I have a 02 suburban. After driving for about an hour, there is a vibration that is not related to engine speed, but is related to wheel speed. It'* pronounced at high way speed. It'* similar to a rumble strip. It'* not a bearing, as it'* the same turning either way. Rotated tires, no change. I'm thinking u joint, front diff, or transfer case. Just had the trans pan off, pretty clean. Thoughts? Thanks!

Rumble strips........u joints.

Thanks for the very late reply. I shall give it a go!!

So the front prop shaft is turning in 2wd, but I am trying to determine if the front diff is engaged. Maybe a bad switch? No idea when the trans case was serviced. 119k miles.

The front diff appears to be disengaged in 2WD and responds to the switch commands. I am wondering if the transfer case has an electrical issue, plus the u joints.

Even with the front diff disengaged......driving around in 2x4.....the front axles are still spinning. Here'* a link to something you might find of interest: Front Differential Noise - 1999-2006 & 2007-2013 Chevrolet Silverado & GMC Sierra 1500 - GM-Trucks.com

....specifically the info relating to the axle carrier bearings inside the front diff.

It looks like there is a leak on the drivers side output shaft. Maybe the bearing is shot. Looks like I need to get it down and opened up. Might takes be a while.... Thanks