AW-4 trans problem

I need some advice from those who have had to work on their AW-4.

It will not shift over 3500 RPM. If you let off the throttle, it will shift. Even then it stutters during the shift. There is a definite flat spot in every gear. It will accelerate thru the gear but applying more throttle does nothing to increase speed.

I checked the TPS. It has 83% difference in voltages. I checked two others I had also, one was 88%, the other at 84%. Is this close enough?

I also road tested it with the TCU unpluged and had the same problems with the way it shifts. This points to it being mechanical, not electrical.

The fuse in the Power Distribution Block is fine.

I had a shop look at it too. They said the TPS was fine and there where no stored codes in the ECM or TCU. They are saying the problem is mechanical in the trans. I'm starting to beleive that myself.

Does anyone have any ideas?

What year is it?

I also road tested it with the TCU unpluged and had the same problems with the way it shifts. This points to it being mechanical, not electrical.

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No that means the TCU is doing nothing...


There should be an additional fuse by the TCU... You will see it in the wiring harness that goes to it..(mind you I have an 88 and 87)

make sure the tcu is getting power.

you can also tapp into the 3 wires that control the soleniods while driving and see if they are recieving power at the right times. Only do this if the vehicle is older than a 97.

....SOL1 SOL2
1st... 12v 0v
2nd... 12v 12v
3rd.... 0v 12v
OD.... 0v 0v


solenoid #3 should get power only when the TC locks in third and od gears.

Does it have the correct tranny fluid? Dextron III is the correct one.

Have you flushed it?

RINGKONG said:

What year is it?

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It's a '93

No that means the TCU is doing nothing...

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I meant that I can eliminate the TCU being the problem. Because the shifts are still messed up with no computer input leads me toward it being mechanical. Am I missing something else that electrically controls the trans?

There should be an additional fuse by the TCU...

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I couldn't find a fuse in the harness near the TCU and the FSM doesn't show one either.

make sure the tcu is getting power.

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Well, it's not when disconnected and my problem still exists so doesn't that rule out TCU issues?

Does it have the correct tranny fluid? Dextron III is the correct one. Have you flushed it?

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It was flushed by a shop earlier this year but it's possible they used the wrong fluid. I will call them to check.

My experiance with the AW4 is that if the TCU is out of the picture... IT WILL NOT SHIFT CORRECTLY..... and the only reason it shifts is because of hydrolic pressure working the soliniods and not because they are being powered. so if you diasabled the TCU and saw no difference in shifting... then your tcu is hosed. not the other way around... but I could be wrong...


Wrong fluid and FLUSHING it will cause the symptoms you describe.

Thanks for your input Ringkong

I will have access to another TCU this weekend so I can swap it in and try it.

Can we assume you did check and readjust the throttle cable? That will affect the shift points.

Matthew Currie said:

Can we assume you did check and readjust the throttle cable? That will affect the shift points.

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Don't assume anything! Because I did not. Is this procedure outlined for me in the FSM or can you describe it for me?