2001 Toyota 4Runner SR5 4WD

Issue : Popped these codes PO773 and P1780

Nothing happened for awhile and then when it started getting hot out the SUV would make some heavy clunking which you could feel while driving and then slip out of gear. When that happened the RPMs would rev up being out of gear. I pulled over and was able to limp it home in 1st gear. If I tried to go any faster it would slip out of gear again. The next day when it was cold in the morning I had no issues. Drove it to work. Then it sat in the hot sun all day and the original issue happened again.

So I researched the codes and figured it had to be P0773 which is the TCM ( transmission control module). I ordered a new one and replaced it. The same exact thing is happening. I noticed two more solenoids located next to the TCM when I dropped the tranny pan. I should’ve replaced those as well but I figured I would ask everyone in here their thoughts before I drop the pan again.

The P1780 error is a park/neutral switch code. This kind of makes sense because if I am driving and the car thinks its in neutral it would slip out of gear and the RPMs woukd go up. But then if I slow down why would that reset it and allow me to drive in first at lower RPMs?

On a side not. On the dash the VSC OFF and VSC Trac lights have been on for awhile as well.

Any information helping me solve this issue would greatly be appreciated! If I can provide any more information please let me know. I am desperate to figure this out. Sucks asking for rides everyday! Thank you.

P1780 code is for the park/neutral switch which is part of the engine starting system so not relevant to your transmission problem.

P0773 code is for shift solenoid e. This can be caused by shift solenoids e failing or the torque converter failing. What condition is your transmission fluid? Is it black and smell burnt? Is your fluid level at the correct level?

You can try changing the shift solenoids, but most likely your torque converter has failed.

The fluid was a good color. I replaced shift solenoid e to no avail. Is the torque converter a big project? I will look into it now. I am learning as I go. Thanks for your reply.

Also, this transmission is relatively new.

yep, torque converter is a big job. Have to drop transmission out. if I was dong that I would take a hard look at flex plate too as they can develop cracks and be an issue...its behind torque converter.

You've tried the easy fix, unfortunately. I also agree that it sounds like a failed torque convertor but hard to say without driving it. The torque converter is a large circular 'doughnut' that sits between the engine output shaft and the transmission and 'converts' the power leaving the engine. If the part fails (it's 100% mechanical) then the transmission has a hard time shifting and controlling engine RPM as it shifts gears.

Any idea if the shop that installed the new transmission also replaced the torque converter? If yes they should provide a warranty. At the very least, you could bring the vehicle back to them if they warranty any of their labor.

Is there a chance the selector switch and/or shift linkage isn’t adjusted correctly? I’ve seen many techs replace a transmission and cause funky things when they’re done because they didn’t make sure the physical shaft matched the correct gear’s detent.

It could be possible the actual shaft is between drive/neutral when the cluster read “D” or something. Should be an Easy thing the adjust and costs $0

Adding appropriate music for the title of the thread

https://www.youtube.com/watch?v=JnOeIFx3ML8&t=3