[Monkey]

have you ever changed the transmission fluid? Try getting a full flush and see if that helps. You might have something moving in there that isnt. While under there, either yourself or your mechanic, check the rear seal (where the driveshaft goes into the tranny) to make sure it's not leaking.

I'm also moving this to Suspension and Drivetrain since this is a drivetrain issue

 

[Monkey]

just get yokohomos. I had them and they are a bit wider than the factory ones, but for 15" tires, you can't get really great performance tires.

is it shaking any when you press on the brakes? you might need your rotors turned too

 

[Monkey]

ask again in the v6tech section. just keep this thread about suspension or drivetrain.