Torque converter or Overdrive unlocking?

[cc93cruiser]

It's happend a couple times now on the freeway at different speeds.. While cruising along in the freeway, all of the sudden the rpms jump about 200 rpms and kinda just stays there.. My reaction was to turn Overdrive button off then on, and as soon as i did this it shifted back to normal rpms... My question is it the Overdrive or the torque converter unlocking? The tranny shifts operates flawlessly otherwise 100 percent of the time... Also what could be the culprit? Gonna flush the fluid and start there....

 

[Kernal]

What year/model 80 are you driving?

 

[cc93cruiser]

1993 land crusier a442f transmission.... i dont remember what shift pattern comes first 1-3 then od and torque converter lock up, or 1-4 then T C locks up?

 

[blkprj80]

I think there is a temperature sensor that prevents TQ lockup below a certain engine temp. At least on the later years. Not sure if it will apply to yours.
Maybe you have a flaky temperature sensor? Or your OD switch might be getting dirty.

 

[cc93cruiser]

what switch (od switch) where you refering too/location? I assume that the temperature sensor would be an engine one?

 

[bigredmachine]

its the tq lock up, if it were down shifting it would be about a 1k or so rpm increase. shift pattern is 1-4 then converter lock up, 4th is the overdrive.

 

[cc93cruiser]

So, it's my od which is my 4th gear down shifting... what could be causing this all of the sudden? As mentioned it has only happend twice.. The rest of time tranny functions correctly.. Fluid appears to be clean... probably going to drop pan and rinse out filter and refill ATF

 

[cc93cruiser]

Is there a shift solenoid for Overdrive that could be at fault?

 

[Crab Sack]

Make sure that your engine temperature is warming up. If you have a stuck open thermostat it will not allow the transmission to go into overdrive due to emissions programming in the ecu. You may also notice that your interior heat is not hot if your thermostat is stuck open. You may be noticing it now that it is winter time.

 

[cc93cruiser]

You know what, I have a koso slim temp gauge I am pretty sure I noticed that it did take awhile for the temp gauge to reach 190 degrees. Once it reached that I think the thermostat opened up and the engine temp went down to the mid 180's which is what it usually operates at.. Although, it doesn't make sense, I was already in freeway with o/d and torque converter locked. This would not happen if I didn't reach correct engine temp as you described..

 

[blkprj80]

My '96 has an OD off switch by your thumb when your hand is on the shifter. Does your '93 have the same thing?

 

[cc93cruiser]

yup, 93-97's have it..

 

[blkprj80]

yup, 93-97's have it..

Does the indicator light in the dash behave when you hit the switch on and off? If so, it is possibly the temperature switch. There are two, and I don't know which affects the TQ lockup, sorry.

 

[cc93cruiser]

Do you mean that if when pressing the od button off, if I don't see the od off in the combination meter location a temperature switch can be at fault?

 

[blkprj80]

No, I mean that if you toggle the OD switch on/off, the indicator in the dash should follow the switch position.

If the button is out (off), you should see the light on the dash. I'm always hitting the damn thing with the side of my knee, so I test it often.

The light in the dash has nothing to do with the temperature switch. My comment was meant to mean that if the dash light toggles, the switch is probably good and you should look elsewhere.