93 auto has shift problems when warm

[callihn]

The vehicle has an automatic transmission and seems normal until it gets good and warm and shifts fine as far as I can remember, if I floor it the RPMs get higher ( 5000 ) and then it releases so it seems to run normal, but after a few miles of driving on the freeway everytime you touch the pedal, even slightly the RPMs go up a little higher ( +1000 ) and it sounds like it's stuck in a lower gear, flooring it no longer causes the RPMs to wind up and after stopping when you floor it then it no longer winds up the RPMs either it just goes down the road somewhat as if you were driving a manual transmission, the performance is not real bad but it sounds like it's not shifting and is hung in gear ( RPMs do not climb very high though ). I checked the fluid and it is probably two inches higher than the last marks ( actually over the turns on the stick ), but after calling a few transmission shops around town nobody seems to think that would have anything to do with it. I don't think this is considered "slipping", though it's akward and hard to explain IMHO and I really do not know what to think at this point, one person mentioned it may be that the fluid is getting thinner and bypassing things in the transmission another mentioned it may be the catalytic converter, all I know for sure is that I may go crazy and strave to death before I figure it out.

Help please?