Annoying shaking/vibration problem...GRRRR!!!

[creepskill]

hello alll......i have a 2001 gmc sierra 2500 hd and im having a shaking/vibration problem...this started about a week or two ago and it seems to be coming from the rear... my back right tire is almost bald and i could suspect cupping/wear because my other rear tire was bald and cupped as well and did shake for a while before it blew out on the highway, but im just not sure on this!....it starts to shake around 40 mph and when on highway speeds it seemed to diminish but i has just recently gotten worse over the past few days, so i have avoided the high way...the steering wheel does not shake but just seems to be the truck...i am frustrated and annoyed with this problem and could you PLEASE give me some input as to what the problem could be!!!

 

[dei38bud]

Did you check out your U-Joints if they are ok check your tires for broken belts

 

[creepskill]

problem fixed! turns out it was the tire, it was badly worn and had cupping all over it...went to sullivan tire, got a new tire and PRESTO! problem solved!