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Old 02-21-2017, 10:49 PM   #1
940Texas
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Default AW71L won't shift into 4th(O/D?)

As the title says, car is a 1994 940 turbo. Also the 4th gear lockout is not active and I've tested switching it on and off with no effect.

I've already messed with the kickdown, manual I have says it should between .25 to 2mm between crimp and the cap. I've adjusted to that with no effect, even setting it full loose/full tight and several areas inbetween to no effect. Fluid looked good and at the right level when I checked, might top it off tomorrow. Any one have any other ideas at what I should look at while poking around tomorrow?
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Old 02-21-2017, 11:45 PM   #2
lverhagen
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The O/D solenoid is probably dead or its wiring has been compromised. Unless you use the car for towing, and IPD solenoid-delete plate is a cheap fix (short of actual diagnostics, but this is TB).

Ninja Edit: I realized I didn't give very much actual information. Here is my (possibly imperfect) understanding on the subject:

The O/D solenoid on the AW71 is setup up such that when it is receiving power (when the 4th gear lockout is NOT activated), then fluid is allowed to pass through an opening in the transmission itself and 4th gear can work. However, in the event that the solenoid loses power (for whatever reason, be it wiring or some other electrical gremlin) or its coil fails, then the transmission fluid is prevented from flowing.

The solenoid is useful in the event of towing or carrying heavy loads, particularly when extensive descending is involved, since you can shift the transmission into a lower gear to gain engine braking abilities.

The IPD solenoid-delete plate works by replacing the solenoid and allowing transmission fluid to flow through the 4th gear passages all the time.

I hope that helps both your understanding and your quest for real diagnostics.
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Last edited by lverhagen; 02-21-2017 at 11:54 PM..
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Old 02-22-2017, 01:50 AM   #3
ZVOLV
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Check for 12v on the wire!
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Old 02-22-2017, 02:31 AM   #4
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I got a solenoid bypass plate from my aw70 before i swapped it to sell ya if you want it
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Old 02-22-2017, 02:39 AM   #5
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I got a solenoid bypass plate from my aw70 before i swapped it to sell ya if you want it
The bypass plate works fine if you never plan on driving in mountains or tow a trailer.
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Old 02-22-2017, 11:22 AM   #6
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I would check that OD relay first.

This relay is operated by the OD pushbutton and activates the OD solenoid
If it is not working, the OD will not work.

On your car, it is on the relay board behind the ashtray.
Middle row (second from the bottom) and is the relay on the far right (passenger's side).

With the ignition switch on, the relay should click every time the OD pushbutton on the shifter is pressed.
Feel it with your hand...you should feel it click.
If no click, replace the relay

Hope this helps
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Old 02-22-2017, 11:55 AM   #7
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Quote:
Originally Posted by lverhagen View Post
The O/D solenoid is probably dead or its wiring has been compromised. Unless you use the car for towing, and IPD solenoid-delete plate is a cheap fix (short of actual diagnostics, but this is TB).

Ninja Edit: I realized I didn't give very much actual information. Here is my (possibly imperfect) understanding on the subject:

The O/D solenoid on the AW71 is setup up such that when it is receiving power (when the 4th gear lockout is NOT activated), then fluid is allowed to pass through an opening in the transmission itself and 4th gear can work. However, in the event that the solenoid loses power (for whatever reason, be it wiring or some other electrical gremlin) or its coil fails, then the transmission fluid is prevented from flowing.

The solenoid is useful in the event of towing or carrying heavy loads, particularly when extensive descending is involved, since you can shift the transmission into a lower gear to gain engine braking abilities.

The IPD solenoid-delete plate works by replacing the solenoid and allowing transmission fluid to flow through the 4th gear passages all the time.

I hope that helps both your understanding and your quest for real diagnostics.
I appreciate the detailed response as well as the other responses in here, I don't tow or drive though mountains, but I would like to keep the functionality of the lockout if possible. I wrote all the other possible problems on my clip board and I'll see what I can figure out while poking around this afternoon.

Thanks all.
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Old 02-22-2017, 12:46 PM   #8
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You don't need to spend the money on the IPD plate if your solenoid is dead. Just grind a small groove between the inner and outer rings and install without the inner o-ring, but use the outer. This accomplishes the same thing and is free.
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Old 02-22-2017, 01:45 PM   #9
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Quote:
Originally Posted by coalminer View Post
I would check that OD relay first.

This relay is operated by the OD pushbutton and activates the OD solenoid
If it is not working, the OD will not work.

On your car, it is on the relay board behind the ashtray.
Middle row (second from the bottom) and is the relay on the far right (passenger's side).

With the ignition switch on, the relay should click every time the OD pushbutton on the shifter is pressed.
Feel it with your hand...you should feel it click.
If no click, replace the relay

Hope this helps
O/D relay worked fine

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Originally Posted by lummert View Post
The bypass plate works fine if you never plan on driving in mountains or tow a trailer.
Guess I'm happy Houston is flat :^)

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Originally Posted by Wren View Post
You don't need to spend the money on the IPD plate if your solenoid is dead. Just grind a small groove between the inner and outer rings and install without the inner o-ring, but use the outer. This accomplishes the same thing and is free.
Considering I can barely work on these cars, I don't jumping into fabrication (even minor fab work) is the right answer

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Originally Posted by ZVOLV View Post
Check for 12v on the wire!
Wire had a charge, but I couldn't get a exact voltage (probably due to my idiocy)


Well it was shifting fine before I picked it up from my mechanic yesterday and none of my "even an idiot can manage this" fixes worked, so I'm just gonna bring it back and let him deal with it

If it turns out to be the solenoid I'll be sure to send you a PM esmth.

Again thank you for the helpful replies everyone.
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Old 03-01-2017, 04:51 PM   #10
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For those who might be searching this thread the solenoid delete fixed the issue.
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Old 03-01-2017, 04:58 PM   #11
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I would hope so. Only way it wouldn't would be if the OD was dead, but usually it's electrical.
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Old 03-02-2017, 04:25 PM   #12
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I would hope so. Only way it wouldn't would be if the OD was dead, but usually it's electrical.
Yeah, the wire going to the solenoid was totally destroyed and the unit itself looked like it had "boiled over"


Also of course after I put this on that heater hose under the intake manifold ruptured itself the next day...
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Old 03-02-2017, 04:40 PM   #13
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Yeah the wires in the tunnel are usually all messed up from 30 years of oil, heat, and road grime.

What do you mean boiled over looking?

I really like having control over the OD. I use the feature all the time for passing or having speed control on the freeway.

It should have 12v on it with the arrow off. I did a 740 beater recently and the customer just wanted the relay changed and no diag and we went ahead with it and his 740 was back on the road with OD after! Symptom there was the light wouldn't go out.
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Old 03-02-2017, 04:56 PM   #14
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What do you mean boiled over looking?
Where the solenoid met the transmission there was aged, coagulated trans fluid trails coming off and the o-rings were melted in. I just adjusted the kickdown so its "downshift happy" for overtaking. I would have preferred to keep the unit, but I need my daily to run and with the ignition issue I fixed and the oil pump I just had replaced I'm trying to keep costs down.
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Old 03-02-2017, 05:00 PM   #15
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Better keep an eye on the Trans fluid level. Prob should change it too. Flush it thru the cooler lines. 1 q at a time until it's clear. 12q needed approx.

The last shop I was at had a machine that would connect to the Trans lines and collect the old and add the fresh. As long as the fittings weren't a pain to find or connect it beat taking a Trans fluid shower any day trying to do a filter and Trans service.
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