kt19

I have a 90 Pickup with a 3.0 and auto tranny (A340F). The transmission will shift out of Overdrive into 3rd after a short period of driving. It will be in the higher side of 3rd (maybe full lock up?) and will stay there for an undetermined amout of time and is never the same. It only does is when driving for a short period of time with little to no load on the engine. After reading a few threads I think that it may be the overdrive selinoid. I'm not sure so any help would be greatly appriciated.

regularguy412

Check your fluid and make sure it is not overfilled or underfilled. Make sure the engine / transmission are completely up to operating temperature. Then check on level ground with the tranny in neutral , engine idling. If overfull, you may have a foaming problem.

Mike in AR

kt19

The fluid is at proper level and I just changed it and added a pint of Trans X, so that is not causing me any issues due to under or over filled. It was doing this before I changed the fluid and it continues to happen more often than before.
Thank You

regularguy412

Make sure the shift linkage is properly adjusted. There is 'play' in mine after 183,000 miles. Even with the linkage properly adjusted, the shifting is erratic, if I don't get it EXACTLY into the D slot.

Your transmission also has a locking torque converter. It, too, has a solenoid that controls the converter lock-up. Don't be confused by the converter locking / unlocking under varying engine loads and road conditions (read: climbing hills). This is different from the transmission shifting out of O/D. It is normal for the converter to do that. Try clicking the O/D Off (switch is on the shifter on my 92) and see if you still get similar symptoms in 3rd gear instead of the O/D gear.

Be aware that the auto trannies have a fluid temperature switch. The transmission is designed NOT to shift into O/D even with the O/D switch ON until the fluid temp reaches approximately 170 degrees fahrenheit. The converter also will not lock up until the appropritate fluid temp is reached.

Mike in AR

kt19

Do you think that maybe the temp switch is bad? It will always act up with no load on the engine usually on a slight decline. I have tried a little wiggle of the gear selector when the problems presents itself and have turned off the o/d switch and on then off and so on with no change. When the truck goes back into O/D it will shift normal and will be fine untill another slight decline.
Could it be something to do with the accelerator cable atteched to the transmission, (The Kick down cable.) Also this will only happen after it has gone into O/D and is at operating tempature. Probably the best way to describe the operating characteristic of the transmission when the problem occurs is the same as when the truck is not at operating tempature. This makes me think that it may be something to do with a temp sensor.
I appreciate your help I have got nothing from the dealerships around here except that they would be glad to put a new tranny in for me.
A guy at a transmission shop suggested the Kick down cable and another person thought a selinoid, and my chilton manual sucks.
Thanks again

JamesD

My 89 does pretty much the same thing except it does it when the O/D button is off as well. I'am thinking TC lockup solenoid. Please link me on where it is and how to if anyone knows. I will search as well.

Thanks, James

4Runner 4Play

I also had that problem with my 93 Runner a while back. I found out that with my cooling system, the thermostat will control whether the O.D. can be used or not. If the thermo is faulty, your'e truck will never reach operating temp. Soooo.... because it wont reach the right temp, the O.D. wont be able to engage. You might find ,as I did, that it will shift in and out of O.D. because the thermo will open up as it gets warm, and then shut back off again as you keep on driving thus cooling the engine. Soooo, I think Its the thermo. I might be wrong, but that rarely happens... lol
Hope this help you!!
Cheers, Lee Hathaway

regularguy412

Hmmmm. Could be temp related. So you can test the engine temp sensor and the tranny fluid temp sensor(s) -- ( I believe there are two of them ).

ALSO,, believe it or not,, check your TPS (Throttle Position Sensor) on the throttle body. It may not be working properly, or more likely , not adjusted properly. The tranny ECM looks to the TPS to help make decisions about what shifting to perform.

Mike in AR

kt19

Thanks for all of your help. I leaning towards the temp issue but it seems that my gauge for the engine stays pretty constant so possibly the one for the tranny. Does any one know where that is located, is external or internal, and should I buy from the dealer or aftermarket.

regularguy412

Look here and scroll down a little for electronic sensor locations:

http://personal.utulsa.edu/~nathan-b...48electron.pdf

Be aware that the engine temp gauge is not super accurate. Also on my A340H, the tranny temp seems to lag a little behind the engine temp. That is: the tranny doesn't reach operating temp and hit O/D or Converter Lockup until a couple minutes AFTER the engine temp gauge stabilizes at 'normal' ( near the center of the gauge).

I'm not aware of quality issues with either the aftermarket or dealer sensors. I have seen them advertised on the major chain parts stores sites.

MIke in AR