Am I the only one who's not getting any sound on the videos? If the battery voltage is only dropping 1/2 volt while the engine is cranking, there's either a VERY bad ground path or the starter actually has an internal circuit problem that's keeping it from putting much load on the battery. One more test- - - - -connect the voltmeter from the starter housing to the battery negative post or at least the negative cable clamp, assuming you've thoroughly cleaned that connection already. You'll probably need to extend one of the voltmeter leads with a jumper to do this. Crank the engine. With the starter turning, the voltmeter should read less than 1/2 volt- - - - -the lower the better. If the ground path is good, swap starters.
Jerry
