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Difference between early and late model AW4's

dave92cherokee

NAXJA Forum User
Location
Lynchburg, TN
I might be picking up a 99 xj that is said to have a bad tranny. I've looked on here but can't find anything mentioning it but just wanted to be sure before actually buying it. I've got a 93 xj country and wanted to know if it's a direct swap between the two. I know the TCM's are different but the only thing on the 99 that's bad is the tranny itself. I know there's also a difference between the output of the two between 2wd and 4wd but if that's the case I can swap the output from one to the other if need be.
 
I have heard there was a sensor change in 98 where a second sensor was added to the transmission. Others will probably chime in with the exact name but I've heard that older AW4's will not work with a post 98 chassis.
 
Changing output shaft is basically tearing the whole trans down, which in that case, you might as well rebuild the bad trans.. given that the case is still in good shape. But I do believe aside from the added sensor that it is pretty much bolt in
 
Its very rare to find a 99 with a bad tranny. There is a good chance the tranny itself is fine, and that something else is messed up .... TPS, TCM, low fluid, etc.

What exactly is the tranny doing that the guys thinks its shot?
 
Not sure what it's doing as he hasn't responded back yet. I wasn't talking about changing the output shaft more the tailcone to swap between 2wd and 4wd. I know the CPS mounts in the same place for both years whether the CPS itself changed. The only sensor that might have changed would be the speedo to interact with the 97+ CCD bus and OBD2. The NSS should be the same throughout and if not could be swapped over with ease, as far as the electrics go that go from the main harness to the trans itself is where I'm up in the air. I know physically it'll fit but wasn't sure about the connections if they're different or not.
 
I wasn't talking about changing the output shaft more the tailcone to swap between 2wd and 4wd.

Swapping to 4wd requires transmission mainshaft replacement not just a tail cone to adpater swap on the AW4.

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
One transmission speed sensor (output only)

97-mid 98

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

mid 98-01

0.75:1 OD ratio
23 spline output shaft
Electrical connections late model
Two transmission speed sensors (input and output)
 
Last edited:
I don't think '96+ is interchangable with pre '96. I remember thinking the wiring was different because of the OBD switch and the TCM was intergrated with the ECU.
ECU and TCU are separate through the whole life of the XJ family - you're probably thinking of the grand cherokee with the integrated TCU/ECU.

Not sure what it's doing as he hasn't responded back yet. I wasn't talking about changing the output shaft more the tailcone to swap between 2wd and 4wd. I know the CPS mounts in the same place for both years whether the CPS itself changed. The only sensor that might have changed would be the speedo to interact with the 97+ CCD bus and OBD2. The NSS should be the same throughout and if not could be swapped over with ease, as far as the electrics go that go from the main harness to the trans itself is where I'm up in the air. I know physically it'll fit but wasn't sure about the connections if they're different or not.
There is also the input/output sensor change as MJR said - and on the 93, the mounting boss for the input sensor won't even be machined out for you. Also the speedo sensor shouldn't be an issue, the electric VSS started in 91 and is mounted to the transfer case rear output housing (or in 2wd XJs, the output tailcone I guess) and in any case I am pretty sure I read somewhere that it's the same mounting as the mechanical speedo takeoff, just unbolt one and bolt the other in.

Swapping to 4wd requires transmission mainshaft replacement not just a tail cone to adpater swap on the AW4.

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
One transmission speed sensor (output only)

97-mid 98

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

mid 98-01

0.75:1 OD ratio
23 spline output shaft
Electrical connections late model
Two transmission speed sensors (input and output)
Thanks for the level of detail here - that clears up the confusion about the 98 one/two sensor switchover... I'll have to remember this in the future.

EDIT: What I'd do - if it sounds like it's an electrical/fluid issue, buy it and fix. If it sounds like a clutch pack issue, buy it and fix :looney: - you can get the rebuild kit for like $150something on ebay.
 
A minor correction.

97

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

98-01

0.75:1 OD ratio
23 spline output shaft
Electrical connections late model
Two transmission speed sensors (input and output)
 
Yah I'm still waiting on him to write back with what was wrong with it as I can pick it up with 183k miles for under a grand and engine, interior, and body are immaculate.
 
One other comment. With the switch to two sensors, the rear speed sensor changed from 1 pulse/rev to 4 pulses/rev. Hence the need to swap the rear sensor rotor and sensor if putting a 98+ AW4 into an older setup that expects 1 pulse/rev.
 
One other comment. With the switch to two sensors, the rear speed sensor changed from 1 pulse/rev to 4 pulses/rev. Hence the need to swap the rear sensor rotor and sensor if putting a 98+ AW4 into an older setup that expects 1 pulse/rev.

Any pics of said change over? difficulty? Thinking of going from a 89' to 98 newer trans. ant electrical connnections that won't work?
 
Any pics of said change over? difficulty? Thinking of going from a 89' to 98 newer trans. ant electrical connnections that won't work?

Putting a 98 into a 89 both connectors will be different but you can cut and splice. You just won't use the input sensor wires.

Via Easter Jeep Safari. :)
 
Putting a 98 into a 89 both connectors will be different but you can cut and splice. You just won't use the input sensor wires.

Via Easter Jeep Safari. :)

neither of the input sensor wires? sounds like the pulse per min or what ever then don't matter... doesn't speedo on my 89 pick up from the transfer case anyway?
 
neither of the input sensor wires? sounds like the pulse per min or what ever then don't matter... doesn't speedo on my 89 pick up from the transfer case anyway?

No still have to deal with the output sensor issue. Those are for the trans controller. It doesn't use the the vehicle speed sensor.
 
No pictures that I have - but you can distinguish them pretty easily. A 98 or newer will have a sensor with (I think) two wires going to it up at the front near the bellhousing / shift cable bracket, while a 97 or older will have a mounting boss for one but it won't be machined out and there will be no sensor present.
 
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