For no reason at all my front dif.lock locks not in 4 wheel drive maken it VERY hard to steer 9mph and under, anything over that speed its fine.It doesn't do it all the time i did buy it used any ideas on the fix please post

Is the cable binding & getting pulled on when you turn the handle bars?

That system is pretty straight forward. Not to many probable failures.

Can also change the front diff. oil & check the condition of the fluid.