Just had the rear jacked up checking the brakes.... Should the rear wheels be able to spin when the van is in park????

Not with a locker, and not with an AWD. The locker may allow the rears to spin slowly before locking (gov-lock) but the transfer case may be parked in either open or coupled mode.

Just had the rear jacked up checking the brakes.... Should the rear wheels be able to spin when the van is in park????[/quote]

Do you mean when you turn them by hand? Yes they can turn. Do you mean with the engine running? They shouldn't have power to them...