Or remove the receiver, drill a 3/8" hole in the top one inch in from the furthest point of the hitch. Weld a 3/8X24 nut over the hole and then all you have to do is tighten the bolt down onto the hitch. This will keep it from tipping up and down. Also check to see how much slop is in the pin hole on both the hitch and the receiver. If there is too much you can drill out the hitch and sleeve it for a loose slip fit on the pin (measure the pin and add +.005 to the diameter). For the receiver you can weld a thick washer to it over the existing hole.
Don