I bought a 1989 GMC sierra SLE a week ago and I have been stumped on it ever since. Its a 350 tbi 5 speed with a six inch lift and 35" mud tires. There is this loud whining while running and I am out of ideas. At first I thought it was the alt bearing, so I swapped alts and its still whining....anyone have any ideas?

 

Mud tires will do it too I seen a tire get a chip off and screem

 

Its not my tires, it whines will parked with the engine on. Besides I have run mud tires on every one of my trucks, and I have never had them scream, they do have a fair bit of road whine, but thats due to the aggressive tread.

 

What about the belts, idlers and or tensioners?

 

is it a high pitch whine or like a groaning sound

 

Take the belt off and start it, does it still make the noise?

 

Its a groaning. I have been driving it to work and it drives fine, which is why im stumped.

 

could be a bearing for a pulley starting to go