I have bought this 08 Silverado LTZ used with about 60k on it about a year ago. The first month after i bought it i had a knocking sound from the rear of the truck. I took it in to the dealership and they couldn't find anything wrong but the lubed all the joints and said it was good to go. Well I serviced the the truck regularly since then and haven't had a problem till the beginning of December. the noise came back and i cant seem to find it. Every time I stop at a light / stop sign then go i get this knock or clunk like the transmission isn't fully in gear or the rear drums aren't releasing. i tried hard stops and easy long stops and either it does it. Could it be differential, drive shaft, rear drums, or transmission? they all look good and don't seem to be worn abnormally.