2007 Tacoma, odd automatic transmission behavior

I put the Magnuson supercharger on my engine at 90k, changed the transmission fluid and did a valve body upgrade all at the same time. Followed the instructions on how to change the fluid. Life was good until about 110k. I'm at 112k now and for the past couple thousand when the transmission shifts between 4th and 5th gears, the RPMs will rise to around 3k before dropping down into 5th gear. This happens randomly. I changed the fluid again to verify that the level was correct, and it was. No change. If I'm driving on a slight uphill, it won't upshift even though it's in a low load condition. Once I go to a slight downhill, it'll upshift. On flat ground, sometimes it will upshift normally, other times it revs up.

What are the possible causes of this, and solutions?

 

So....bump?

 

@gearcruncher

 

I think your best bet is a lab scope or real time scanner to diagnose this followed by checking pressures
Because this transmission is completely computer controlled , you have to start with the basics .
The issue is too intermittant to set a code .
Did Magnuson supply you with a tune for the engine and transmission or you running the dealer supercharged tune ?

 

First I was on the UCON. No issues. Then I flashed to the TRD factory tune with the OVTune on top. Issues. Revert to TRD. Issues. Never used the Magnuson Bully Dog. OV Tune says they left the TRD transmission coding intact.

 

Assuming you are checking the trans fluid with the truck running , I am steering towards a pressure control problem possibly with your throttle position sensor but this could be the end result of the issue , not the beginning .
Just to be sure , have you scanned for codes ? at this point I am only guessing as there are hundreds of possibilities
In other words an intermittant glitch causing the transmission to think you have your foot to the floor . As soon as you begin to drive down hill , you ease off the gas pedal to maintain the speed limit and the transmission upshifts to 5th .
If you have a real time scanner , you can press the movie feature when you experience the glitch and the scanner will record all the information the computer controls such as the TPS are sending to the transmission ecu

 

Yep, checking the trans with engine running and at temp according to the dash light flashing method.

I'll scan for codes, but there's no check engine light thus far.

 

I have been involved with a few members here at TW who use this
https://www.tacomaworld.com/threads/hp-tuners-for-2005-2015.600793/
They say this is an excellent product to tune as well as monitor computer commands .

 

Went by my local trusted auto trans shop, and they confirmed it is flaring between 4-5, but not bad enough to warrant a rebuild yet. He said I might get 2-3 more years out of it, but I'm going to start budgeting a heavy duty rebuild later this year.