shifting problems

[ApullinV6]

I just changed the trans. fluid and filter yesterday. Went to town today everthing was doing fine. On the way back home the car started shifting funny. It would shift through the gears before I would even get up to around 30-40 mph. Then when I slowed down it wouldn't shift down like it's suppose to.
Any body know what the problem might be.

 

[ApullinV6]

some more info.

The trans. shifted ok before, kinda sluggish when hot. I was told that type F trans. fluid would firm up the shifts and also make it run cooler.
I also checked the detent. cable and it seems to be fine.

 

[ApullinV6]

Took car out today and tran. shifted fine at first. Almost made it back to the house when it done it again. Started short shifting and also not downshifting.
A friend of mine told me to jack the car up and bring car up to cruising speed, then go under hood and pull det. cable. That this might open up the valve? and let any trash go through.

Any body got any ideas??