If I'm on short term and wsib, what happens to my wsib claim when I go on long term disability

Have a look through your LTD policy. Most LTD policies contain a provision that gives the insurer the right to claim credit for any WSIB payments you receive. So if your LTD entitlement is 2K per month, and you get 1K per month from WSIB, then your insurer will only pay you 1K because of what you are already getting from WSIB.