2008 Yukon pulley noise

[Denali Z]

High pitched whining from the front belt area. Had alternator tested, test came back good. I am planning on replacing the idler/tensioner pulleys but curious if I can replace just the pulley on the alternator? Every part store in my area does not sell one and have to buy the full alternator. Any ideas or help would be appreciated.

 

[B-train]

The pulley wouldn't likely cause the noise unless it is grooved wrong, or not installed at the right alignment for the belt track. If it is a noisy alternator, it's most likely bearing noise and probably should just be replaced.

You can drop the belt off and spin the pulleys by hand to see what they sound like. Any dry or gravely noise is indicative of a bearing that is either worn, dry of grease, or both.

Sealed bearings can be regeased FYI (tensioner, idler). Remove from truck, pull out one side of bearing (flat seal) with a pick, wash with brake clean, blow out dry, pack with new grease, and reassemble. It's a cheap DIY fix you can try if you find a noisy one.

 

[Geotrash]

High pitched whining from the front belt area. Had alternator tested, test came back good. I am planning on replacing the idler/tensioner pulleys but curious if I can replace just the pulley on the alternator? Every part store in my area does not sell one and have to buy the full alternator. Any ideas or help would be appreciated.

A mechanic's stethoscope costs $20 and is worth its weight in gold for this kind of thing. Note also that some rebuilt alternators do make a high pitched whining noise. I had one like that on my '07 when I bought it, which eventually failed though it wasn't the bearings. I replaced it with a new unit and the problem was gone.

Chances are though that it's a pulley on either the belt tensioner or the idler. I consider it routine maintenance to replace all tensioners and idler pulleys every 100K miles or less, which also happens to be the belt replacement interval. You can buy good replacements at rockauto.com