4.8l 258,000 miles Silverado 1500 4x4. Here's the issue.Sometimes at warm start up,voltage drops to like 10,runs rough then goes back up to normal.Also,when coming to a stop,voltage drops,tach drops to @ 300,then climbs back to normal.Also notice pushing the brake fluctuates voltage and at stop,if I release brakes voltage jumps back up.Turn signals also bounce voltage.Any ideas where to start by in the know people? Thanks in advance.

 

Start by checking all your cables to and from the battery and alternator. Check the battery cables at both ends. Sounds like a loose or corroded cable. If this doesn't help then have the alternator checked.