front wheels always spin

I have a AWD model 20353 mower that I have had for about 10 years. I recently started having trouble with the drive on the front wheels. I have replaced the belt and the transmission assembly. After my repair, even with the front drive cable disconnected, both front wheels spin when the engine is running. Anyone out there have any ideas why this is happening. I am normally pretty good at mechanical problem solving but this one has me scratching my head. Thanks!!!