More connected with MPH than RPM, right? (i.e. not parked and revving the engine).
So, it's something mechanical (likelihood) such as CV joints, U-Joint, bearings, brakes, differential, transfer case.. perhaps motor mount.
Any shop would examine the physically accessible parts (e.g. u-joints, CV, bearings while on a lift) and take it for a test drive.
Most good mechanics will be able to hear and home in on things advanced enough to be failing and generating noise. They've got some good tools for that too.
Occasionally - these things are subtle but in this case it's not really a 'diesel' thing as all the parts I've listed are common to the 3.7L gas engines. I don't think the engine noise will mask it too much.
You might pop the hood and watch the belt around the alternator and particularly the tensioner (bottom left while facing the grille). If the clutch on your alternator pulley is failing you'll see a bouncing and jerking, hear a rattle and possibly some belt squeal, and start to experience tensioner/idler/belt failures.
Mark
tedder wrote:
I'm hearing noise from the front and can't tell if it is the engine (normal eng sound) or the drive train. The noise is continous at 55 and gets quieter as I speed up. Its' not loud at all at 45. It seems to be RPM connected. It also gets louder when you let off the peddle. I'm use to my cummins sound so I'm not sure what these 4L's should sound like much less with an automatic. I saw some other posts that were talking about a HUMM and the front differental bearings but not sure if that was the same as what I'm hearing. If I was to take it to a shop could they diagnose it or is the diesel thing going to most likely confuse them?
Thanks