Pontiac Repair: Front end shimmy, power steering pump, axle shaft

Question
Mr. Puccio,
I've got a 2001 Buick LeSabre...I know you're listed under "Pontiac", but it's a general question and I hope you can help.
I noticed a bad "shimmy" in the front end, so I had a couple of balding tires replaced (the new ones installed on the front), all four tires balanced, and the alignment done.  But it still has the shimmy...mostly around 50-55 mph...then it goes away if I drive much faster.  (70 on in interstate, for example.)
During the alignment, the mechanic told me I had a leak in the power steering pump.  Could that alone cause the front-end "shimmy", or would it most likely be something else?
Any suggestions, advice you can offer are greatly appreciate.
Warm regards, and Happy Holidays!

Answer
Hi David:

This car model is very sensitive to road vibartion. any kind of tire inbalance is transmissited itno the car. I would suggest you have the tires "road force balanced" that will match the tire to the rim and get it as close to being perfectly balanced as possable. just spin blance is not good enough on these cars. Aside from that I assume all the front end parts are tight and no loose suspension parts? The only other possability would be an axle shaft that has a CV or Tripot joint going bad causing the vibration. That is VERY un likely but possable none the lesss. if all else fails there is a service bulletin out for these cars that has an updated lower control arm out for the car that has different bushings in it and that will lessen the vibartion feel transmitted it to the car. It will not eliminate it but make it better. the GM bulletin # is 00-03-10-007G. Good luck :)
Happy holidays to you as well.