I saw a post on another RV Forum for a device from Hitch Rider.  The post claimed the Hitch Vise stopped hitch rattle for good.

I had been trying to solve the rattle my mobility scooter lift makes.  I had tried wedging wood, metal washers, a U-bolt device but nothing would stop the rattle.  This did :       http://www.hitchrider.com/nowobble.htm

I have no financial interest in this company or product just passing on a review of a product that really works as advertised.

I can't believe how quiet the SUV with the lift is when driving down the road after installing the Hitch Vise.