Like I was saying.. in traffic, at slow speeds, if I let off the gas completely and then when I give gas again to continue accelerating, it's not smooth... kinda jerks. Don't feel like the transmission at all. Could it be drive shaft or U-joints? there is also a slight vibration at highway speeds (not the steering wheel) coming form under the truck.

Any ideas where to start looking?

 

No noises at all... which would be a better indication to bad u joints... but all is quiet... for now

 

My truck does this too, 08 Alpha.

 

reach under and rock, push/pull the driveshafts. see if any loosness. it should show if u joints

 

Happens to me also. Almost like a lag or space between the gears in the transmission. Just replaced my trans filter, but no particulate.

 

Every rear wheel drive (4x4s also) GM vehicle I have owned in the past 15 years has done this. At first I took them to the dealer and they said "it's normal". Now, I don't really notice it .... until you brought it up.

 

Check your front diff crossmember. Mine went and it felt like a u-joint. It seems to be kinda common if you wheel the truck. Its easy to see if you remove the skids. Lots of threads on fixing it, if thats your problem. Good luck