Q: Belt squeal increases with speed

asked by on March 08, 2017

I have a 2001 GMC Yukon XL SLT. A week ago my battery indicator light came on and it end up needing a new alternator 2 days after the alternator was replaced it starting making a slight squeal with an occasional chirp only noticeable when driving over 30mph took a look at the belt and pulleys and ended up replacing the drive belt because of normal wear, belt tensioner the whole assembly not just the pulley because the pulley was loose and the idler pulley had some grinding when spun freely.... the squeal has returned its quiet when idling and gets louder when driving but not while revving the engine either in park, neutral, or drive while hold brake the rest of the pulleys look and sound fine. This specific vehicle has a separate belt for the a/c and at this time its not installed otherwise I would have believed that to be the problem because it sounds the same. What am I missing and what might help fix the problem

My car has 236000 miles.
My car has an automatic transmission.

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Hi there. Usually when a belt makes the squealing sound which increases in pitch and volume with the increase in engine RPM it is due to one of two things. First, the belt may not be properly tightened or is the wrong size; or second, the pulley may not be properly aligned; causing the belt to be slightly off axis. Typically the solution to this problem is to adjust the belt tensioner and verify the pulley’s are properly installed and aligned. If you complete this step and still can’t resolve this issue, feel free to contact one of our mobile mechanics that can come to your location and help you diagnose your belt noise.

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