[1999montana]

While my experience has not been as severe as what you describe, the trans did begin to show signs of hard shifting (mostly when the trans and engine got hot due to higher ambient temperatures).

I finally did two things that have stopped this problem and seem to have given the trans new life at about 170,000 Kms.

The first step was to drop the pan and remove the filter. The inside of the pan had a lot of grey film, but no pieces or particles. I attributed the film to the normal action of the bands and clutches, combined with the torque converter slipping (it’s designed to do this apparently during lock-up). In other words, normal wear and tear.

Then, I removed the accumulator assembly, cleaned it, lubing the two servos with clean trans fluid. Installed a shift kit from ZZPerformance.com for the 4T65E series transmission, following the instructions and using the recommended spacers. Added a new filter and buttoned it back up. Then installed a trans cooler that should drop the operating temperature (regardless of season).

Added a 947 ml bottle of Lucas trans conditioner (stuff comes out looking like STP!!) and filled the trans with new Dexron fluid. Made a huge difference. Nice crisp shifts between 1st and 2nd and a firm 3rd to overdrive change too.

Total cost: about $10 for the Lucas, and $30 for the shift kit.