Diagnosing the Screech on a Silverado LB7 Diesel Engine


It was back to work for us, since the new alternator and belt arrived. We installed the alternator, and skeptically fired the engine. 

Sure enough, another new pitch was revealed. This new pitch was at least less frightening than the old, terrifying screeches. We removed the belt once again and briefly fired the engine to test the crank. Fortunately, there was not a noise- indicating that the crank was indeed in proper working form. This also revealed that our old belt, which was less than a year old like the alternator, was another source of the infamous screech. Fortunately, we purchased one from the parts store, and Rob quickly installed the new belt. 


We fired the engine one last time, and it was as quiet as a mouse! Well, it was as quiet as a 403 cubic inch 6.6L V8 diesel engine could be. 

In our case, the “infamous” screech issue found in this generation of SUVs and trucks was due to several issues: a resisted idler pulley and a less-than-perfect alternator and accessory drive belt. We are grateful that there weren't any issues with the crankshaft, although we did not anticipate this to be the issue. With all squeaks and screeches sorted, the Karla Pestotnik Racing tow rig is ready to roll to the Global Time Attack/Honeywell Garrett Boost Fest event. Stay tuned for our coverage of the event!

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