transmission on 2001 Buick LeSabre

while drivining the car shift hard while driving. Then, while driving, at 70 mph the rpm went to 4 and it seem as though it wasn't shifting

Asked by for the 2001 Buick LeSabre
Sounds like a transmission issue, best to have a transmission shop look into this for you. I suggest looking for an ATRA shop near you,