i think its the transmission..not sure..but..when i drive the car slow and get around 30-50mph i heard a grundling sound. u can feel it and hear it. its a pretty deep grundle noise. its got 126,000 miles on it. if u drive the car fast u barely hear it or sometimes dont hear or feel.

 

My car did the same thing between 35mph-50mph. The A/T would shudder and sound like it was kinda grinding. Go to www.alldata.com for recall and the APR 1998 service bulletin address's it. You will have to completely change out your A/T fluid (bone dry) and replace it. If you look up that service bullentin it will explain what has to be done. My car hasn't done it since