Just because the brakes aren't hooked up doesn't mean they aren't locked up.
As 565bbchevy mentioned, take one part off at a time and re-check. My money is on a brake catching the side of a drum or similar with a rotor. I'm guessing that when it was spinning freely on the ground you didn't have any rims/wheels bolted on.
If I'm wrong, then I'll buy you a cold one 🙂
Well 64nailhead, looks like I'll be the one buying the cold one.
I finally got a chance to pull it apart today. Pulled the wheels off and low and behold, the disk brake caliper was rubbing on the inside of the wheel.
I obviously didn't check it as thoroughly as I should have. It was just almost impossible to spot on the ground.
Sorry I even posted this post. I should have done a little more investigation. I guess my mind just jumps to complicated conclusions when something unexpected happens.
I appreciate all the help guys. Thanks for putting up with a new member/ self proclaimed idiot lol.