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Everything you ever wanted to know about the AW4

I'm the owner of a 1997 xj with the AW4. Recently it started slipping/shuttering in reverse "only under throttle" I have ruled out fluid levels, u-joints, and solenoids. The forward gears work normally. I understand that another 1997 AW4 is a direct swap. The next favorable option is the 1998-2001 AW4. When swapping the 1998+, the transmission tailhousing, sensor drive rotor, and output speed sensor must be carried over from the old unit. Anyone here have direct experience with this? I have found photos of the swap, but not a detailed write-up. Are these components easily interchanged?
 
If you don't want to carry over the older components, you can also grab the newer TCU and related wiring harness. I put a 99 aw4 in a 92, just wiring the gear position sensor and input speed sensor up in addition to the older TCU wiring.
 
So your saying I can grab the TCU/ harness from a 1998-2001 along with a 1998+ aw4 and swap it into a 1997? I don't mine swapping the old components off the original transmission if they can be removed without dissembling the entire transmission to do so. Looks like the rear output shaft on the transmission contains the sensor drive rotor. I would like confirmation on removal prior to purchasing a replacement transmission. I seen the pictures on the original post but it doesn't go into detail on removal.
 
Correct, though last time I tried it, IIRC the snapring grooves are in slightly different places on the output shaft. I can't remember how I solved that unfortunately.

Are you sure it's your transmission? Stuttering is more typically an engine management issue. I know it seems transmission related because it only does it in reverse, but that could just mean that you have an intermittent in a wiring harness or a wire rubbed bare and it only touches things when the drivetrain rocks the other direction on its mounts due to being in reverse.

If you swap in a 98-01 trans and TCU (instead of swapping the trans w/ the output rotor and housing swapped from the old unit onto the new one, so you keep your original TCU), the only additional wiring you need is the twisted pair cable from the ISS to the TCU's pins. It's not present on 97s since they have no ISS. Practically however this is going to involve swapping the engine bay harness and trans sub-harness since the TCU wiring is built into both of them and isn't easily separated/unplugged.
 
I'm pretty confident that it's transmission related. It started with shuttering then became more of a slipping over the last month. I'll probably film the swap and YouTube it. Do you care if I reference this post? Thanks for your input. Made my life a lot easier
 
nathanems said:
I'm pretty confident that it's transmission related. It started with shuttering then became more of a slipping over the last month. I'll probably film the swap and YouTube it. Do you care if I reference this post? Thanks for your input. Made my life a lot easier
Click to expand...

Have you tried adding some Trans-X, run it, drain it and replace the fluid (with trans-x, just a pint each time)? What does the fluid look and smell like? I lost the reverse on mine in cold weather start ups, and fixed it and bought 5 more years before it died using Trans-X. My other one lost reverse and Trans-X fixed it for 8 years now.
 
nathanems said:
I'm pretty confident that it's transmission related. It started with shuttering then became more of a slipping over the last month. I'll probably film the swap and YouTube it. Do you care if I reference this post? Thanks for your input. Made my life a lot easier
Click to expand...

Go for it, the more people who get this info the better, nothing like discovering this the hard way like I did. (I started researching this and collecting all this info in 2010 when the transmission in my 96 XJ started failing, and I bought a 98 AW4 thinking it would bolt right in. Since it was my DD and I needed to be 100% sure I'd have it running again within a day, I ended up putting the 98 trans on the shelf and buying a 93 AW4 to install instead.)
 
Hello all. So fixing to finish my 2wd/4wd converson. Next week dropping the 99 tranny to get overhauled at the tranny shop. I have a PCM question. I should not have to have my 2001 PCM reflashed once i swap in the 1999 tranny correct?? I ask because for kicks i opened up two Oreilly parts windows and looked up PCM's for both years just to verify swapability. All PCM's for both years said they would have to be programmed/reflashed upon installation. So i was then like..will the cherokee run long enough to drive to a dealership?
 
Ecomike said:
Have you tried adding some Trans-X, run it, drain it and replace the fluid (with trans-x, just a pint each time)? What does the fluid look and smell like? I lost the reverse on mine in cold weather start ups, and fixed it and bought 5 more years before it died using Trans-X. My other one lost reverse and Trans-X fixed it for 8 years now.
Click to expand...

Last year I did two separate 8 gallon fluid flushes after a water crossing mishap and replaced the solenoids. Also installed a transmission cooler so I think the fluids are good. I added some last week before a trip just to see if it made a difference. Also unplugged the TCM yesterday evening to see what would happen. No changes. I think I found a transmission sitting on a shelf for a 1997 with 92000 miles. Going to research the VIN before I purchase it.
 
Trans-X safely swells and rejuvenates old seals that may be dried out, shrunk and leaking, and keeping a valve body part(s) or accumulator pistons from moving and shifting gears. Replacing the fluid does not do that. Ir also acts like a mild solvent and will dissolve any varnish formed in the valve body areas that make the valves stick. I have used it for over 44 years and had way better luck with it than I ever had with Tranny repair shops. I never had it harm a transmission either.

As trump says "what do your have to loose" LOL.

nathanems said:
Last year I did two separate 8 gallon fluid flushes after a water crossing mishap and replaced the solenoids. Also installed a transmission cooler so I think the fluids are good. I added some last week before a trip just to see if it made a difference. Also unplugged the TCM yesterday evening to see what would happen. No changes. I think I found a transmission sitting on a shelf for a 1997 with 92000 miles. Going to research the VIN before I purchase it.
Click to expand...
 
You are a stones throw south of me. You should check out our Red River chapter threads.

01classicxj said:
Hello all. So fixing to finish my 2wd/4wd converson. Next week dropping the 99 tranny to get overhauled at the tranny shop. I have a PCM question. I should not have to have my 2001 PCM reflashed once i swap in the 1999 tranny correct?? I ask because for kicks i opened up two Oreilly parts windows and looked up PCM's for both years just to verify swapability. All PCM's for both years said they would have to be programmed/reflashed upon installation. So i was then like..will the cherokee run long enough to drive to a dealership?
Click to expand...
 
There's 20 pages and it's pretty rough to sort through that and the links throughout. I was wondering if anyone might know the answer.

If I set up a '99 AW4 in a non-XJ (my CJ7 project) and run a TCM, XJ shifter, and switches for manual shift by solenoids, but do not have a TPS, what would I expect? I assume still able to manual shift just fine, but if set to run by TCM, what will it do? Shift too early? No shift at all? I'm still working on a way to mount up a TPS to linkage on a carb.

Thanks for any help.
 
No TPS at all will throw a code. I think it will just shift early as if you were barely giving it the gas. You need the throttle-to-trans cable hooked up or it won't shift at all.
 
There's a throttle-to-trans cable? Like a kick-down?

I definitely don't have that. lol

But I can still shift by going into low and switching the solenoids, right?
 
No you also need the throttle-to-trans cable as it controls fluid pump pressure IIRC.

On the other question I would not expect anything good to happen trying to use the AW4 with a TCU and no TPS. The in 99 the TCU gets signals from the PCM, the PCM gets signals from the VSS (or whatever it is called in 99), the TPS and MAP (throttle position and Manifold Air pressure sensor rate of change of position and Manifold pressure (engine load), CPS (RPM and engine load) and the NSS to tell it what gear the shifter is in mechanical, and the PCM uses all that data to tell the TCU when and what gear for it sift to, including when to lock and unlock the torque converter!!! You do not want to be trying to shift with a locked torque converter. Sounds like you might want to go 100% manual on the shifting?

tdkask said:
There's a throttle-to-trans cable? Like a kick-down?

I definitely don't have that. lol

But I can still shift by going into low and switching the solenoids, right?
Click to expand...
 
It seems I'm stuck all-manual for the moment anyway.

But with a '99 TCU and a TPS will I be good, assuming no PCM? Does it need a VSS? Why is the pulse per revolution it looks for? I can add a VSS on my t-case I think. I really thought I had my harness sorted out. Damn.

I'll find a XJ and figure out the additional cable. Anyone have a pic by chance, though? And maybe I can make a bracket to mount a TPS via that.

While on the topic, what is the second cable on a XJ shifter?

I definitely saw a thread where a guy ran a AW-4 behind a carbed AMC V8, and a simple gabbed bracket to hold a TPS linked to carb, but it may have been an earlier AW-4.
 
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