Barracuda won't roll

Hi All
64 Barracuda. 71/4 ring gear,
I put the car on jackstands to change the pinion seal. Got the seal out but now I need to move the car before I can reassemble everything. When i put the car on the ground it wont roll forward, only backward. When I turn one of the rear wheels while on the stands, the opposite wheel turns in reverse.
The drivehaft and pinion yoke are still off. I'm learning as I go....what is happening in the rear axle that I can't roll forward?
Thanks in advance