What would cause a model T / TT drivetrain to lock up?

So my Grandpa has a '26 Ford TT truck. He's been around it for years before he bought it and knows it was running/driving not long ago and is certain the engine and such is good.

Here's the thing though, the previous owner messed with something in the rear end (bearings, brakes) and insisted something needed adjusted in the transmission, and then did so.

As it sits, NOTHING will turn. Engine won't turn over, even in neutral the rear axle won't turn, etc. The entire thing from end to end is stuck. I guess the rear end will turn a little ways, then stop. Turn back the other way a little, then stop.

We're going to pick it up on Wednesday and I was going to mess with it and see if the engine will rock back and forth a bit at all. Though, even if that was seized, it seems like that it would still roll on all 4 wheels.

I'm guessing something was messed with in the transmission and causing it to be locked together.

Anyone here have any ideas on things I could check or adjust/loosen up on this thing? I've never messed with a T before, so I'm at a loss here other than I think the issue is in the transmission. I'd really like to get this thing to run and drive again. I've never driven one, so it'd be fun for me to take it for a ride.

 

Finding neutral is done by moving the parking brake handle, and all T's are unique, you have to find it by taking your time. Jack up the rear wheels, have someone try to turn them while you move the lever forward. Bob

 

Theres goofy adjustments.
My buddies was almost like you described.
I took the trans cover off to see what was happening and it took us about 45 mins to get it.

 

Looks like I'll spend my Thanksgiving laying under an 86 year old truck then!

I've been searching and researching, it looks like they mostly don't like sitting and don't like being messed with by someone who has no clue what they are adjusting...

Looking forward to messing with this thing. Hoping I can get it to run/drive on it's own. It's fun bringing things back from the dead Plus, I've never driven a T and really want to take this thing for a spin.

I guess the previous owner added what gramps called "mountain brakes" to it as well, brakes on the rear axle. They normally only had the internal brake on the transmission, right?

 

TT worm drive If the drive shaft mounts to the top of the rear end housing then It has a worm drive and it is next to impossible to turn the wheels, It is a one way process the drive shaft has to turn the wheels. Pull the top cover on the trans and check out the band adjustment, moving the left pedal , all the way to the floor tightens the low band , when the pedal is half way down the band should let the trans turn, all theback the internal spring applies the high gear clutch. the E brake hahdle has that small cam that moves the hi-lo pedal mis adjustment of the long contact bolt can have the rear brakes on.