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AW4 Shifting Issues


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The past few weeks the AW4 in Deb's '88 has not been acting well. It only acts up intermittently. Some days it is fine, others not.

 

Symptoms:

* Sticks in a gear and won't up shift

* Seems to get confused and can't figure out which gear it wants to be in

* Almost seems like the torque converter will unlock and the engine will rev

 

I've never actually experienced a slipping transmission, so it is quite possible that the last symptom is just that and I don't know enough to realize it.

 

Since it doesn't do it all the time, my first thought is that it is something electrical. This is the electrical trouble shooting I have performed:

* Replaced the transmission computer

* Tested the voltage output of the TPS

 

These are the electrical things I am trying to figure out if they could be causing these issues:

* Solenoids

* Speed Sensor

* Wiring

 

I changed the fluid a couple of weeks ago and everything actually looked really good. The old filter looked great and the magnets only had the expected metallic film. No chunks or burnt fluid. I also adjusted the throttle cable.

 

I swapped this transmission into this MJ about 2 1/2 years ago. I have really never been happy with the way it shifted. It upshifts at 2500 RPM no matter how much you are on the throttle. The torque converter locks up immediately after you hit third gear, causing it to bog down. I thought the most likely cause of this would be a faulty TPS reading, but it checks out fine.

 

Can anybody point me to what may be causing this? Does this sound like an electrical or mechanical problem?

 

Thanks,

Willy

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........

I swapped this transmission into this MJ about 2 1/2 years ago. I have really never been happy with the way it shifted. It upshifts at 2500 RPM no matter how much you are on the throttle. The torque converter locks up immediately after you hit third gear, causing it to bog down. I thought the most likely cause of this would be a faulty TPS reading, but it checks out fine.

 

Until this last paragraph, I would have suggested that you inspect the brake switch and it's associated wiring. Now, I'm not so sure BUT it wouldn't hurt to check anyways (well if you're flexible it won't hurt, too much, probably, maybe).

 

Scott

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First place I would check with a misbehaving AW-4 is the TPS. You said you checked it, but if the trans is only acting up intermittently, then the TPS may be acting up intermittently. Do you have another TB with an adjusted TPS you could swap on for awhile?

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Unplug the TCU and drive it, if it doesn't act up then it's electrical. You'll need to manually shift it and won't have second gear (1-2 = 1st, 3 = 3rd, D = overdrive/4th when TCU is unplugged)

 

Divide and conquer!

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Unplug the TCU and drive it, if it doesn't act up then it's electrical. You'll need to manually shift it and won't have second gear (1-2 = 1st, 3 = 3rd, D = overdrive/4th when TCU is unplugged)

 

Divide and conquer!

 

Good idea. I've even got a switch that shuts off the power to the TCU that will make this easy.

 

Thanks,

Willy

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Does anybody have a wiring diagram that shows all the transmission wiring? I've got a FSM but it is missing a couple of the wires in the gray harness.

 

I need help with these two in the gray harness:

* Location A - yellow with a black stripe. The TCU also has a yellow with black stripe wire that my FSM identifies as going to the diagnostic port. Is this one also a diagnostic wire?

* Location H - black with a red stripe. My best guess is this goes from the NSS to the ignition to prevent starting in gear.

 

Can anybody verify what these wires are for?

 

Thanks,

Willy

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