2004 PreRunner V6 with weird gear slip…HALP!

Good evening folks, I’ve been dealing with this issue for almost 4 months now and neither of my mechanic friends can figure out what’s going on. I have a 2004 AT PreRunner V6 with 300k on it. Back in late June, she was having a hard time finding reverse every once in a while, but didn’t seem like “a big deal”. Weeks later, she slipped out of gear to where she’d stall out at stops and was acting like she was stuck in 3rd on the highway where the thermostat would be spiking without any real signs of overheating.

I took it to my friend’s shop who works on all kinds of cars. He found a used trans with 130k on it for a great price, nice and clean from a salvage yard. She was running great for almost a month and then BAM! She started up to the same tricks where she just seemed to pop out of gear on the highway, the thermostat instantly spikes, and you can hear the gear drop down into maybe 3rd guessing on the fact that it seems to ride at 2.5rpms around 35-40. She’s also stalling out at stops and difficult to get going from a full stop as I have to rev her up.

I was talking to another knowledgeable friend the other night and he suspects some kind of sensor that’s gone bad and seems to think that it might be something with the overdrive that could be malfunctioning and if I turn off the OD that it might save me some stress for a little bit till I can get to the bottom of this.

I’ve had the thermostat changed just last week, the mechanic let it idle for something like 3hrs and took her for occasional laps around the block to see if she’d act up and he had no problems. But after I picked her up, ran some errands around town for a couple hours, she went right back to her tricks on my way home cruising around 50mph. Luckily I was able to get her home where she’s resting till I get my head wrapped around the next approach to getting this dealt with.

Whadyall got for me??? Thanks for reading and for the consistent insight you always provide!

HAPPY HALLOWS EVE!!!!

 

No codes? Have you check oil levels?