i have a 2000 bonneville sle just changed both mounts and the trans still shifts with a jerk after about 10-15 minutes of driving.

Did you check this out Transmission Trouble Shooting Guide here https://www.gmforum.com/t279700/

Whats the outside temp. when your driving?

Try jacking up the front of the car and checking for any play in the front end. Rotate the tires while in neutral and watch the other tire. Is there slop there? If so, watch each joint and track down the slop. Is it at the joint or inside the transmission? Make sure you have jack stands.

Is it a really light surging that is barely noticable or hard jerk felt in every shift?

the temp is 30'* but it does it after the car warms up and its a aggressive jerk at every shift and i did change trans fluid about a month and a half ago.

Sounds like a Pressure Control Solenoid. I'd have someone knowledgable with tranny'* confirm.

I have the same problem

i'm not sure what it is but i'm gonna find out. my friend has a 05 grand prix with a 3.8 and he also has the same problem.

Let me know what your find out Vader