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Everything you ever wanted to know about the AW4

I just went thru my email and it was in the spam box. Glad you told me. I am now in the head scratching deer in the head light look phase. But im off to work so I will decipher it more tomorrow. Thank you
 
Just an update I pulled the fuse and I can drive it if I shift it. So not sure what that means. I know it makes it like a manual but at least the tranny works. Does that mean the tailshaft sensor is bad? I know lawsoncl said that it should be shifting with the wrong sensor but just early but it isn't. Is it bad to drive it with the tranny being shifted manually?
 
It's perfectly fine, you won't hurt anything, just won't have lockup.

I suspect your problem is the sensor, but not sure. I suspect it could also be the NSS or TPS - what are the exact symptoms? No shifting at all? What gear does it seem to be in?

As luck would have it I just found the 87-97 tailhousing, sensor, 91-96 harness (not exactly sure on year) sitting in my stash of parts and I'm pretty sure I know where the 1pulse/rev magnet rotor is in my storage unit, if you end up needing it I can ship it to you for basically cost of shipping, it's not doing me any good. I'd really suggest building the electronics signal conversion box since it's easier (at least in my mind) and doesn't involve dropping the transfer case, just soldering stuff together.
 
It acts like its stuck in first gear. Never shifts no matter what rpm. I have the old tranny with all the stuff except the wiring and pulse rev magnet. I cut the wiring to splice in the 98 part. I have looked at the copy I was sent and it wouldn't be to hard but I'm not much of a solderer.
 
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I'll see if I can find the magnet tomorrow.

I'd have to suspect the sensor+magnet being wrong, but I'm honestly not sure. Your TCU could have also let out the magic smoke, there's a chance the RENIX ones that lawsoncl has tried this with (I think?) are more resilient and handled the voltage pulses from the later style sensor + rotor more gracefully than the 94 TCU did, I haven't reverse engineered the earlier TCUs enough to know for sure what they can handle for speed sensor signal input abuse.

It acting like it's stuck in first does tell me that it's getting power, though - if it was stuck in OD I would suspect a blown fuse or otherwise lacking power to the TCU since OD is both solenoids off.
 
Where is the tcu located? The old tranny drove and shifted fine just no reverse. I did nothing but swap transmissions. The 98 has the sensor it came with I just cut and spliced the old wiring harness into the new one. There is another sensor on the front of the franny towards the bellhousing that wasn't on hte 94 and currently has nothing plugged into it. But for now I'll just shift it manually if that isn't hurting anything.
 
It's up under the passenger side of the dash, pretty easy to get to.

Most of what I'm worried about is that the new sensor you have in there actually produces a voltage, while the old one was just a switch - if the voltage it produces ends up being over what the TCU input can withstand it could burn it out.

The extra sensor at the front of the trans is no big deal, just leave it there so the fluid doesn't leak out.
 
This is a great thread for the AW4. I'm having problems with mine in an '87 Renix. Sometimes, all shifts are fine. Then, you pull out of the driveway and it will revup but not shift out of first. Seems to do this more when the vehicle is warmed up. If you pull the fuse on the TCU, it will shift like a manual so I think the trans is ok. Checked resistance on the solenoids and they seem ok. Put a new TPS in and refreshed all the grounds. Still same problem. How do you check the speed sensor? They run almost $100 new. Don't really want to just buy one unless mine is proven bad. Any ideas?
 
For an 87-97, put a 12v test light on the pin at the TCU for the speed sensor, then with the transfer case in neutral, put the transmission in 1-2 and let the engine idle. You should see the test light flicker a bit - if not, put the transmission in neutral as well, the output shaft will spin slowly and you should see the test light blink regularly. Shut the engine off before putting it back in park.

For 98-01 it's a bit more difficult to test, but that's not exactly relevant right now.


BigBluetrg, I did find the magnet rotor (and the speed sensor) off my old 96's trans if you end up needing it. I'm not sure what else to test next, I don't really do well at debugging electrical issues over the 'net. Let me know if you need it, should fit in a small flat-rate no problem and it's not doing me any good sitting here.
 
I've got a 97 Cherokee which is the odd year for the TCU as it only has 26 pins instead of 32. I'm looking for the wiring harness pin-outs for it and have had no luck. Can find it for the 32 pin connector but not for the 26 pin connector. Anyone have the information for this or a pointer to it?

I'd even be happy with just wire color/function.

Thanks
This is a great thread, learned a lot...

97 Cherokee
5 inch lift
 
Selecting and HOLDING Second Gear

This is a great thread! Alright so I want to run this by the trans gurus:

Selecting and HOLDING Second Gear

According to the top of this thread and Rad Design's page here: http://radesignsproducts.com/Tech.html

Putting the shifter in 1-2 and applying +12v to Solenoid #2 will put me into Second Gear and KEEP me there - correct?

The shifter supplies +12v to Solenoid #1, and the TCM chooses when to apply power to Solenoid #2 for a 1-2 up or down shift.

It is very hard to use the 1-2 position of the shifter for me on the steep roads here: If I drop below 26mph in the 1-2 shifter position, it drops into 1st gear which has about made me swap ends once - it's bad on a tight corner anyway, and we have lots of those.
 
Overriding and supplying power to solenoid 2 will keep you in 2nd, yes. Bear in mind that I'm not sure what effect, if any, there could be on the TCU once it starts seeing the opposite bias voltage on the pin it uses to send + voltage to the transmission shift solenoid. A simple diode may be all that is necessary to ensure no damage to the TCU takes place.
 
I don't believe you'll have an issue just pulling it to 12V but I'd suggest not doing it anyways just to be on the safe side. It's as simple as using an SPDT switch instead of an SPST - cut the wire for solenoid 2, wire the solenoid to the COM terminal, the TCU to one of the others (choose it so that the switch position is where you want it) and the other terminal to ignition switched 12V. If you also want a first gear override to hold first, use an on-off-on SPDT, one of the ON positions will be factory behavior, the other will be forced second gear, the off position will be forced first gear.
 
child9 said:
Overriding and supplying power to solenoid 2 will keep you in 2nd, yes. Bear in mind that I'm not sure what effect, if any, there could be on the TCU once it starts seeing the opposite bias voltage on the pin it uses to send + voltage to the transmission shift solenoid. A simple diode may be all that is necessary to ensure no damage to the TCU takes place.
Click to expand...

OK, I do have some blocking diodes on hand.

kastein said:
I don't believe you'll have an issue just pulling it to 12V but I'd suggest not doing it anyways just to be on the safe side. It's as simple as using an SPDT switch instead of an SPST - cut the wire for solenoid 2, wire the solenoid to the COM terminal, the TCU to one of the others (choose it so that the switch position is where you want it) and the other terminal to ignition switched 12V. If you also want a first gear override to hold first, use an on-off-on SPDT, one of the ON positions will be factory behavior, the other will be forced second gear, the off position will be forced first gear.
Click to expand...

Hmm, that is probably better, as it would isolate the TCM entirely from my bastardization ;) I'll see if I can find a SPDT that fits my little panel.

Thank you both!
 
kastein said:
For an 87-97, put a 12v test light on the pin at the TCU for the speed sensor, then with the transfer case in neutral, put the transmission in 1-2 and let the engine idle. You should see the test light flicker a bit - if not, put the transmission in neutral as well, the output shaft will spin slowly and you should see the test light blink regularly. Shut the engine off before putting it back in park.

Thanks for the reply-I didn't see it until today. I hooked up a meter to C3 on the TCU and watched when I drove. I could see the off/on at low speeds and then of course it got to fast for the meter. Once it warmed up, the voltage became constant and it wouldn't shift out of first again. I went underneath and moved the wires around and it seemed fine for a couple of days. Now I get no voltage change at all and of course it's in first. I put a switch on the TCU and if I turn the power off, I can drive it by shifting manually. Do the speed sensors go? I don't mind swapping a new one in but I'm wondering if it could still be an electrical short somewhere. It's really dirty in there. Do you have a close up picture of where the speed sensor is? I saw on one of your earlier posts a picture of a 95 I think. I'm trying to figure out what harness does what.

Thanks for the great info!!
Click to expand...
 
Sure sounds like the speed sensor to me. I will see if I can get a pic sometime but no guarantees. Its the part behind the 4x4 shifter linkage bracket at the very back of the trans where the tcase bolts on, drive side.
 
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