Strange "shudder"?

[woodly1069]

Seeing how I'm new to the whole Mustang thing, I figured I would try to get a few answers for my new ride. I just purchased a 2001 GT convertible with a 5 speed and I LOVE it! This has already got to be my favorite car; it just wants to be driven. I took her out for a little trip this weekend and it did pretty well. I did notice that I seem to have a problem while out on the interstate, the car wants to "shudder" like an auto with a torque converter problem. It only seems to happen at a certain throttle position; somewhere in the middle while under a decent load. I did notice that it will do it in other gears so I don't believe it is in the transmission. If anyone has any comments I'd lobe to hear them. Thanks in advance for any input!

[lowering kit]

had a similar problem that seemed to be the converter and changing the fluid fixed it.
i would check the fluid, should be redish, not dark, not smell burnt.

[SpectorV]

change the fluid EVERY YEAR if you have not changed it in a while or you are not sure when it has been changed drain the tq converter as well as drain the valve body/pan.

it might also be tire related. If it does it mainly in a mph range then its an out of balance issue.