8 3/4" 741 why this happen

That happens a lot to that cone-type SGs. It usually starts when the cones bottom out and you start doing one-wheel-peels. Yours is nearly the worst I've ever seen. I've had some of those repaired over the years, but I think yours is done. Once you get it apart, I think the guts will be done-for too.You're probably lucky, cuz they occasionally spit the pin out, before it gets that bad. Ima thinkin at least one spider is welded to it. Yup, one-wheel-peels will do that....
If you're running a BB, I think it would be time to upgrade.