[flyingtim01]

Well, two things. I feel like the noise is more associated with speed than RPMs, and I feel like if it was the exhaust, I'd feel it change with a change in RPMs, which I'm not. But I agree, I know it's something that I have to do anyway (like changing the U joints and tranny and t-case oil) so I'm not losing anything by just doing it.

I thought about the PTO as well. I used the winch about month ago to pull some stumps, and it seems like the noise started at some point after that. The winch doesn't engage and disengage very well just by using the handle, I have to get under the front bumper and use my pry bar and liberal usage of penetrating oil to get the engagement collar to move. So while I usually keep it disengaged (in case someone were to kick the PTO into gear while doing 40) I had forgotten to crawl back under and disengage it, which I also did this weekend, and it didn't seem to make an difference. I did verify that the PTO driveshaft isn't moving at all while the truck is running, but I didn't check to make sure that the PTO itself wasn't partially in gear like you suggested. The PTO handle is pretty vague as to where neutral is, so that will be something I check tonight. It would make sense that hitting a bump at speed may jostle the linkage a bit, just enough to move the PTO enough into gear that there may be some gear to gear contact, which would explain why I seem to feel it most under my feet. Hmm. I'll have to check into that one. Thanks for the hint, Stocker!