I bought a 2007 Sportsman 800 a month ago with a broken cage in the front differential. I pulled out the differential and replaced the cage with a new Polaris part. I filled the differential with Polaris fluid, but it's not operating right. Both front wheels kick in perfectly in AWD. When I let off the gas with the switch in AWD, the handlebars jerk to the left like the left front wheel is engaging. Any ideas what the problem would be? Thanks.