power drain when attempting to start

Yall have always been kind and patient. i finally have time again to work on my truck to fix my exhust leaks and am having issues starting again. Previously i thought it as simply a matter of moisture and dirt; cleaning and reattaching the starter solenoid wires seemed to work before. Now it seems to be something else entirely. If i could have even some clues about which direction to troubleshoot please.

Battery is good and charged. Connections on battery are good and cleaned. Power seems to be fine for lights etc. When attempting to start with key, there is a click (maybe more like a hum or an ever so slight grind) but absolutely no attempting to start. This is coupled with extreme power drain enough that cab lights go out completely. i turn off key and have not left it long enough to see if lights come back, i pull the battery cable because i am worried about damage.

Jumping past the solenoid (used jumper cables to connect neg to truck body and positive to starter cable on the solenoid.) causes the same problem just without the key; sound of the starter charging but not cranking, power drain.

My best guess is some kind of bad ground connection? i feel dumb...

I was going to say ... check your fusible links... but if you have trouble cranking... its probably a ground issue. Check your battery to frame ground connection, near the passenger side exhaust manifold.

Could be a bad fusible link if you have little to no power in the cab. Probably link J at the starter solenoid.

When my fusible link went bad once, I could not crank, had no power in cab... but in your case you seem to have some.. So wondering if the fusible link is barely hanging in there.

Definitely check the ground cable to the right corner of the block, and check for corrosion where the 'flag' attaches at the frame crossmember.

If a simple clean and tighten doesn't fix your starter problem I would say, -if you have one- use a clamp-on ammeter to see how much current the starter is taking, or just take it off and bring it to the parts store for testing.

Try the jumper cables again but with the ground connected to either the engine or better yet right on the starter. A bad starter could be causing this issue as well as a bad connections. I'm assuming the engine turns freely.

I've seen batteries with good voltage but have internal issues and couldn't supply the amperage.  

Absolutely true.

That's why it's best to test a battery with a load tester and not a voltmeter.

I'm thinking starter, but I have no idea of the battery condition.