I have just had 3 cables of #4 aluminum wire run from my main panel to a new sub panel in my shed. I have them wired as 2 hot, 1 neutral. Maybe I should have run a fourth wire for ground, but too late for that since its buried 2 feet down.

With three wires coming from my main to my shed, do I need to bond the neutral and equipment ground in the sub panel box? I installed an equipment ground connector in the box and a grounding rod and I know that generally the neutral and equipment ground are isolated in a sub panel, but what about when only three wires (2 hot, 1 neu) are coming from the main?

I can live with 120v in the shed if I have to, so I can redo the main to send 1 hot, 1 neutral, 1 ground to the subpanel with my three wires. In that case, I assume I definitely do NOT want the neutral and ground bonded at the subpanel, right?

I am not turning on any power until I'm sure I have it right.

This will be disallowed in the new code, but now you need to bond the neutral to the ground, and use the rod as you mentioned. This will give you 120/240 volts.

Check with local code to see if another rod is needed.