SinCityFX4

On your pulley's?

California

rent a pulley puller from autozone for free, and just replace the pulley. they are cheap

Ron Croxell

My high pitch whistle at 1800 rpms when cold was coming from my alternator bearings. New alternator no whistle.

Coner

How much was a new alternator?

jamie930

I have this whistle also but only when it is cold and after the engine is up to temp and been a highway speeds for 15 min or so. It varies will the engine speed.
The question have is how many people have the aux trans cooler?

As the trans comes to temp the cooler is bypassed. I think this whistle is from the cooler bypass valve just cracking open. Hence only when cold and after it is up to temp and been driving 15-20 min

Keith4585

Hi everyone
This problem in engine from xc side here is a whistling, loud sound coming from under hood in my XC 2001. Will this be costly to fix.

j air

My 06 with a 5.4L had a high pitch whistle or ring that only occurred in cold weather. Came and went with power changes, I replaced the idler puller below and left ( as seated in the truck) of the alternator. The noise went away. The steel outer race of the bearing was slipping on the aluminum hub it was mounted on. Worth checking.

bgris

which bearings?

bgris

can vary from 125 to 200. They are really easy to do it your self. I personally recomend getting an upgraded alternator if your running aux lights or an upgraded radio with subs and all that good stuff.

Floored150

Any suggestions on where to buy and what to look for. Just do a search for upgraded alternator for F150 (year)?