Well the title pretty much says it all.

My situation: I purchased a car a month or so ago, it has a 700R4 with
everything hydraulic. Even the lock-up of the TC is hydraulically
controlled. Well, it wouldn't lock up the TC, and my friend suggested
I check the fluid level. Sure enough, it was about 3/4 of a quart low!
I filled it up to normal levels, and now it has another problem. It
won't stay in 4th gear.

If I accelerate at a normal speed up to like 60, it stays in 3rd until
I let off the gas, then drops to 4th and as long as I don't give it
much gas stays there. But the minute I give it just a little gas (not
much) it drops back down to 3rd. When I'm up around 70+, it won't even
hold 4th at just enough gas to hold cruise. It keeps dropping down to
3rd. Let alone bridges, it drops to 3rd there when it sees them a mile
away.

I really have no idea what's causing this. I thought maybe the TV
cable, so I adjusted the slider in and out and it seems to do it
either way.

Any ideas?

Thanks
-Josh