Mopar 8.75 posi. wont work. Why are there 2 rows of spline?

Keep in mind I only backed it in and out of the driveway twice and revved it a couple times to confirm the driveshaft was spinning and hear the noise etc. I never drove it like this, just revving and slight movement forward and back. Do you really think my clutch is burned up? and how much is a new one?