4x4ToyotaFarm

We have 4 yotas all 85-89's- My 89 4runner v63.0L AT has an issue with the over drive. 263,000miles- only problem is irratic function of the OD.? The OD works when it feels like it- shifts in and out of OD with no pattern. Sometimes it works perfectly, other times never works, and sometimes it goes in and out of overdrive as it chooses. Does not have a pattern- underload, not underload, cold, warm, excellerating, deselleration, steady speed, it has reacted irratically under all driving conditions and is not consistant with working or not working in any situation.?? OD switch works for on/off ..IF it decides to be in overdrive. Heard about shorts in wiring near steering pump as poss cause????? Tranny great shape, shifts smooth, just eating up the gas with no OD and racking my brain about poss cause. Been like this for about a year- more frequent when cold out- thermostat seems to be working fine though. Just got check engine code this morning though- CODE 25, 26, and 51. Any thoughts on where to start? Thinkin o2 sensor for 25-26. CODE 51 is a new one for me. ECU? A/C wiring from power steering pump shorted??? HELP?

4rnr

not sure of the cause, but AWshifting.com has nice little sytems to manually control all functions of the tranny. Im sure you could wire in to the harnes and control the TC with a switch/button whatever.

4runnerx3

Unplug the control unit for the tranny and manual shift. 1 is first, 2 is drive and D is overdrive. You will not have 3rd because of the shift solenoids are not working. This will let you know if you have an electrical problem.

4x4ToyotaFarm

Just wanna say thanks for the two replies I have recieved so far about my OD issues. AWshifting.com is awesome site, and definately would solve OD probs! Going to try unplugging to check for electrical probs first thing tomorrow. Keep advise coming, and I will let ya know if I solve the problem. This is one chick that isn't given up on her 4runner! -

scab

I've had the same problem for about a year.

From everything I've read, my best guess is bad thermostat in my case. If tstat is sticking open, and the car never gets fully warmed up, the computer will not allow the tranny to engage OD.

My temp guage needle stays on the left half most of the time.

I'm planning to go by the dealership and pick up a new tstat and see if that fixes it. I'll let you know if it does.

Please post your results as well.

scab

I changed the thermostat, took it out for a test run, and the OD works fine again... engaged before I hit the end of my street (about a mile @ 45mph+).

It's nice to go down the highway at 2500rpm instead of 4000+.

mt_goat

Last I heard that shift controller would constantly throw CELs, did they ever come up with a fix for that?

4x4ToyotaFarm

update- I unplugged the control unit from the tranny and am manually shifting. Shifts great now and OD working perfectly. Any advice on how to proceed with locating the electrical issue my Runner must have?

In regards to thermostat fix scab posted - My temp seems to always read the same- zero at start and just less than half at all operating times. No inbetweens and never even middle on guage. Are you still getting consistant shifting into OD? Might throw in new thermostat anyway since so inexpensive.

Keep those Runners rollin- and any advice is awesome -Mrs 4x4ToyotaFarmer