So I have a quick question, what are signs that U-Joints are going bad when driving?

 

Clunking when shifting into drive or reverse from park, clunking when re-accelerating after letting off gas, the drive line vibrating at any speed are the more common ones....
if at any time your drive shaft falls and plows a furrow down the street, its a good sign the u-joints have failed....

 

Ok thanks...the reason I ask, I have an 08 Tahoe LTZ with 65K miles on it, just bought it in Jan. The more I drive it, i've put on 4K since I bought it. When I accelerate especially if I step on it harder, there is a lot of vibration during acceleration which I didn't notice much when I first got it. I don't get the clunking noises when shifting, it's just the vibration. Does this sound like this could be the issue and the clunking is yet to come?

 

Without being there and feeling what you are feeling its hard to say....
You can get under the vehicle and try twisting the drive shaft to see if it has any play in it... but your vibration could be coming from any number of other things...
I'd check them for snug-ness and for any signs of degradation, yours are still "pretty" new to be out just yet....

 

that's what I would have thought, My dad has the same vehicle just different color with 120K and doesn't experience any of this. Its just strange. What's even stranger is, a month or so back when I drove it in Auto 4WD due to weather, the vibration seemed to get better. Then when I switched it back to 2wd the next day, it was better, then started to get worse again after a few days of driving. Doesn't make any sense, atleast to me.

 

Check for any obvious things like something wrapped around the drive shaft...
try rotating your tires to see if it moves with the tires
Check your wheel hubs aka wheel bearings

 

All the tires have been recently rotated and road force balanced, nothing changed it. Another thing I just remembered when you get up to 70mph to 75mph, all vibrations go away.

 

My rear shaft u joints failed at 108k on my 08 sub.

 

So took mine in today...rear u-joint shot...it started squeaking on friday when driving.

 

Thanks for following up with the findings