[dudeyys]

I have a 1991 4runner 6 cyl 3.0 that shifts in and out of overdrive at highway speeds even at operating temp. No check engine light. I've changed my TPS and my CTS. I was almost certain it was the CTS but to no avail. Any suggestions?

[mistersnowman97]

Have you tried it in cruise? See if it makes a difference. I doubt it would, but who knows. TPS is my first guess, but I see you've already done that.
When it does shift, is it rough?

[dudeyys]

Originally Posted by mistersnowman97

Have you tried it in cruise? See if it makes a difference. I doubt it would, but who knows. TPS is my first guess, but I see you've already done that.
When it does shift, is it rough?

Yeah, same issue in cruise. When it down shifts into 4th gear the RPM's jump up to about 4000 at 70 mph as opposed to 2000 lol. And it does it randomly shifting in and out when ever it wants.

[laxbro19]

Originally Posted by dudeyys

Yeah, same issue in cruise. When it down shifts into 4th gear the RPM's jump up to about 4000 at 70 mph as opposed to 2000 lol. And it does it randomly shifting in and out when ever it wants.

4th gear is overdrive. Mine will sometimes sit at 4000 going 70 in 3rd gear and sometimes it will shift into overdrive. Doesn't matter what temp the engine is at. Interested to see what your problem is

[dudeyys]

Originally Posted by laxbro19

4th gear is overdrive. Mine will sometimes sit at 4000 going 70 in 3rd gear and sometimes it will shift into overdrive. Doesn't matter what temp the engine is at. Interested to see what your problem is

Sorry I meant it down shifts into 3rd gear randomly and back into 4th randomly. I cant speak for other years but with 2nd gens I know for certain it had to be at operating temperature before the computer will even allow it to shift in to overdrive which is why I changed my CTS. Unfortunately it was all in vain. Only thing I can think of now is replacing the overdrive solenoid. Not a cheap part so I'm open to suggestions before I buy it.

[laxbro19]

Originally Posted by dudeyys

Sorry I meant it down shifts into 3rd gear randomly and back into 4th randomly. I cant speak for other years but with 2nd gens I know for certain it had to be at operating temperature before the computer will even allow it to shift in to overdrive which is why I changed my CTS. Unfortunately it was all in vain. Only thing I can think of now is replacing the overdrive solenoid. Not a cheap part so I'm open to suggestions before I buy it.

Wish I could help you but I've got the same problem

[Outlaw wheeler 024]

Mine shifts funny like that when I pull back to drive and go into 2nd

[Buck Bridges]

Might want to check your thermostat. If it isn't working properly, your O/D will of course have issues. I replaced mine last week after having O/D issues and it fixed the problem. Saved a bunch of money as I was going to bring it to a tranny shop to diagnose.

[broken wrench]

Is this a stock truck ?

[dudeyys]

Originally Posted by broken wrench

Is this a stock truck ?

Yes its a stock truck. The only aftermarket item on it right now is the muffler. And to the other response. I already tried changing thermostat :/ this overdrive problem is seriously killing my gas mileage and the revving sometimes makes my idiot light oil temp come on. Idk maybe i gotta replace the solenoid. Its the only thing i can think of at this point. Even my neighbor who is supposedly a "master mechanic" is stumped. Its like this issue is a mystical unicorn that doesnt really exist lol

[4runnerBrett]

Replace the thermostat. Its a super cheap fix And I almost guarantee it fixes it.

[fourwd1]

That's what can happen when the O/D solenoid starts going south.

[broken wrench]

have you done the diagnostic code flash with OD light , is your light blinking ?

[dudeyys]

Originally Posted by broken wrench

have you done the diagnostic code flash with OD light , is your light blinking ?

Not yet i have an obd2 but not an obd1 lol. No the o/d light stays off when i have the button toggled on.

[broken wrench]

There is still a trans diagnostic that you can run ,get an fsm . But if your light isn't blinking then most likely its not any soleniods but burnt clutchs