A real stumper

[mjtavares]

Ok folks. I'm at about the end of my rope here with a toyota 4runner problem, and I'm getting pretty desperate. Its a 2004, 4runner Sport Edition AWD with 84000 miles on it.

Around August of this year, my transmission started to give me problems. It would start changing at the wrong times (go from a start and directly into second or third gear), get stuck in gear (stay at fourth gear, and not go into fifth), and randomly drop out of gear and go into neutral.

Bad stuff all around.

I took it to one of my mechanics and they replaced a solenoid in the transmission. Not too bad. The problem was fixed for about a week, and then boom, it came back. I took it back and it apparently was another solenoid. At this point i'm starting to get worried. How many solenoids can they fix before it needs a new transmission? So I get it back from the shop, and the problem begins again.

So here we are now, in December, and we've just replaced the transmission. My mechanic has had transmissions specialists go over it, reps from toyota, they've reflashed the computer, looked at it with a fine tooth comb, and they are absolutely stumped. I'm stumped...stumped and pissed...and about 4k poorer. Oh yeah, and the problem is continuing, even with the new transmission installed.

Oh, and did I mention that I basically haven't driven the vehicle since december? Yeah, this thing has been in the shop more or less for the last 5 months.

Does anyone here know what the problem would be?

 

[Acidmeld]

Rough one. What codes are coming up? Have you checked all the wiring/connectors to the ecm? V6 or V8?

 

[mjtavares]

They've checked the ecm itself...I don't know if they've done a thorough wiring test on the ecm harness. I'll ask.

As of right now, there aren't any codes coming up...just the problem itself.

 

[ClockWork]

They've checked the ecm itself...I don't know if they've done a thorough wiring test on the ecm harness. I'll ask.

As of right now, there aren't any codes coming up...just the problem itself.

What engine?

 

[scojoe]

Could It be a crank sensor ? Just asking :beer:

 

[FireTruckGuy]

From just reading this, I would suspect it does not know how fast it is going. I don't know which speed sensors a 4 Runner trans relies on but I know Allison transmissions rely on input speed, middle shaft speed, and output shaft speeds to shift. In a case that the output shaft speed is off you may not see a code because it is just an input the transmission relies on. Just a thought but you may want your shop to watch you drive while they have a scan tool watching the speed sensors. A trans solenoid would only respond if it is commanded to or the output off the ecu is shorted to ground in some way. I could see this bringing on the neutral shift but cant see that you would get a positive 1-2 shift or 3-4 but at the wrong times. Has the trans ever shifted hard? Just thoughts. Keep posting your results and I am sure the guys here can have you up and running in no time.

 

[mjtavares]

Good call. I called them tonight and mentioned the speed sensor as per your recommendation...They mentioned the speed sensor, and also the shift sensor. I'll keep you guys posted.

If this turns out to be a little sensor after replacing the whole transmission...I may go a little postal.

 

[mjtavares]

V8, awd

 

[BlackWorksInc]

A little late on the train here, but sensors sound like a good option. If you've ruled out the transmission mechanially and hydraulically (which you have) and the ECM then it has to be the shift strategy itself which could be affected by skewed inputs.

Out of curiosity are there any mods on your vehicle?

 

[mjtavares]

Yeah, I'll have them look into the sensors. And nope, no mods.

You wouldn't happen to know specifically which sensors it would be?

 

[FireTruckGuy]

There was another post that was newer that the guy found corroded pins in the transmission connector. I would look close there and at the talishaft speed sensor.