The usual practice is hardened thick SAE washers, then tall nuts.
Occasionally with some blue thread locker, at least the u-bolts on a 2005 Freightliner suspension and rear axle I used on one of my trucks had loctite on them, and it was a new takeout, no miles.
I don't think I would use lock washers, as they can split and fall out, same reason you don't use them on rod bolts. Re tighten them after some driving a few times, then you should be good to go. Or get them really tight the first time with some thread locker.
I just tightened the ones on my 48 6400 a few days ago, I put neverseeze on them, as I will be taking them off in the future to add shock brackets, I don't expect them to loosen on their own though.
Grigg
