new fluid. No improvement

So that is where i'm at on this troubleshooting
 
Output speed sensor is mounted on the driver side of the rear end of the transmission, right underneath the metal plate that supports one end of the transfer case shift linkage / bellcrank. In your year it is a reed switch that closes once per output shaft revolution. If you jack the vehicle up and put the rear axle on jackstands (chock the front wheels and put it in 2wd) and put it in gear, then use a test light at one of the pins on the wiring harness connector (near the tranny dipstick tube) in the proper sockets it should blink once per revolution.
 
Would this sensor being bad cause the symptoms I am having with the shifting from 1st to 2nd being erratic (slipping) most of the time I have to let off the gas a little to get it to shift.
 
Ask Lawsoncl, he should know. I think yes, but am not sure. Also could be wiring to the TCU.
 
why not just rebuild the trans u have and not have to f with all the info headache. ive seen rebuilt one go for around 5-6 hun.
 
Why rebuild at all? AW4s can be had for under 150 in good used condition all day long and last forever.

Keep the old one for the day when there aren't more XJs than you can shake a stick at in your local pull a part, waiting to get crushed.
 
Thanks to all that responded! I picked up this 98 AW4 for next to nothing on a knee jerk reaction type move not knowing how difficult a swap it might be. I'll continue to troubleshoot this one and if I do swap I'll find a like aw4 90 to swap with. I will sell the 98 aw4.
 
Next to nothing? I'd keep it. It's way newer and probably in better shape than any 90 AW4 you can find right now. It's not bolt in, but it's newer and you already went to the trouble of getting it...

The only downsides - you will have to unbolt and swap the 4wd adapter housing on yours, swap the output speed sensor rotor and sensor as well. You'll have to get a different transfer case (a 91-95 would be a ideal swap for you.) You'll need to do some minor wiring splicing but it's all easy stuff.
 
Ask Lawsoncl, he should know. I think yes, but am not sure. Also could be wiring to the TCU.

Usually if the speed sensor or its wiring is bad, it'll just stay in 1st gear. The speed sensor in the 98 AW4 is 4-pulses/rev versus the 1-pulse per rev in yours. You can search and find the writeup on swapping the rotor and sensor over from your old AW4. The difference in the 4th gear ratio won't the shifting noticeably.
 
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