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TC lockup hack

H

halmca

NAXJA Forum User
Location
Tallahassee, FL
Due to having hit a snag in converting my '98 from 2x to 4x4 (well-documented in two other threads) I find myself manually shifting my '97 AW4*. I have R, P, 1st, 3rd, and 4th. Notably missing is the lock up TC (as well as second gear)

Since the wire harness for the transmission is unplugged anyway, I see that the TCM applies power to the TC lockup solenoid, via a dark blue/white stripe wire. (circuit C-22)

I'm fixin to rig an interruptible 12v to that wire in hopes of energizing the lock up solenoid when I wanna hit the super slab. Think it'll work?

* After extensive and belated research I have discovered that some '98's were delivered with '97 transmissions. The supposedly '98 AW4 that I bought came from an XJ bearing a '98 VIN.
 
It'll work; that's basically what you do when you replace the control module with a "manual" electric shifter, such as the RADesigns Rail II.

IF you decide to forgo the electronics and stay manual, you'll probably want to look at getting something like the Rail II. Technically speaking, you can do it all with just 3 toggle switches, one for the TC and then one for each of the 2 shift solenoids. The fun is managing the "binary" pattern to shift it

1st Gear: Solenoid 1 on, Solenoid 2 off
2nd Gear: Solenoid 1 on, Solenoid 2 on
3rd Gear: Solenoid 1 off, Solenoid 2 on
4th Gear: Solenoid 1 off, Solenoid 2 off

It may be helpful to wire up a pair of switches and verify that the solenoids are working; it'll make troubleshooting the electronics much easier. If I'm not mistaken, you won't ever get 2nd gear and you only get 4th because there's a manual safety valve in place to kick it into 4th; you get 4th but only after revving it to near redline. All said, you're going to either have to figure out the wiring issue or your going to need to replace it with a "manual" electric option; running an AW4 pure-manual isn't a viable long term option realistically speaking. I'm sure it can be done, but yeah...
 
Jim Malcolm said:
It'll work; that's basically what you do when you replace the control module with a "manual" electric shifter, such as the RADesigns Rail II.

IF you decide to forgo the electronics and stay manual, you'll probably want to look at getting something like the Rail II. Technically speaking, you can do it all with just 3 toggle switches, one for the TC and then one for each of the 2 shift solenoids. The fun is managing the "binary" pattern to shift it

1st Gear: Solenoid 1 on, Solenoid 2 off
2nd Gear: Solenoid 1 on, Solenoid 2 on
3rd Gear: Solenoid 1 off, Solenoid 2 on
4th Gear: Solenoid 1 off, Solenoid 2 off

It may be helpful to wire up a pair of switches and verify that the solenoids are working; it'll make troubleshooting the electronics much easier. If I'm not mistaken, you won't ever get 2nd gear and you only get 4th because there's a manual safety valve in place to kick it into 4th; you get 4th but only after revving it to near redline. All said, you're going to either have to figure out the wiring issue or your going to need to replace it with a "manual" electric option; running an AW4 pure-manual isn't a viable long term option realistically speaking. I'm sure it can be done, but yeah...
Click to expand...

Thanks for your thoughtful and encouraging post. Long term, I will be replacing my nicely rebuilt AW4 of the earlier design (no input shaft speed sensor) with another nicely rebuilt AW4 of the later design. (with input shaft speed sensor)

BTW, I get R, P, N, 1, 3 and 4th with no revving -- and with the connector between the TCM and solenoids unpluged. In the short run, while I'm looking for a 'late model AW4, I would like to occasionally lock up the torque converter. It has been a nice stroll down memorlane, however, as it's been decades since I have driven a car of any sort w/o lockup TC. I am spoiled. I remember now why we called 'em 'slushboxes'.


Thanks again!
 
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You could if you got lucky and your '98 XJ had a '97 transmission. However, if it didn't, I think you'd find that the TCM connector is quite different between the two. By "TCM connector" I'm referring to the plug that plugs directly into the TCM under the instrument panel. Along with the changes in the transmission (among which is an input shaft speed sensor) is a physical change in the TCM that to my eye, prevents plugging the car into the 'wrong' TCM. (In addition to the electrical changes inside.)
I have good pictures of both connectors but can't post 'em cuz I don't know how -- unless I join photobucket or some other image hosting service.

EDIT: the hack did work and I now have the TC lockup. The wiring diagram in the FSM has the wrong color. The correct color for the lock up solenoid is white with a brown tracer.
 
Last edited:
halmca said:
EDIT: the hack did work and I now have the TC lockup. The wiring diagram in the FSM has the wrong color. The correct color for the lock up solenoid is white with a brown tracer.
Click to expand...


Skimming the wiring schematic in the FSMs, I think that's a 94 or 95 transmission that shows white/black-stripe for the torque converter solenoid wire.
 
lawsoncl said:
Skimming the wiring schematic in the FSMs, I think that's a 94 or 95 transmission that shows white/black-stripe for the torque converter solenoid wire.
Click to expand...
Indeed. Irrespective of what 'year' this transmission is, it is wrong for my XJ. That's the bad news. The good news -- such as it is -- is my XJ is almost fully functional with manual shifting and my manually plugging in my TC lockup to my cigar lighter. (the most handy source of 12VDC.)

I'm on the hunt for a 1999-2001 AW4, as I believe that's the best solution to my manifest woes. So if you have one with which you'd care to part, and you live in God's country (the SE USA) do bring the matter to my attention with price and VIN of the donor Jeep. Um if it's not too much to ask . . . I might consider a 1998, if you're willing to sign an affidavit in blood regarding whether it has an input shaft speed sensor, and a four pole reluctor.
 
Jim Malcolm said:
car-part.com is showing one out of a 2000 for $400 up in Gainbridge, GA
Click to expand...
Bainbridge., GA. It's now in my garage. Its XJ caught fire under the hood. 100k on the clock, and it was in daily use before the fire. Trying to decide whether to have it rebuilt, or simply install it as is and go to church for a few months. Thanks for the tip.
 
halmca said:
Bainbridge., GA. It's now in my garage. Its XJ caught fire under the hood. 100k on the clock, and it was in daily use before the fire. Trying to decide whether to have it rebuilt, or simply install it as is and go to church for a few months. Thanks for the tip.
Click to expand...

I would install it as-is unless you have an urge reason to throw a chunk of money at someone who may or may not know what they're doing.

I would measure the solenoid resistance at the harness to make sure they measure okay. Otherwise, there is no need to remove the pan. The "filter" is just a metal screen and doesn't need routine replacement. Look and see if you have any oil leaking out the front shaft, and if the rear seal looks okay. Now would be a good time to remove and clean the NSS while you have good access.

You probably know this already, but just in case, make sure the t/c is fully seated in the trans before bolting up the bellhousing, and that you can still move the t/c back-n-forth a little bit after. If the t/c isn't fully seated, you'll damage the front pump.
 
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