2001 P38 4.6 HSE 125,000 miles

I have a loud growl/whine coming from the front of my truck that increases under acceleration but is alson noticable at low speeds as the truck is slwoing and downshifting. It alsmost sounds like dry metal rubbing against dry metal.

I have checked the transmission fluid. It was full but I drained it, replaced the trasmission filter and refilled. The ols fluid was a bit dirty but had nothing metallic in it.

Next I checked the differential fluid and it also loked fine but I replaced it as well. I did the same with the trasfer case and there was no apparent problem wit the fluid in the transfer case either.

I had replaced the front U-joint on the rear drive shaft a month ago but the rear U-joint seemed fine.

The transmission shifts fine, there is a slight shudder at around 30mph but other than that there does not seem to be any performance issues with the drivetrian. The noise will stop and medium speed with my foot off the accelerator so it doesn't appear to be a wheel problem.

Obviously the noise is an indication that something is not right and I would rather fix it now than have a bigger problem later. I'm at a loss as to how to diagnose the issue. Could it be a bearing or spline problem with the differential or transfer case?

If anyone has any ideas, I would certainly appreciate hearing them.

Thanks

Mike