yet another starter problem

[Coleman]

So, I've all the sudden started getting skips or zings from my starter during startup. I replaced the clutch, flywheel last month and everything was fine. Last week I started getting chirps, squeals, screams from my starter and then it would catch and the motor would start. I took my starter in to be checked and it passed but it looked kind of worn so I opted for a new one. I hook up the new starter and it does the same thing, ching, ching, screech, screech and it finally catches and the motor starts. The battery is showing 12.5 volts and is fairly fresh, I have not checked the alternator. Is it possible that my flywheel has somehow gotten loose or I have some mechanical issue or am I having some type of electrical problem where the starter isn't getting enough juice to engage.

Truck is a 68 K20, 327, manual SM464 with a rockwell 221T.