Short version....starts at post 354 of the Official John Lee Jr Thread for the complete story.....
Next to removing the single pot master and splitting front brakes from rear then adding a dual pot master, I think one of the best and likely cheapest ($30 or under) safety upgrades you can make on these old trucks is to replace the 7/16" lower control arm u-bolts with the more modern and less prone to breakage 9/16" u-bolts. If everything goes well, its about a 3 hour or less job and you won't loose the lower half of the suspension when one of them old and just a whisker larger than muffler clamp u-bolts lets go. Typically, on these old trucks the stock 7/16" bolts break when turning, especially backing up. Over the years GM upgraded to 1/2" u-bolts, which also break. Then finally to 9/16". Haven't heard of these breaking. They are a close fit, very close but follow along and we'll get em in and just enough room for a socket on the big prevailing torque nuts at the front inners with a bit of dimpling of the cross member.
If your rebuilding the front end, pefect time to do this mod when the lowers are off. If you just want piece of mind and safety, jack stands and jacks and don't get under the control arm any longer than you have to, always do one at a time so you at least have some extra margin of safety. i.e. I only removed one shackle at a time...installed the new one, torqued it and then removed the second shackle....!!!
On Ol John Lee, the 64 C10 I used the LMC u-bolts. At $15 each and w/o prevailing torque nuts, they were highly expensive but worked just fine. If there is an advange to the LMC u-bolts, its that they have taller nuts allowing standard sockets to be used. I almost had to go to a deep well socket to get these Dormans in place. By the way, these are available from Oreillys and Auto Zone for $8.99 a pair. Considering there was no shipping, about 1/3 the cost of four bolts from LMC. And, I like the prevailing torque nuts better, no lock washers required.
The old and the new side by side. A huge difference in brute strength. I'll be more comfortable with my lowers riding in these new beefy u-bolts. Got a lotta miles to cover starting in Sept, its hunting season all over again!
These dorman u-bolts are a bit finer finished than the LMCs. The LMCs are not coated with a gold rust proofing. In addition, the LMCs were too "open", I had to install nuts and smack em with a large SmasherWacker to close em up to go into the holes. These Dormans are just fine, drill the holes to 9/16 and tap them right on into place. Here I'm drawing up the prevailing torque nuts evenly, alternating back and forth until its time to put on the torque wrench and finish them up at about 80 foot pounds. (My spec, the 7/16 factory nuts backed off easy with 8" long 3/8 drive wrench!
Just to be sure, I compared the old and the new for thread depth....there is sufficient extra thread on the Dorman replacments that I will not need spacers or washers under the prevailing torque nuts...just run em on and torque em down.
