Thanks for all the suggestions. Yes, I've replaced the entire assembly, bushings and all.
As to where the bolt fails, I'm double nutting it on either side of the outside shackle plate. Looks like the bolt failure is on the inside of the inside nut, if that makes any sense.
The bolts are 3/8" x 3 1/2" coarse thread. I will try some of your suggestions. Seems to me that the only reason a carriage bolt was used is that the shackle plates have square holes in them that (I suppose) keep the bolt from turning at all.
David
Last edited by David Bush; 11/02/2014 2:22 PM.
