squealing past 2000 rpms

[most138]

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I have a strange noise coming out of my blazer. It happens when I'm under load past 2000 rpms. The sound is a very noticable squeal. The sound spools up in pitch with the engine. While going a long if I shift it in to neutral I can rev it up and make the sound also. That noise is very noticable from the inside and outside of the truck. It is not the brakes, nore the belt.
What could this be? Please help!

[Chris Stewart]

Sometimes when the serpentine belt(fan belt) gets old, it'll develope a shiny glaze on it and slips under the condition you describe. If you know the engine rpm the squeal shows up, take the belt off, start the motor while the car is parked and rev the motor to that previousily noisey rpm and see if it still squeals.....no squeal means the belt is likely bad. Also spin the pulleys to the water pump, power steering, alternator and the idler pulleys for any thing different than a dead smooth spin when you turn them.