Intermittent electrical problem?
 

My truck is a 2008 Chev Silverado LTZ Crew Cab 5.3L. Truck hesitated a few times when starting, clock would reset back to 12:00. Service manager checked battery and said battery was no good. Replaced battery and it is still doing the same thing. Service manager at this Chev dealership is not that smart. Any ideas on what could be happening. I would like to give him somewhere to start checking.

Check the battery cables at both ends for corrosion and loose or bad connections.

they tested the battery and it failed. they didn't just drop it in for no reason. they found an obviously failed part and replaced it.

any starting, charging and electrical problem like you mention; must rule out a bad battery first. a bad battery will effect other testing.

the shop just stopped at the first problem they found. if the problem didn't re-occur for the techs after the new battery was installed after several start trials, they have no reason to continue further diagnostics.

what other devices are losing power besides the radio?
What does hesitating when starting mean? describe what's happening.