acceleration on incline

[babybluet]

I have a shaking feeling in the front end of the 97 tbird when going up a hill etc. It feels exactly like driving on a rough road that has been scraped and prepared to be repaved. The shaking only last a few seconds. One person said this is a common problem in 97 Fords such as the TBird. He could not remember the name of the problem, but did remember having the transmission fluid drained and replaced along with adding an additive. This took care of the problem. Does anyone have any idea what this problem is called.

Thanks,