I had a leak on the transmission dipstick tube at the bottom where it connects to the transmission housing. I replaced the o-ring and replaced the transmission fluid , gasket and filter at the same time. - Leak solved

However, after replacement of o-ring and fluid i noticed a couple of things:
1. No kickdown when gas pedal is floored and kickdown switch is engaged. also noticed that gear changes erratically from 3rd to 4th. Gear changes normally when done manually.
2. when coming to a stop i notice there is a thud (not severe but noticeable) which tells me gear change to 1st. (Could this be a modulator problem)

I am at a loss thinking maybe I had accidentally touched or moved something in the valve body while changing the filter?

At any rate I did some troubleshooting and everything so far tested good. Here is what i did:
1. Bench tested kickdown switch - NC/NO contacts good
2. Resistance measurement at solenoid is 13.6 ohms
3. measured voltage at solenoid wire (after disconnecting wire) while flooring gas pedal - good at 12 volts
4. Applied +12V from battery to solenoid and could hear a click - to me this means solenoid is good. (or is it?)
5. Also replaced fuel pump relay (as some in forum have suggested) - problem still exist
6. Inspected bowden cable - no binding there

Problem persist even after all the testing above. Let me know if you guys have any other ideas. Thanks