08 type-s AT at 123k miles and my transmission is starting to act up. When going into 3rd my rpm’s suddenly go up a bit and the car jerks a bit. When stepping on the throttle to accelerate the car downshifts hard and shakes violently almost as if I hit something before beginning to accelerate. I have done a 3x3 ATF flush as well as a separate ATF change recently. I plan on switching my 3rd and 4th gear pressure switches in hopes that it solves the issue.

 

When I purchased the car the tranny drained very low fluid (maybe only a quart and a half) and was extremely black. I hope my tranny isn’t shot.

 

Draining only a quart and a half of cooked fluid makes me think the damage has already been done. It's very important to check stuff like that when purchasing a car, I feel like it wouldn't have even registered fluid on the trans dipstick in which case.

Pressure switches might be a long shot, but if it's only occurring in that range of gearing, you might get lucky.