AW4 lockup and shifting troubles.

89 4.0 AW4 249k miles. Its kinda hard to explain this and it make sense.

I rebuilt the engine recently. Before the rebuild the tranny worked fine, now it doesnt. When i first take off the tranny will go into first then shift up through the gears as it should. When i start to just go a constant speed, say 45mph, the tranny wont shift into OD and lock the torqe converter like it should. Sometimes it will not even go past second gear, then when its as if it shifts into neutral and the engine just revs up. Then as you start to come to a stop then tranny will not go into first, even if you have the gear selector in the 1-2 setting. You have to turn the jeep of and restart it for it to go into first.

I have checked the inline fuse to the TCU and I tried to check the Speed sensor in the tranny (the white 1 wire connector) but i wasnt getting pulsating AC voltage, but i may have been doing it wrong.

Help please

I've found that most AW4 shifting problems get traced back to a bad TPS. The second and third leading causes seem to be a TV cable (often wrongly called a kickdown cable) out of adjustment, or low fluid.

Unplug the harness from the TCU and shift manually through the gears (no 2nd) and see if everything is working fine, that will help you determine if it's an electrical or mechanical problem.

I was thinking it could be electrical because i have to restart my jeep to get 1st gear. Ill go try the unhooked TCU and report back.

I pulled the fuse and it all works now like you said. I tried to test the VSS but i think i did it wrong cause the voltage did not pulse

the AW4 has it's own speed sensor built into the trans case.

check the grounds on the pass side of the block, and make sure you have a good engine-to-body and battery-to-body ground

Muddy89XJ said:

I have checked the inline fuse to the TCU and I tried to check the Speed sensor in the tranny (the white 1 wire connector) but i wasnt getting pulsating AC voltage, but i may have been doing it wrong.

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You're talking about the wire to the speed sensor that's hidden behind the xfer case shift linkage, right? I think it has two wires though? On an 89 AW4 the output shaft speed sensor is a magnetic reed switch that closes once per revolution as a magnet on the rotor passes by. You can check this with an ohmmeter (resistance). You should see it alternating between zero ohms and open circuit as you turn the output shaft. The later models (mid 96 and up) have a hall effectr sensor which does put out a/c voltage.

The engine reving up like it's in neutral doesn't sound good. A bad TCU, solenoid or wiring problem should only really cause it to shift into the wrong gear.