2000 sierra Vibration

[Blacksierra]

Hey I ahva a 2000 sierra Z71 ext cab 5.3 4wd and I am having some bad vibration at hwy speeds. It is noticable at @60 and gets worse until 70 where it subsides slightly. After that it gets so bad that at 80+ I cannot drive it. I am the second owner of this truck and I bought it from a used dealer who put brand new tires on it and seems to have balanced it all correctly. I am pretty sure it is not a tire balance issue. 2 things I have noticed, one is that instead of an aluminum driveshaft I have steel piece and two, where the balance weight is on the driveshaft I see that there is a large hose clamp over the weight. I have heard this is a GM fix for the balance weight but I am not sure. Can anyone shed some light on what could be my issue and possible fixes?
Thanks

[PK55Z85]

a tire could be balanced..but still out of round
post the last 8 of your VIN...can check about the clamp issue

[GMCTech]

Have your driveshaft balanced by a driveshaft shop.

Hope this helps.

[fuzzypuppy]

I'd have to say tires as well, I have had tires that balanced right but when you looked at them spin on the balancer you can see the wobble, as well it seems that if it was the driveshaft that was out of balance bad enough to cause you not to be able to drive it a u-joint, carrier bearing or somthing would let go real quick.that part is just my opinion though. but if you want to check the shaft put the rear end securly on stands so the rears are off the ground have someone get it up to speed while you look under, if it is the driveshaft you'll see as well as hear it you can check the rear tires at the same time as well

[Blacksierra]

Thanks for the response. I'm going to throw the wheels on the balancer this week and check them. If that does'nt do it then I will check out the driveshaft. Who is qualified to do a balance job on a driveshaft? Is it something that a local shop could do? I'm in Connecticut, any place someone could reccommend?
Thanks

[PK55Z85]

make sure you find someone who has a machine that can check "radial force variation"...that is what checks the tire and rim for out of roundness.