Help, New Owner of 221k milage 2009Z

[Arman080]

Thanks for the warm welcome guys. Its good to know the engine can last to such high mileage. My car's engine is extremely solid and delivers when you want it to, Which I'm very very happy about as a 19 year old. The car has never been winter driven and it's never been in an accident. The gentleman who I purchased it from had many toys and admitted to driving it hard from time to time (never tracked), But the Z has mostly highway miles, it was his daily. I did some more test driving, The car shifts up very smoothly. The problem happens when the car downshifts. There is no noise but from the inside it feels as if the car moved. It can't be just the car downshifting since its not consistent. Also when stopped the car does the same jerking motion when you go from Park to drive and vise versa. The car doesn't actually move forward or backwards, it's kind of like the car going up and down. It's probably suspension or the mounts holding the trans/engine. Quicksilver when you say service your transmission what do you mean exactly?