I've had this happen intermittently since I've owned this truck but right now I think its as bad as its ever been. When I start the truck cold and drive somewhere, my torque converter will lock up in OD the first time I get above ~50 mph. Once it unlocks, it will not lock up again until the next time I drive the truck. This is not a big deal on my daily commute but its killing my mileage on the highway. I got about 17 mpg on my last highway trip where I used to get between 19 and 20.

Anybody had this happen or have any idea what may cause it?

I thought the torque converter was unlocked when in OD, and only locked up when you hit the go pedal on a hill or push the button on the end of the shifter?

I may have my terminology backwards. I'll describe what I'm talking about for clarity.

Once I get above 50 mph and the revs drop, it feels like there's a direct link between the engine and transmission. In other words, I don't feel the slipping between the two that I do before that point. If my rpms increase by say 300, my speed increases by 10 mph whereas before its locked up my revs may increase with no immediate change in speed. That is caused by the slipping in the torque converter when its unlocked.

At any rate, mine's not doing what its supposed to and I can only hope its a solenoid or a problem with the valve body or something less costly than a new/rebuilt transmission. Maybe I'll try to do a manual swap if mine's on the way out. Anyone done this?

Yeah, sounds like your t/c is remaining locked. Could be a wiring gremlin, could be something far worse... Have you looked at / smelled the fluid yet?

As for swapping in a manual, 1 or 2 from this board have done it - would be basically the same as every 86-95 p/u as well. Just need to add a little more to the shopping cart. <img src="/forums/images/graemlins/smile.gif" alt="" />

Pedal assembly
Flywheel w/ hole for t/o bearing
Clutch
Seem to remember you may have to do something with the throttle position sensor as well... Could be wrong.
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Yes. I just changed the fluid a couple of months ago. The old stuff looked OK, didn't smell burnt. It had been changed about 25K miles before that by the guy I bought the truck from.

An auto to manual swap would be more complicated on these trucks than the earlier ones because the brains for the tranny are integrated into the ECU whereas on the earlier ones they were separate and worked more or less independantly.

Maybe it is a shift solenioid?There is an onboard diagnostic system for the AT.In the FSM they list trouble codes but it says that you need a Toyota hand held tester.It is possible that other hand held testers will retrieve codes but I am not sure.

That's what I was afraid of. I wonder how much and what kind of feedback the ECU looks for from the transmission. It may be possible to send it an "I'm OK" message from the transmission but I bet its just not that simple. Its too bad because the slushbox is the only thing I really dislike about my truck.

I'm going to read over the parts of the FSM that cover this. I was hoping someone else had experienced this and may be able to offer a suggestion. I'm sure any OBD II code reader would do the trick for pulling codes.

I can give you the RPM's at various speeds for my 97. I know at 70 I am turning just over 2500. Seems like that would be the only way to tell if you are locked, speed vs rpm?