Noise Front Rear! (I think??)

[ACerf]

I have been experiencing a noise when my truck shifts into lock-up in OD. It is hard to discribe the sound but it does not sound like a metal-to-metal sound. It is more like bump sound, if that makes any sense! I had a dealer take a look at it and he thought it was the U-joint at the rear. They removed the drive shifts and found nothing wrong. Checked for loose engine and transmission mounts... nothing. I noticed that it likes to do it more when it is wet and the chassis has water on it... like when it rains. Have no idea if that has something to do with it or not. I can drive the truck for days with no noise and than other days it might do it twice... sometime, very loud, that is usually when I am towing my fiver. At first I thought is was because of the trailer, but it did it even without it. While visiting my daughter in Phoenix I took it to another Dodge dealer to see if they could find anything. It never even made the sound... of course vehicles never act up when they are at the dealer! Anyone have any ideas as to what this sound might be?? :{

 

[rbattelle]

Could it be axle hop? Does it tend to happen mostly when you're giving it a lot of throttle?