I would not let the SEAFOAM In there forever, a few hundred to 1,000, make sure you get SEAFOAM for the trans and not the Fuel system cleaner although they are probably the same, great product though. Could also be your PCS, unfortunately the PCS along with the rest of the shift solenoids can only be changed by dropping the trana, you can drop one side of the trans while still in the car enough to get the trans side cover off, lots of videos on youtube and DIY write-ups on the internet. check out the youtube channel m ph for graet videos on dropping the trans, they are 4T65E trans though I would assume the 4T60e would be close isn't the 60 or 65 just the size of the sun gear.the "e" is electronic .