help with a starter on a detroit diesel 60

Common problem- some penetrating oil, an airtool and a universal joint on a long socket extension is the solution. When the bolt finally unscrews, slip some rubber hose over the bolt head to unscrew it. Use the rubber hose again to get the threads started and to get it finger tight.

That bolt next to the block is the toughest one.

 

I could really use some help from someone plz, when I go turn turn my truck in it does not turn over just clicks in the cab, I cleaned all battery terminals and wires, I replaced selonoid at fire wall, took all cables off starter and cleaned, still just clicks, I have been starting my truck with a wrench at the selonoid on the fire wall can also start with wrench on selonoid on starter, I have also checked fuses, can someone tell me if this is because my starter is broken or is there a way I can test it without having to take it out of the truck, this is on a Detroit series 60.