Replaced worm gear but slips with any resistance

Hi, I replaced the worm gear on my Kitchenaid Artisan mixer. It spins but when it encounters any resistance it slips and stops. Any ideas why?

crwdns2893858:0crwdne2893858:0 crwdns2893862:0crwdne2893862:0

crwdns2894050:0crwdne2894050:0

crwdns2889612:0crwdne2889612:0 0
crwdns2892346:0crwdne2892346:0