Toyota Repair: 1990 supra transmission (automatic), toyota supra, auto dismantler

Question
I e-mailed you earlier, but I had a seperate question about the transmission. I have a 1990 toyota supra with 200,150 or so miles on it. My dad bought it used in 93 so we've had it since then and he's done almost everything to it so he knows a lot about it. Recently maybe about 195,000 miles the transmission(automatic) started acting up. Sometimes it would get to a higher RPM before it would shift from 2nd to 3rd and sometimes it would go into some sort of neutral where he would press the gas and nothing would happen. He drives 40 miles to work through atlanta so he didn't like putting it into 2nd and driving about 40-45 in a 70 mph zone. Someone suggested to put brake fluid through the transmission for about 100 miles or so and we did that and the problem still occurs. We checked the diagnostic and nothing came up. The problems occurs worse when I have the heat on...in fact sometimes it will stop messing up when I turn the heat off. I drive it because he got a new car and my school is only 5 miles away from home and it takes about 30 or so miles before the problem occurs. Didn't know if there was anything else I can do. Would a transmission cooler help? It sounds like a heat related problem...it doesn't occur as much or as bad in the winter.  

Answer
When this kind of problem happens it is normally due to an internal transmission problem, there is an hydraulic pressure loss in the transmission, I can list all kinds of possibilities as to why this is the case but in the end the result is the same, the transmission has to be either replaced or rebuilt, I recommend replacing it with a remanufactured unit from a transmission rebuilder, if you want to save some money, you can try to locate a used transmission form a local auto dismantler, don't waste any money on a transmission cooler, it's not the problem.