Heres the problem it shifts through the gears fine til its time for overdrive. It seems to work better when the engine/trans are at operating temp. But it doesn't allways go in when it's supposed to. Warmer weather it seems to go in more often. When it actually does shift in it seems to shift pretty firm and quick like it should. Have changed fluid it is clean and filter is new. Is overdrive controled electrically or does the detent cable and vaccum control it like an old turbo trans? Any input would be greatly appreciated. THANX

 

The O/D is not supposed to engage until the fluid temp is approximately 170 degrees. In warmer weather,, that will happen sooner. After reaching operating temp, the O/D ability to kick in is determined by both ground speed and engine load. All the shifting in the A340 Series trannies is controlled by hydraulic pressure via electronic solenoids -- not by engine vacuum. For the O/D to kick in, the O/D swtich on the shifter has to be engaged ( O/D Off dash light not on). Your transmission may also have a lock-up torque converter. It, too, will not lock up until the fluid has reached operating temperature. I'm basing these assertions on the habits of my 92 model 3.0 A340H 4Runner.

Mike in AR

 

This same problem happened to me. I did just like you and had the fluid changed, still no go. I found my overdrive solenoid flaking. It's easy to fix since it is externally mounted. But before you go buy, one change your thermostat with a new Toyota brand thermostat. I remember reading up on this problem and the thermostat was the culprit alot of the times. Also I own a 2wd, 4cyl model so your tranny might be different.

 

I replaced the thermostat on my 1990 4 runner and the OD problem
that you described is better but still not fixed. No problems in the spring and summer - I only have the problem in late fall and winter when the outside temperature is cold.

 

Thanx for input will give some of these a try

 

The same thing keeps happening to me hopefully there is nothing wrong with it.