What is the whirring sound in my 96 GMC 3/4 ton Sierra with a 350?

[tjkayaker]

I already changed the belt pulley, belt tensioner, and the power steering pump. Seems like it is from the front on the engine.

 

[Molson02536]

I already changed the belt pulley, belt tensioner, and the power steering pump. Seems like it is from the front on the engine.

Try removing your serpentine belt and run the engine to see if the noise goes away, if it does then most likely the bearing on your alternator has gone bad and will need to be replaced. If the noise is still there , inspect your transmission fluid to make sure it's at the right operating leave. There should not be any sign of fluid foaming or burnt transmission fluid.

If there is a whirring sound get's loader when the transmission is placed in gear, there may be a good chance that your transmission pump has gone bad and will need to be replaced. If your lucky, the transmission oil filter has fallen from the valve body and is picking up air causing your front transmission pump to make the noise.

As mentioned if the nose goes away with the belt off and running, good chance that the noise is from your alternator. With the engine not running you can check the alternator but just turning the pulley and feeling for play or any hesitation as your turn the pulley on the alternator.

Good luck and keep us posted.