My 2007 GMC Sierra 1500 with the 5.3-liter has a particular noise from one of the rotating components that is driven off the serpentine belt. The power steering pump, tensioner, alternator, serpentine belt have been replaced but the noise continues.
When the belt is removed the noise is not present. The dealer has provided me with a TSB for my complaint. The bulletin number is 06-02-32-010A. It offers no repairs but does acknowledge the mechanical complaint is related to the power steering system.
Would a synthetic power steering fluid make a change? Is there a better quality power steering pump available?
It's a waiting game on the fix. GM Technical Service Bulletin #06-02-32-010A was published May 22, 2007, involving Chevy, GMC and Cadillac full-size 1500 series platforms. The condition is described as a low volume, high-pitched whistle noise occurring just off idle with a warm engine.
Engineers have determined that the noise is emanating from the steering gear (rack). Your noise stopped when the serpentine belt was removed from the power steering pump because pressure was no longer being applied to the gear. The TSB also states that it is a work-in-progress with no fix available at this time (but they're working on it).
I spoke directly with GMC service personnel to confirm that, as of 3-2-2009, there still has not been a follow-up service bulletin released. In the meantime, service departments have replaced steering gears to pacify customers, and it has fixed the problem, temporarily. The whistling seems to begin once a vehicle has reached about 20,000 odometer miles. So replacing the noisy rack with a new one (same part number as the original) is probably going to be a 20k mile fix -- as opposed to a modification (or modified gear) to repair the condition permanently.
Yes, it's been a while since the incomplete technical service bulletin first came out, and GM has a lot on its shoulders right now. I suggest contacting GMC customer support, maintaining friendly communication with your service department and touching base with them periodically for an update. The noise is coming from the gear, not the power steering pump, so replacing the pump is not recommended.
I've heard stories of synthetic power steering fluid helping out with typical power steering whining noises on older model GM trucks, but nothing pertaining to our mystery gear whistle. But, it would be inexpensive and couldn't hurt if you want to try it. Otherwise, turn up the radio and be patient.