Noise while in drive and reverse

[sunfish32]

I have a 2000 Excursion with a PSD auto and a few mods (banks big head, trans command and western turbo brake). I am not super familiar with all mods since i bought the truck with all mods in place. Anyway the other day i started hearing a noise while the truck is in either reverse or drive when either my foot is on the brake and when accellerating from stopped. I have tried to pinpoint where its coming from and it appears to be louder under the truck. The noise is sort of a whine or whistle possibly like a bearing has worn out. There is no noise in when in park idling and it has no vibration. I searched the forums for insight and people have mentioned somewhat similar noises with the EBPV on the turbo but I would assume that i would have sluggishness or boost issues associated and i really haven't noticed that.
Any help would be appreciated.
MIKE

[o0firemaster0o]

First off Welcome to the ORG! Does the sound speed up with the motor? I would check to make sure its not your belt slipping or your power steering pump. Theres other things that could be to this also. Me, I would also jack the truck up and start spinning wheels to make sure its not wheel bearings or brakes. Then start the vehicle while up on jack stands and see what it does.

[sunfish32]

Thanks for the reply firemaster. The noise happens only in drive and reverse moving and not moving. In Park it is quiet. It does not get louder with speed in fact it seems to go away under heavy pedal pressure. I can hear it when cruising under light accellerater pressure. While moving, the noise of the engine tends to mask the whine. I have a new serpentine belt and it doesnt seem to be related to power steering cause there is no change in the noise while turning. I also listened to the pump and its quiet. Since it makes the noise while the truck isnt moving, i have to rule out brakes and wheel bearings. IS there anything in the transfer case that spins or turns when the truck is in gear but not moving? Could the transmission pump make such a howling whine? But i have no funkiness coming from the tranny. Really it has not created a problem just a noise that sounds like something is about to seize up or let go. I have 186000 miles on the truck.

[o0firemaster0o]

Ok, I understand your post better now. It is something when you load the driveline...correct? To me I would think that nothing would be moving in the transfer case since your not moving. I would get a mechanics stethoscope and start probing the transmission while the vehicle is chocked and someone is holding the brake. Honestly I have never heard anything in the driveline sound like that. Thats why I suggested belt driven devices...ie alt, power steering. I dont think a tranny pump would make that sound, but then again I am by no means a tranny technician either. Hopefully some other mor knowledgable members will chim in.