Hello, I have searched the forums but haven't been able to find a solution so far. Your help is greatly appreciated.

1. My truck just recently started shuddering badly at around 15 mph. It vibrates at all speeds but is especially bad at 15 mph when downshifting into 2nd gear. The vibration occurs if the truck is in neutral, but is significantly worse when under load.

2. A whining sound seems to be coming from somewhere under the hood. It sounds like a pump that is running dry (similar sound to noisy power steering pump). I don't believe it's the PS pump but I can't quite locate it. It is especially loud in neutral at a stand still. Engaging the clutch will make it go away; steering doesn't seem to have any effect. I can feel a slight vibration caused by the whine through the shift lever.

I suspected a bad U-joint or bearing. I have just replaced both CV joints, the center support bearing, and U-joint at the rear diff (these parts did require replacing). None of this has fixed either problem. My local shop took a look and they say everything looks fine. I suspect the two problems are related as they started to occur at EXACTLY the same moment. I am out of ideas at this point. I was thinking maybe input shaft bearing or something but I'm really not sure.

Any help you can offer is greatly appreciated.
Thank you
Duncan