Actually the most likely suspect.........and people who know me know I don't like "throwing money" at a problem.................most likely is the starter itself.
This would be my first suspect also, since they act like that when they get older and the armature gets off center.
The OE starters weren't power houses in the first place and heat just makes it worse.
The mini would change all that since like mentioned they crank WAY faster and use less amps to do it.
I got mine off a Ram 1500 pickup with a 5.2 for $15 out of the wrecking yard four years ago and it still works just great on my mildish 5.9 Magnum.
