Hey fellas. Help! Specifics.

04 sportsman 700 twin. Carbd. Purchased used. All was "good" when purchased and tested out AWD. Got it home, changed all fluids, looked good. Ran it, AWD light went out after testing it for a while, as did AWD. Pulled diff. Plastic cage was lightly busted. Swapped it with a super ATV Sprague. Still no AWD. So...here's how far I've diagnosed.

Everything is Working, speedo, gear selector, says I'm in AWD at speedo. Reverse, all Indictors on dash work and light up as they should.

Put 12v directly to differential and AWD locks up fine, as it should. Remove 12v and it releases as it should. Everything in diff looks good. Tested resistance. Good. I have 11.8v at the differential plug at pod. With switch on. Drops with switch off, as it should.

Could the speedo senor be bad even though it senses speed at the wheel fine? And shut my awd down? How to test?

Or what other wiring/sensors can I test.

I don't have a AWD light at the handlebar switch. I tried jumping the ground too. No change.

Words of wisdom is much appreciated. What next?