not disagreeing with you but with a post like that you may want to explain why so people will understand it better... im also curious as to why you wouldnt want to do change it

More info here.

http://www.cygnusx1.net/Supra/TechTips/transmission_filter.aspx

well the reason its a bad idea to change old fluid if its never been changed is because the fluid gets all the dirt and junk built up and the hoses and lines expand and since automatic transmissions run by fluid pressure, the old fluid expands with the gunk build up and expands the hoses. So what happens when you replace that old gunked up expanded fluid with fresh new fluid? the transmission can build up the proper pressure to function. This is a very vague and general explanation and is probably partially incorrect, anyone else who knows more please expand on this.

All I can say Is I have always been told that if you haven't ever changed it...., Don't. Pretty much for the same reason as stated above.

Halp!
 

Hello I know this isn't in direct correlation with OP problem, but I have a prolem w/ my Transmission fluid leaking. I am a noob and just recently purchased the Supra. According to the guy who sold it to me his mechanic overfilled the Tranny with 2.5qts when in fact it should be 1.7. He told me to replace the fluid, drain the old and replace w/new. Every time I use it it creates two little puddles, the more i use the car the bigger the puddles. The leak seems to be coming from somewhere by the tranny pan but I'm not too sure. The puddles are not extremely dense and at most are the span of my extended hand, but they still worry me. So if you guys could be of some help i would greatly appreciate it!

Check the tranny oil pan gasket.

i checked the pan basket but there doesnt seem to be a problem there, but whatever is right behind (please excuse my lack of an adequate technical term) it seems to be the source of the leak since i can see some tranny fluid build up there. So I dunno :dunno:

you said that the leak looks like its coming from whatevers behind it.. with leaks its sometimes hard to pinpoint exactly where its coming from. You should purchase a couple cans of brake cleaner and clean the entire underside of the transmission very well.. drive it for a couple days then take another look and try to identify where its coming from and if it is coming from the back of the transmission, that's where the transmission connects to the driveshaft and it could be leaking from the seal.

Edit:

Any estimate on how much that would cost to repair? Supposing it was leaking from the seal?

Well, I don't know if the previous owner ever changed it, but I assumed he did since it was a nicely maintained car. I can tell he did, or tried, because I went down there and the bolt was all rounded off...so I didn't even try to get it off.
The reason I wasnted to change the tranny fluid in the first place was because whenever my car hasn't been driven for a while before going onto the highway, you have to push hard on the gas to make it shift into the next gear. The whole car "whumps." It didn't used to do this, until it sat for a year in a garage. So...I shouldn't change it? Just adding new fluid is good enough? If I'm still going to change it, I wanted to replace the drain plug, too...but I don't know where to get one that fits. This is the closest thing I could find, but it doesn't mention what size it is at all.