Engine ticking on startup, lasts for 5 minutes currently - longer on cold starts or after letting the car sit overnight. Progressively has gotten louder and longer in duration since reporting the failure last year to the dealership. This piston "slap" noise described appears to be manufacturer defect in 5.3 liter engine where shipment of engines with cylinder heads that are oversized or pistons shipping as undersized is causing warping on piston head, hence the reason why the noise progressivly gets louder and longer lasting as time progresses. Original dealership has documented the report of the noise with no result or attempt to fix. Customer has purchased extended warranty prior to the evidence of this failure, at time of purchase. Several dealerships have directed customer to file a direct complaint with manufacturer as engine has been diagnosed that prolonged wear with the "slap" that is causing the ticking noise will cause serious damage to engine over time. Only suggested recourse is to replace engine with 5.3 that shipped after September 2002 and was not manufactured from one of three GM plants responsible for the manufacture of the defective engines.

- Salt Lake City, UT, USA

The consumer indicated that GMC manufactured a large number of 5.3 liter engines with either under sized pistons or over sized combustion cylinders which resulted in piston slap. The noise is very loud when the engine is cold but after a period of 10-15 minutes the noise goes away. The consumer indicated that the manufacturer would issue an extended warranty to consumer's who contacted them about this problem. The consumer feels the manufacturer should either replace the engine or repair the problem.

- Waterloo, IA, USA

While driving 40 mph vehicle stalled and lost power.

- Oxnard, CA, USA

Engine shut down at 65 mph on expressway lose of steering, difficulty with brakes was nearly in an accident trying to get to side of expressway.

- Livonia, MI, USA

While driving at California freeway at 55mph and with no warning vehicle shut off, causing consumer to pull off the road.

- Oxnard, CA, USA