vibration in 2001 4.4

I test drove a used 2001 4.4 with 35k miles and sensed a vibration/hum at about 5000 rpm when the engine was under heavy load (like hill climb). It seemed to come on suddenly and go away just as quickly as it passed 5000 rpm. My question is - could this be something that is typical of this year/engine or might this particular problem. Any notions what that problem might be?
thanks for any ideas.

I test drove a used 2001 4.4 with 35k miles and sensed a vibration/hum at about 5000 rpm when the engine was under heavy load (like hill climb). It seemed to come on suddenly and go away just as quickly as it passed 5000 rpm. My question is - could this be something that is typical of this year/engine or might this particular problem. Any notions what that problem might be?
thanks for any ideas.

How intense was the vibration/hum. If it did not seem that bad, then I would say it was normal however my 2004 4.4 does not do this, but it is a slightly different engine than the 2001.

How intense was the vibration/hum. If it did not seem that bad, then I would say it was normal however my 2004 4.4 does not do this, but it is a slightly different engine than the 2001.
Thanks Joe. I walked away from this car, not knowing what was causing the vibration. It wasn't an intense vibration but certainly noticeable when you hit the "sweet spot". I've since purchased another 2001 4.4 at a local dealer. No vibration in this one so pretty sure something was funky with the first one.
thanks for the help. have a great T-day!
phil