Need help IDing a sound.

[KYEdge]

Well, I'm pretty certain it is a bearing going out; it sounds dead up like the rattling screech that a bearing makes when it starts to fail. The problem is I can't figure out what bearing.

It will not do it with the truck in park or neutral and just revving the engine. If I do that the engine sounds perfectly fine.

It will only do it while moving, and seems to manifest itself the most when accelerating above 40mph. RPMs don't seem to be a factor in it starting (just the speed, mainly increasing speed) but the RPMs DO seem to change how fast it sounds like its spinning.

The noise fades away a few seconds after I reach a steady speed, but will come back anytime I blip the throttle or speed up a few miles per hour; then once everything is steady again it fades away. This of course is confusing the crap out of me. I can go rev it in the driveway to 2500 RPMs and it sounds healthy; but I pull out onto the road and start accelerating away at 2500 RPMs it starts to squeal right around 40mph. Once I hit a steady speed say around 55 or 60 and it goes away I can blip the throttle and it comes back, but if I don't keep the throttle down to actually accelerate the noise just fades away again.

I can't even really pin point the general location of where it comes from since I'm in a moving truck. I think it seems to be coming from somewhere near the front of the engine bay on the passenger side (ie maybe around the alternator area).

I have no idea if it is the speed that causes it and the RPMs just go up as the speed goes up so that is just a coincidence; or if it is the RPMs that cause it and the speed just goes up when the RPMs go up.

 

[Viper Command]

Could be the cam syncro.

 

[KYEdge]

That was replaced about a year and half ago. I remember that being pretty much a constant sound that varied with the RPMs but could always be heard with the engine running.

 

[Cody Ray]

There are a couple things you can check first that are far easier to check. Both belts and torque converts can make bearing sounds. Give the belt a spray of appropriate lube and go for a drive. If the sound stops you will need to replace the belt as it is worn. A cracked torque converter will more than likely leave oil on the driveway. Of course if it is manual ignore that last bit.

 

[Ditchbanger]

funny noises

My alternator was doing the same thing. Made some real bad noises for about two weeks before it seized up in the Carquest parking lot. Id check that.