(pics) '66 lower control arm u-bolt broke today, luckily in my driveway
 

Just pulled my truck out of the garage and parked it to the side when I came to a stop I heard/felt a loud pop. Jumped out to discover this... https://static.wixstatic.com/media/1...a4fcb~mv2.jpeg

Funny thing is... it's scheduled to go into the shop in a couple months for a complete disc brake and 5-lug conversion and 2" lowering. Not sure if there were signs that this u-bolt was about to fail or not. Just sure happy it happened at walking speeds instead of highway speeds!

I found replacements at Classic Industries:https://www.classicindustries.com/pr...lcuk63725.html
I'm surprised they offer them in 7/16" or 1/2", not sure why someone would choose the smaller diameter, any ideas?
Any advice before I go outside and start getting my hands dirty on this repair?
https://static.wixstatic.com/media/1...64aa4~mv2.jpeg

Re: (pics) '66 lower control arm u-bolt broke today, luckily in my driveway
 

That's a relatively easy fix. If you can't get the two pieces of u bolt out because of the bend don't waste time trying to get the nut off, just zip it off with a cutoff wheel but do 1 at a time with a jack supporting the arm. If you remove both the coil spring will make things difficult. As for the choice of 7/16" or 1/2" I can only guess stock is 7/16 and if you want to drill a bit you can upgrade to 1/2. I'd say most people would do the pivot bushings now but that can wait till everything is off getting upgraded

Re: (pics) '66 lower control arm u-bolt broke today, luckily in my driveway
 

Had the same thing happen to my '68 3/4 ton. I was loaded down with camping gear and pulling my 13' camper and hit a pothole. Almost hit a pole when the control arm moved back. I went with the larger U-bolts. Glad you were just moving the truck at low speed! Beautiful truck by the way.

Re: (pics) '66 lower control arm u-bolt broke today, luckily in my driveway
 

I didn't have one break, but I did replace and upgrade mine to the 9/16" bolts used on the squarebody trucks. Yeah you have to drill the holes bigger, but if GM went bigger with the U bolts, I don't mind drilling some holes to do the same.

Dorman 13503 is what I used to replace the originals on my 63

Re: (pics) '66 lower control arm u-bolt broke today, luckily in my driveway
 

Don't use a drill, the center to center length isn't the same. The holes need to be enlarged outward in width and forward away from the upper crossmember wall for more clearance for the nuts. I used a carbide burr in an air grinder to open mine up wider and more forward.

Re: (pics) '66 lower control arm u-bolt broke today, luckily in my driveway
 

I did the exact same and the peace of mind is worth the upgrade!

Re: (pics) '66 lower control arm u-bolt broke today, luckily in my driveway
 

Do the holes need to be moved outwards for both the 1/2 and 9/16 bolts or just the 9/16?

Re: (pics) '66 lower control arm u-bolt broke today, luckily in my driveway
 

Great input everyone, thank you.
I'm trying to enlarge the pair of holes for one ubolt before I disconnect the other ubolt to keep the coil spring in place, but this doesn't give me enough clearance to get my carbide burr in there. Any suggestions?
I have a lift I can use to get the truck overhead, but this presents the problem of needing a 5' tall jack to support the assembly whilst working on it.
Too heavy to just have a buddy hold it whilst I grind out the holes.

Re: (pics) '66 lower control arm u-bolt broke today, luckily in my driveway
 

I'm also concerned with the possible need for a washer if we're making the hole oblong. It's pretty tight where the nut must fit, not sure if there's even room for a washer.