hey guys, lately i have been noticing a loud high pitch hum coming from under the hood. i cant tell whre its coming from or what it is. but it does it in increments of like ever second-half second on and off. and u can here it in the cab. it almsot sound like its coming from a pully, then i go listen somewhere else around the engine and it sounds like its coming from wherever ur listening. hard to pinpoit. And its only really noticable after you drive a little bit and the engine is warmed up. i dont think its the altenator... anyone have an idea of what it is? i know its hard to tell what im talking about without hearing it, i will try to get a vid if i can of it.

 

Take off the belt, and spin all of your pulleys by hand. Make sure the tensioner isn't seized as well.

 

I had that problem once and it turned out to be the fan clutch. I found it by taking a short hose and holding to my ear and just put the end on all the pulleys until I found the sound. I hope this helps in your case

 

This will make it really easy to find the noise as long as you have some stationary metal close to it that you can touch it with.
http://www.harborfreight.com/mechani...ope-41966.html

 

hey thanks for the tips guys, i listened to all the pulleys and it is definatly loudest at the altenator, but it sure doesnt sound like it when u stand on the other side of the truck. i used about a 2'-6" stick and listened to it, it ive pinpointed it to the altenator bearing. Do these go out commonly, or make a distinct noise that anyone knows of?

glad it is not the drivetrain or the fuelpump, that was my first thoughts because when i got out when the truck was running you could hear it all around the truck until i got under the hood where it was more definate

 

i picked up a new alternator today, but the only size they had that would fit within the mounts has more amps than the old one. the one i got has 300 an some amps, and the onld one said 117 amps. Im not sure, but anyone know if it matters if you run an alternator with higher amps? please let me know thanks

 

300 amps????? Are you sure? Stock, I think the largest was 136.... or some such.

No, you will not cause any problems by installing a meaner alternator. Now, in order to counter balance all those output amps, you need to install a killer stereo........

 

hey thanks for helpin man, makes me feel better. i installed it anyway lol. yea i meant 130 and some amps, not 300 sorry. now i just hope that the noise was coming from the alternator, i will find out tommorow after i drive, if its not, then i just spent 260$ on a new alternator that i didnt need. oh well. but i do think it is the bearing. if not, i dont know what else it could be. new stereo would be nice, lol

 

You need to upgrade your alternator fuse in the PDC. Your current fuse can handle the power output of the 117 but might blow with the 130ish.
Someone with the stronger alternator can tell you what the amp rating on that fuse should be.

 

Well found out that this annoying noise was not the alternator. I don't know where else it could be coming from. What about the A/C? It doesn't stay on, it just clicks on then right back off. It needs charged, but could the A/C be causing a high pitch whine noise? It does it in every gear, and it goes for like a full second, then quites for a second then whines for another second...constantly once the engine is warm. I'm stumped