Mystery trans problem please help

[grokglock]

Long story short:
I had a p0770 code
Trans died
Had it rebuilt
Code went away
Code returned 1 week later
Shop replaced new solenoids with brand new set
Code went away
Code returned
Shop replaced solenoids again
Repeat that process once again
Code goes away
Code returns...

Transmission does not display any symptoms at all. It runs and drives perfect but the code keeps popping up.

I took it to Toyota and they want me to have the trans rebuilt again with them - $5k quote.

I'm obviously not going to do that. The service advisor says the tech noted it shifted and ran like normal but they cant figure out why the code is returning and they'd have to dona full teardown to find out.

I'm stumped and frustrated. I've been driving the truck for the last month with the code on but haven't detected or felt aby abnormal driving behavior. Shifts smooth runs strong. Initially toyota said it may just be a loose connection.

Torque converter locks up and disengages at speed as normal.

My dad says his 02 tacoma has had a code since 2015 he hasnt been able to get ride of and thats his daily driver.


Should I just drive it and not worry or should O get rid of it before something worse happens?

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[audiness]

try swapping the trans computer from a junkyard truck.

 

[grokglock]

try swapping the trans computer from a junkyard truck.

I hadn't thought of that. I'm going to see of I can get one on ebay

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[rightyouareken]

If you haven't seen it already, here's the page in the FSM that relates to this code and has some troubleshooting steps.

http://www.teamtoyota4x4.org/archiv...ypdf/02rmsour/2002/024runne/di/at/cip0770.pdf

Specifically, here's what the truck thinks is happening to trigger the code:

Lock-up does not occur when driving in the lock-up range
(normal driving at 80 km/h [50 mph]), or lock-up remains ON
in the lock-up OFF range (2 trip detection logic).

 

[19963.4lsr5]

The lock up clutch is in the torque converter. If that clutch is fried the only way to fix it is to replace the torque converter. Rebuilding the trans won’t fix the TCC.


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[RotaryDreamz]

If it did so happen to be a trans issue, though it doesnt sound like it, didnt Toyota warranty it?

 

[grokglock]

The lock up clutch is in the torque converter. If that clutch is fried the only way to fix it is to replace the torque converter. Rebuilding the trans won’t fix the TCC.


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I had Toyota run a full diagnostic and they ruled out the torque converter clutch. It engages and disengages properly.

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[grokglock]

If it did so happen to be a trans issue, though it doesnt sound like it, didnt Toyota warranty it?

I had an independent shop do the rebuild. I took it to toyota to have it looked at after the CEL wouldn't go away after multiple returns to the shop that did the rebuild. I am still under warranty with them but they cant get the code to go away. Truck runs fine I commute 70 miles daily in it.

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[19963.4lsr5]

The trans will operate and shift perfectly with a problem with the TCC engagement. Did they replace your torque converter when they rebuilt your trans?

When you are driving at 60mph on a flat road and you give it more throttle does the rpm flare or slowly rise as the mph rises?


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[thegipper]

try swapping the trans computer from a junkyard truck.

There isn't a separate transmission ECU on these trucks, it's all done through the main ECU behind the glove box.

Having said that, I had a pending random misfire code that kept popping up on my 97. When I was having transmission problems (wouldn't shift out of 1st when cold), one of the things I tried doing to fix it was replacing the ECU with one from a junk yard.

While it didn't fix my transmission problem, the code has never came back since.

Moral of story, an ECU can have issues and throw codes that are not legit. I'm not saying that is what is going on with your truck, but it is a possibility.

 

[grokglock]

The trans will operate and shift perfectly with a problem with the TCC engagement. Did they replace your torque converter when they rebuilt your trans?

When you are driving at 60mph on a flat road and you give it more throttle does the rpm flare or slowly rise as the mph rises?


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If I'm going 60 and I accelerate it acts normally the rpms seem to be directly linked to the increase in mph. If I get on it hard it downshifts like normal. I can't detect anything. Toyota also ruled out any torque converter issues when they diagnosed it.

 

[SilverRidgeRunner1]

Can you confirm the valve body was gone through with the rebuild... I've been there done that with this issue.

 

[SilverRidgeRunner1]

If I'm going 60 and I accelerate it acts normally the rpms seem to be directly linked to the increase in mph. If I get on it hard it downshifts like normal. I can't detect anything. Toyota also ruled out any torque converter issues when they diagnosed it.

When I rebuild my trans had this same issue was convinced it was my ecm, and wiring. So I ran two wire from point "A" to point "B" to take the wiring harness out of the equation and replaced the ecm for the time being to see what I got issue returned next day... The final straw that had not been address was the valve body... Replaced the valve body with a reman, the issue went away instantly. . . They say u can blow air in the solenoid port to possibly dislodge the material but I had enough of the issue I was willing to do the more difficult.

 

[grokglock]

Can you confirm the valve body was gone through with the rebuild... I've been there done that with this issue.

Can you tell me more about your situation? After your rebuild did you have shifting issues or any symptoms that something was wrong?

The whole transmission was gutted and rebuilt because they found coolant in my transmission - stupid radiator design. They also added a separate trans cooler

 

[grokglock]

When I rebuild my trans had this same issue was convinced it was my ecm, and wiring. So I ran two wire from point "A" to point "B" to take the wiring harness out of the equation and replaced the ecm for the time being to see what I got issue returned next day... The final straw that had not been address was the valve body... Replaced the valve body with a reman, the issue went away instantly. . . They say u can blow air in the solenoid port to possibly dislodge the material but I had enough of the issue I was willing to do the more difficult.

I just saw this post after asking. Thanks for the info. The shop assured me that the valve body had been gone through.

 

[SilverRidgeRunner1]

I just saw this post after asking. Thanks for the info. The shop assured me that the valve body had been gone through.

No shift issue nothing just when I popped into drive and go the code came on... So if the shop is 100% on the valve body then your left with ECM and or Wiring harness

 

[thegipper]

[MENTION=97943]grokglock[/MENTION]

What year truck do you have and what trim level (auto/manual/engine)?

 

[grokglock]

When I rebuild my trans had this same issue was convinced it was my ecm, and wiring. So I ran two wire from point "A" to point "B" to take the wiring harness out of the equation and replaced the ecm for the time being to see what I got issue returned next day... The final straw that had not been address was the valve body... Replaced the valve body with a reman, the issue went away instantly. . . They say u can blow air in the solenoid port to possibly dislodge the material but I had enough of the issue I was willing to do the more difficult.

Did you replace the valve body yourself? Is it a tough job? I may try it if I can't figure anything else out.

 

[grokglock]

[MENTION=97943]grokglock[/MENTION]

What year truck do you have and what trim level (auto/manual/engine)?

97 limited 4x4 auto 6cyl

 

[dapanvid]

There isn't a separate transmission ECU on these trucks, it's all done through the main ECU behind the glove box.

Having said that, I had a pending random misfire code that kept popping up on my 97. When I was having transmission problems (wouldn't shift out of 1st when cold), one of the things I tried doing to fix it was replacing the ECU with one from a junk yard.

While it didn't fix my transmission problem, the code has never came back since.

Moral of story, an ECU can have issues and throw codes that are not legit. I'm not saying that is what is going on with your truck, but it is a possibility.

thegipper, my 98 Ltd just started not wanting to shift out of first when cold... I just ordered replacement solenoids and am planning to drop the pan and do the filter at the same time... not sure if this is the right step but I'm wondering what else you tried on yours when you were experiencing this? thanks in advance.