2008 Subaru Outback won’t move!

[Rccrypto24]

I purchased a 2008 Subaru Outback that needed a clutch. While having the engine pulled and replacing clutch I had noticed that I could spin the shaft coming out of the front of transmission freely even in gear. I new this was not good yet still reinstalled motor and not to my surprise the car does not move. It goes into every gear and you can even hear the different speed noise pitch of each gear. I checked the front cv axles and they are intact and not broken. I jacked the rear of vehicle up as well and when not under a load and in gear the vehicles wheels turn.
What can cause this… bad front or rear differential?