It could also be the front pinion bushing as well. Mine was bad for almost 3 years until the dealership I just took it to figured it out. it took 3 dealerships and almost 3 years of unacceptable service.
2007 Sport 4.7L Bought New in Dec. of 07' w45 miles. Now has 70k+ Miles & 8 pages of Repair orders-255/65/17 Nitto Crosstek's, Flowmaster 50 SUV, A/C Delco Double Platinum copper cores, AMS Oil All the way around, K&N Air Filter, Weather Tech Floor mats, Lifetime Bumper to Bumper Warranty Exp.- 2082