Changed out my starter today(3 bolt starter L6 250ci - Weird noise once engine starts

[Yamariv]

I've been searching old threads but can't seem to find the exact problem I seem to be having.

The truck starts and engages perfectly but once the truck is running, theres a kind of squeal/metal clanging that goes on for a few seconds then stops. Sounds like it's coming from the starter but by the time I get over to that side to stick my ears near it, the noise stops.

I've started it about 6-8 times with the new starter and each time the noise doesn't happen for as long. I'm guessing I need to shim the starter out but how do you shim a 3 bolt bell housing style starter. I'm guessing the starter gear is in too deep and getting hung up before it finally gets sucked back in?

Anyone had this same problem, what did you do to fix it?