Oldsmobile/Buick Repair: Front End Viabration, 3800 engine, wheel balancer

Question
I have a 2001 Buick LeSabre Custom, 3800 engine, auto trans, with approx 111,000 miles.  When I accelerate between 40 and 50 MPH there is a pronounced vibration in the front wheels and steering wheel.  I have to let up on the accelerator to maintain control of the vehicle.  I was advised to repair the transmission, which was rebuilt.  Then I replaced all four tires, two front rotors, and brake pads.  It got a little better for a few days, then back to the same problem.  Below 40 MPH and above 50 MPH it rides like a dream.  Also notice a little vibration when turning (either left or right).  Your advise is truly welcomed.

Answer
Hi
I would first have the Transmission Front Mount
checked.
The one that causes problems is located low, and bolts the the cradle close to the radiator.
If it checks OK, have the rear one checked.
I would also look in your area for a shop that has a Road Force tire and wheel balancer. This machine can match balance the tires and wheels. You can check this website
http://www.gsp9700.com/
to locate one.
There are other manufactures of road force balancers..
I hope this helps.
Please follow post back, if needed.
Pawl