AW4 interchangeability

Swapping in a newer AW4 (input speed equipped, I don't know exactly what year) into an '88 4.0 AW4 XJ. Far as I can tell, the output speed sensors housed in the extension housing changed. I know the spline counts will be different, the XJ will be receiving a new transfer case for this. I'm also aware the bellhousing MAY be slightly different due to the crank sensor change, I'm prepared for that as well.

I'm good with wiring, so swapping plugs/harnesses isn't an issue. According to this thread, last post, I can just swap my old output speed sensor and my old rotor onto the new trans and be good to go.

http://www.naxja.net/forum/showthread.php?t=37239

What I need to know is, can anybody confirm or deny if the output speed sensor information is true, and does anybody know of any other potential issues in this swap? Torque converters the same, solenoids operate the same, etc. It would be a real drag to get my old (still functioning) trans all tore out to find something stupid like the new output shaft will not accept my old stuff.

Any help is appreciated, I have until this weekend to find out if I can make this swap work or not. Just trying to make sure I have all the bases covered.

TIA

Believe the torque converter is the same, or will have the same 4 bolt pattern to bolt to a RENIX flexplate.

Yes, the output speed sensor is different (the fact that you have an input speed sensor indicates the donor vehicle was a 98 or later.) When I went to swap mine, I noticed that the retention clip ring was at a different spot on the shaft, so it seemed like the rotor would be able to slide up and down the shaft about a quarter to half inch. Also, the output speed sensor body is a different diameter on the old/new transmissions - I believe the older ones are thinner. The easiest way to fix this is to swap the extension housing as well. What I ended up doing is researching a bit and found that lawsoncl designed a small circuit that will convert the new 4 pulse/rev signal into a 1 pulse/rev signal that the 97-down TCU can understand.

Solenoids operate the same - BUT the connector on the harness is different RENIX vs OBD-I (iirc) vs 97 vs 98-01 (yes, 97 has its own connector, different from both older and newer vehicles. Luckily not a problem in this case) so you will end up doing a little wire splicing, no big deal really.

Another problem you are going to run into is that the output shaft changed from 21 spline to 23 spline either mid-year '90 or from 90 to 91. So you will need to swap the input gear on your transfer case, or will need to swap your transfer case as well. Your ideal transfer case donor (if you use this transmission) is a 91 to 95, since it will have the same style slip yoke / transfer case tailhousing, if you use a 96 or later transfer case you will need to swap the rear driveshaft as well (which should come from a 4.0/AW4 vehicle with the same rear axle as you have.)

Why are you swapping out a functioning transmission? I would get the parts, but keep them on the side till the transmission actually kicks the bucket.

It still drives, but it must have low line pressure, or a tired direct clutch or something. I get some strange anomalies, especially when the trans gets warm. Soft/unpredictable shifts, and for a while I kept losing TC lockup, or OD. And while I haven't had that problem as of late, I also haven't been taking the Jeep on the expressway much. It was hard to tell because everything after second gear goes mushy. Even when the TCU is unplugged.

At any rate, I got a deal on a nearly new AW4 thats just been sitting in the garage since winter. And since the Jeep is embarking on a 1000+ mile trip toward the end of August, I figured now would be a good time to put that shiny new trans to good use.

What I ended up doing is researching a bit and found that lawsoncl designed a small circuit that will convert the new 4 pulse/rev signal into a 1 pulse/rev signal that the 97-down TCU can understand.

Click to expand...

This interests me, although some people seem to claim that the output shaft on the trans has two slots for snap ring that holds the rotor, and all you have to do is use the other slot closer to the end of the trans which is originally covered up by the 4 pulse rotor. Guess I'll just have to go pull the tail housing off and see.

OK, that makes enough sense for me :thumbup:

I'll have to take another look at mine, I didn't see another slot anywhere but I didn't spend much time looking.

kastein said:

Yes, the output speed sensor is different (the fact that you have an input speed sensor indicates the donor vehicle was a 98 or later.) When I went to swap mine, I noticed that the retention clip ring was at a different spot on the shaft, so it seemed like the rotor would be able to slide up and down the shaft about a quarter to half inch. Also, the output speed sensor body is a different diameter on the old/new transmissions - I believe the older ones are thinner. The easiest way to fix this is to swap the extension housing as well. What I ended up doing is researching a bit and found that lawsoncl designed a small circuit that will convert the new 4 pulse/rev signal into a 1 pulse/rev signal that the 97-down TCU can understand.

Solenoids operate the same - BUT the connector on the harness is different RENIX vs OBD-I (iirc) vs 97 vs 98-01 (yes, 97 has its own connector, different from both older and newer vehicles. Luckily not a problem in this case) so you will end up doing a little wire splicing, no big deal really.

Click to expand...

Can I get some more info on this circuit you speak of that converts the signal so a '97-down TCU can understand?

My granddad just helped me finish an engine/tranny swap on my '97 XJ (donor engine and AW4 tranny are from a '99 XJ), and of course the new tranny has 7 wires as opposed to 5 on the old one. Needless to say, its driveable, but the tranny is not shifting properly. Will start off in 1st gear but immediately shifts up into overdrive.

Any information you can provide that will point me towards a solution for my problem is greatly appreciated!

I for some reason cannot find the thread it was posted in. Your best bet is to pm lawsoncl, he originally designed the circuit. Assuming I find some free time next week I will finish the pcb artwork I was working on for it and post it here so everyone can have boards made and solder the parts to them instead of having to breadboard the whole thing.

his dang inbox is full!

Raspberry said:

his dang inbox is full!

Click to expand...

Dang my ears were burning. Actually sent me an email that you were trying to pm me but my box was full. Got that remedied.

Anyway, have a look at these links. I had a few other pictures around here but I can't find them again. It was cobbled together from pieces in my spare parts bin. You'll need to breadboarding skills to put it together and test it out. For something just thrown together its actually worked pretty well. Sounds like kastein is going to clean it up a bit and do a real board.

http://mysite.verizon.net/~chris83803/AW4_Sensor_Converter.pdf
http://mysite.verizon.net/~chris83803/board.jpg
http://mysite.verizon.net/~chris83803/box_mounted.jpg

The basic function of this circuit is to take in the 4 ac pulses/rev, clean up the signal and divide it by 4 so you get a 1-pulse/rev output. The Renix setup was expecting a switch closure once per rev whereas the newer setup had a magnetic pickup that gave an a/c pulse 4 times per rev.

The variable resistor was used because I didn't know how sensitive it would need to be as the voltage of the input varies with the rpm (I measured from zero up to 30 volts peaks). Too sensitive and it would pickup random noise. Not sensitive enough it wouldn't sense motion until the rpm was much higher. Just substitute something close to 14k. The filtering, a/c coupling, and clipping on the input side is probably a bit overkill, but I had the parts handy and I really wanted it bulletproof.

Looks all greek to me, to be honest! I might just be better off taking the tailcone with sensor/rotor off the old tranny and installing it onto the newer one.
Its probably more work doing it this way, but at least I can make sense of it

I do appreciate the reply!!

I'll still be interested in what kastein comes up with though and will be keeping watch

lawsoncl said:

Sounds like kastein is going to clean it up a bit and do a real board.

<snip>

The variable resistor was used because I didn't know how sensitive it would need to be as the voltage of the input varies with the rpm (I measured from zero up to 30 volts peaks). Too sensitive and it would pickup random noise. Not sensitive enough it wouldn't sense motion until the rpm was much higher. Just substitute something close to 14k. The filtering, a/c coupling, and clipping on the input side is probably a bit overkill, but I had the parts handy and I really wanted it bulletproof.

Click to expand...

I was already partway through designing the board back in like... february or march or so, but never finished it because I never got around to putting the tranny in that needed it :dunce:

I spent some time reverse engineering the stock TCU for another project I'm working on. I recall the ISS and OSS signal lines (it was a '98 model year TCU) leading through some signal conditioning circuitry and I seem to remember it involving a quad op-amp or comparator, some capacitors, and a few ~1/4 watt (larger than normal) SMT resistors. When I find my box of XJ electronics projects (it has been AWOL since I moved, along with the box of spare U-joints, control arm bushings, and motor mounts... wish I could find that!) I will figure out how the stock TCU conditions the signals before feeding them into the MCU and we can just duplicate that if it's simpler than your design.