Was changing ATF on my daily driver and I think the automatic transmission may be now in limp mode or something. Car is now in 1st gear and won't shift up. At first, the gears were shifting after the ATF change, then when I had to drive the car a little harder to pass someone, the car went and got stuck in 1st. I didn't fully tighten the tranny pan so maybe that caused this? I also changed transmission filter.

This is a 1988 Buick Park Ave w 134k mi.

I disconnected battery for 6 hrs and steped on brake in hope of resetting tranny ecu. Still stuck in 1st. Any ideas??

The transmission in car is a 4T60, non electronic. It has a modulator, Governor, and TV cable that controls shift timing.

The TV cable plunger is probably stuck, a common problem. With the hood open while standing at the drives side fender, look down at the transmission; that is were you will find the TV cable, a black plastic housing with a 10 mm bolt, bolted to the transmission. Take the air cleaner off and trace the cable up to the linkage, grab the steel cable and pull up on it, you should feel resistance, and release it, the cable should SPRING BACK. If the cable feels lose, the TV plunger is stuck, if so, buy a bottle of lube guard for sticking valves. Pour it into the transmission and let it circulate. With the engine hot try pulling on the cable too free it. If you can not free the cable the valve body has to be removed. Good luck.

Put in a $2 transmission pour in bottle and that put a stop to the shudder and shift issue. Amazing what $2 can do!!