GM Repair Problems? Ask GM Repair Expert Now.
These trucks are notorious for faulty lifter cassettes. The lifters (they open the valves with the help of push rods and the camshaft) get gummed up and then get stuck causing a misfire and engine chatter.
Do you know what trouble codes are stored in the system?
That's usually the first thing they change when the lifters start acting up. I think the best bet is to get it scanned for trouble codes (most parts stores will do it for free) and see what system is triggering the fault. It's likely we will see a misfire code on one of the rear cylinders- they are the most common to act up.
Please let me know if you need additional info.