I have a 04 2500hd ec sb 4x4 with 6.0 4l80 and recently at about 66 to 68 mph I can feel my truck shake, if you speed up or slow down it goes away, also if you stay at that speed and drop it into 3rd it goes away. Has anyone else experienced this problem?

I took it to the stealership and they of course said my tires needed balancing, so they charged me for that and as soon as I got it on the freeway no difference. Any help would be great...

Sounds like your U-joints in the drive shaft.

Tire balancing? U-joint vibe would be constant under acceleration normaly and disappear on deceleration.

Could u-joints go bad in 17000 miles?

I doubt it too; I changed my first one @ 152,000km and WAS not gentle for most of these KMs... Unless it was hit somehow or defective from the start.