Slick 60's

My truck is From Georgia, and some of the undercarriage bolts have an extreme build up of dirt/clay especially the leaf springs u-bolts. Any one have a similar issue or know of a solution. I soaked them in a mixture of brake cleaner, degreaser, and gas, then scrubbed with wire brush and still can't thread a bolt all the way to top of threads even with a breaker bar on my ratchet.

use a thread die or chaser?

Brass wire wheel on a drill

BigMike wrote:Brass wire wheel on a drill

Fine wire one.
After you get it pretty clean try some rust remover like Blue Lightning (acid type not the ones that leave the black coating and the scale underneath).
GM sells a penetrating oil/rust acid combination in an aerosol can that seems to work pretty well too.

Lowell wrote:use a thread die or chaser?

I`d have to agree with Lowell!, but would put new ones in myself!

Southern64,
Before you get too mad at those threads, just be thankful you even HAVE threads!

If your truck had been from Midwest where they salt the roads every winter, the threads would be gone, the nuts would seem welded on! With a rust-belt truck you have to approach any under carriage work with the pre-understood acceptance that any and all fasteners/bolts/nuts will simply need to be cut off (sawzall, hacksaw, torches, cutoff wheel), (which is easier than twisting them off), and simply plan on new bolts & nuts to be installed. New bolts are cheaper than breaking a socket or stripping out a ratchet.
If for some reason you feel you must try to salvage the bolts/nuts, use a lifetime replacement guaranteed socket (that you have two of) and a breaker bar with a cheater pipe extension (don't use your ratchet, you can break that too) in which case you can get it replaced if you break one or both. Yep, I've broken sockets and ratchets during such tasks along my learning curve.

Ok, back to your question: Yep, submerge the U-bolts in fuel oil to soften the rust overnight, then let them drip dry for 10 minutes, then I'd go with a wire wheel on a bench grinder. Finally, place them in a bench vise and run a thread die down each leg. I'd say that is as good as it'll get! Realize, that if the threads are 50% gone, their "holding power" to stay tight is also lessened considerably. If it's just a muffler clamp it's one thing, but U-bolts that hold the leaf springs tight should not be compromised. Also realize that if you're using the OEM spring pack, you will not need to be able to thread the nut to the top of the threads, since the nut won't need to go down/up that far.

Keep us posted on how well you progress!
BarnieTrk

Thanks for the advice guys! It's funny this is actually for my front leaf U-bolts. I only had to cut one taking them off, and at that point had new ones made from a machine shop. Now a few years later I lowered the front temporarily by removing leafs. The ones I got new are too long and not threaded enough, so that is the reason I need to thread all the way up on the stock ones now. Until I give in and buy Monos....

how much further do they have to go before they are tight ?
some good quality thick washers might be enough of a 'spacer' if not too much
i rarely re-use ubolts... but if yours arent that old , i guess its ok.

Another thought would be to replace the springs you took off the bottom, and replace them on top as spacers... depending on how many you removed.
I did that with the overloads on the rears, as a temporary stop gap until I am sure that the mods are what I really want/ need.
John

When the bolt starts turning hard, tighten it back up some and spray it with some more PB blaster and use a wire brush if necessary. Keep working it back and forth and it will come off, just have patience.

I vote for new ones...keep the old ones for "spares".