I have a 1992 Toyota pickup and it will not shift into overdrive until approximately 70ish mph and I have already installed a block off plate in place of the overdrive solenoid, and nothing changed. Any ideas?

 

Which transmission? (It's on a sticker on the door pillar.)

Why would it ever shift to overdrive without an overdrive solenoid?

 

It ia an A43D

 

Wait, what?

You need the overdrive solenoid installed for the overdrive to work.

Do all of the other gears work just fine?

 

Yes, all the other gears work fine. I installed a bypass plate in place of the solenoid. So it should be just like a regular 4 speed.

 

The ECM switches the shift solenoids on and off to direct line pressure to different passages to the clutches, brakes and planetary gear sets. Different combinations of on/off determine the gear the transmission is in. I am not extremely familiar with the A43D, but I would suggest some troubleshooting.

Test the solenoid, if faulty, get a replacement.

Test the wiring to the solenoid, is it getting power during the driving conditions that require it?

I don't think deleting it is going to solve your problem.

 

It didn't, it does exactly what it was doing with the solenoid.

 

That is not surprising. The transmission has an O/D solenoid for a reason.

It is hard to help with your problem without knowing some things first...

Is the solenoid faulty? Apply battery voltage, do you hear a click? No - replace solenoid.

Is the wiring faulty? Check for continuity between the ECM solenoid wire on the ECM connector and the solenoid connector inside the transmission. If good, check for voltage at the solenoid wire when driving conditions allow shift to O/D. This can be done by connecting a multimeter to the ECM O/D solenoid pin and ground and taking the truck for a drive. When O/D is required, you should see power at that wire.

Is the ECM faulty? Wiring to solenoid good but no power supplied to solenoid when required.

If none of these things determine your problem there may be a clogged passage in the valve body. No way of knowing until you do some troubleshooting.

The attached PDF has your transmissions shift schedule.

Edit: The FSM for your truck will have the ECM wiring diagram so you can find which wire powers the O/D solenoid.

 

I want to back up for a moment.

The A43D Automatic Transmission is almost entirely hydraulically and mechanically controlled. There is no transmission computer, unlike the Four Wheel Drive A340 series Transmissions, which are computer controlled.

The A43D does not have a lockup torque converter either, just a standard torque converter.

The only electronic control the A43D has is the overdrive solenoid, which either allows the transmission to shift into overdrive or prevents the transmission to shift into overdrive.


Let's go back to the basics.

Is the Automatic Transmission Fluid up to the proper level (check it while the engine is running, preferably when the engine is all warmed up)?

Is the Automatic Transmission Fluid relatively new and does it look black or smell burnt?

Do you have a multimeter and know how to use it?

Here is the Overdrive Electric Control Circuit Diagram and testing procedure:
http://htftp.offroadsz.com/marinhake.../6overdriv.pdf

This problem could be hydraulic / mechanical and/or electrical. Using the electrical testing procedures can help narrow our focus on the problem.

 

It did the same thing with solenoid that it does with the bypass plate.

 

I went in and changed the screen and fluid because of this problem.