well thanks for looking first off, i have a 93 sc 400 and the trans seems to not like staying at 40 mph. it kinda chugs softly like the feeling when your running out of gas, the best way to decribe it is when you sit in a chair and kinda move back and forward a few inches. this only happens at 40 mph for some reason though, other than that i dont seem to have any problems with the trans, other than it feels like it needs another gear. thanks for any help

 

Start by checking the fluid level and ensuring the fluid is clean and the correct type.

 

burned ATF. That's lockup speed. Get a powerflush with Toyota T-IV ATF.