Check your U-bolts!!

[Mastiff]

Went for a casual trip up into the mountains right near home. It's rocky dirt trail and I did just a bit of mild wheeling to check out my new components (recent additions include new 1-tons, ORD springs, Bilsteinens, crossover). All seemed well, but after the wheeling part it seemed like I was having to steer to the right a bit to go straight. I couldn't really tell for sure because of the side hills and stuff though.

So I went over a rough, rocky section and heard the sound of a piece of metal flying off the truck onto the side of the road, then a bunch of ugly noise and I knew something was seriously wrong.

I was staring at it and it took a while to sink in what had happened. The u-bolts had loosened up from all the rattling around, and somehow I lost my center pins and DIY4x shims. The piece of metal that flew out was the bottom spring from the pack. The axle shifted back (not sure if the shock or the body stopped it) and the driveshaft fell out.

Some guys stopped to help but we couldn't figure a fix to get me home on my own power. The biggest problem was lack of a replacement center pin, and my failure to pack a deep socket for the U-bolts. I may have been able to limp home if we had two tall high lifts and a good ratchet strap. Thankfully I was close enough to town to call for a tow. The guy used his wrecker bed to lift the back of the truck and we ratcheted the axle forward to get it on the truck.

I have not full assessed the damage yet. At the least I need new U-bolts and shims. Hopefully, all the leaves can be accounted for. I'm not sure about the friction pads between the leaves.

In the end I'm not sure what I did wrong. I torqued the U-bolts multiple times. These are the ORD ones that come with tall nuts, that don't have nylock inserts and aren't oval to stay cranked. But that must be okay since half the people on here use ORD stuff, right?

 

[K85 Octane]

Wow, but there's a thread like this every 5 months or so, so don't beat yourself up too much.

The U-bolts and nuts are fine. There is so much torque on the nuts that they aren't going to rotate loose. Also, a pinch nut doesn't play nice with fine thread shanks, most pinch nuts are on coarse threads. The nylocks are nice, but most of the nuts I've used that are of this size seems to destroy the nylon inside while tightening. Doubling the nuts might help, but they don't loosen over time because they back off. They loosen because the U-bolt stretches and allows slop, giving the impression that the nuts loosened.

Really, I've never seen BOTH center pins break before, at least not without a major accident being the cause. Did you have the axle moved back with the blocks? Even if the U-bolts came loose, the pack should have stayed together with the blocks. Mine is moved the 1.5" and has been on the same spring pack and pins for over 3,000 miles.

 

[Mastiff]

The only slightly unusual thing I have going on is/was some thick shims (maybe 8*, I'll have to look it up in my email). They were good DIY4x ones though, with the flat spot for the center pin so it stays parallel. The head of the center pin is at an angle to the spring perch though. But I doubt that was a contributing factor.

I still can't quite imagine how the center pin broke and managed to completely disappear. And on both sides. I guess the U-bolts loosened and all the load was then on the pin. The head broke off, then just from rattling around it somehow went up and out. With one side flopping around, it surely sped up the demise of the other side.

 

[Deuling]

Thats crazy. I just reefed down on my u bolts. Havn't had them stretch at all yet....

Did you just torque them once? or multiple times after a quick run?

 

[Hogback Fabrication]

The center pins are tiny and will break as soon as the u-bolts get halfway loose, all they do is hold the spring pack together and help line up the axle for install.

Your u-bolts got loose, one way or another. It happens with leaf springs, they need to be checked pretty much every trip.

 

[Mastiff]

Did you just torque them once? or multiple times after a quick run?

I torqued them, then did it again after a few short trips. I've hardly been driving it though, so they went from tight to loose in under 50 miles.

 

[rampage]

Your u-bolts got loose, one way or another. It happens with leaf springs, they need to be checked pretty much every trip.

Why isn't this a problem with new vehicles? When my dad bought his 89 Blazer the dealer never said 'And by the way, after the first 100 miles and after every off-road excursion, you need to come see us so we can check to see if your u-bolts are still tight'.
Are the factory u-bolts different from the aftermarket?

 

[K85 Octane]

Does your build thread have any shots of you putting things together? Maybe see a problem in a previous post? Dunno

 

[scottystills]

Just caught the same criss crossing leaves as in your last pic there. Of course I wasn't being diligent, just fixing some far worse carnage after my perches removed themselves from my frame hehe. Found my rears were ok, but the fronts were fairly loose. I've just now gotten in the habit of giving them a crank before I go wheeling each time, and I'm finding I'm getting up to 1/8 turn on each one each time. I'm sure that'll stop once they've stretched more, but I can see how they can loosen up fairly quick.

 

[Deuling]

I torqued them, then did it again after a few short trips. I've hardly been driving it though, so they went from tight to loose in under 50 miles.

That seems strange to me. I cranked down on mine and have been to the dunes mulltiple times and beat the crap out of my rig. And never did they get loose...


I dont go by a torque spec though. I tighten them until i cant get them to spin any more with a 3' breaker bar.....


May not be the correct thing to do, but ive never had one break or loosen up, and i did the front u bolts the same way.

 

[K85 Octane]

No antiseize, do it dry

And I don't know about using a 3' breaker bar, kinda overkill. Mine might be 20-24", unless it's cold.

 

[ktmoutfront]

I threw my u-bolts away, so I'm no help. But we have walked through the trucks on multiple trips, carrying a torque wrench and sockets, and asked the truck owners to check there u-bolts. 50% or so were not to spec.

 

[sponsoredbydad]

I had this happen too last season after playing with the spring packs. Torqued them to 180 twice and now seem to be fine. While it's all apart seems like a good time to lose those shims and weld on some new perches at the correct angle.

 

[Mastiff]

I had this happen too last season after playing with the spring packs. Torqued them to 180 twice and now seem to be fine. While it's all apart seems like a good time to lose those shims and weld on some new perches at the correct angle.

Yeah. A slip-yoke-eliminator is on my list, so the plan was to have that all dialed in at the right angle, or very close, so we'd know exactly where to weld them. I don't think I could get it right by predicting. I'll probably continue with that approach... just have to bit the bullet and buy the shims again.

I forgot to mention that the driveshaft bashed a huge dent in my muffler too.

Good question on why everyone didn't have to retight everything constantly on new trucks.

 

[NorCal_Chris]

Dan at Ruffstuff tells people to put an impact on em. And " tighten them till the impact gets tired"

 

[Mastiff]

ORD springs make it tough to take the load off since they have so much arch when unloaded. I used the engine hoist to pull up the frame since I didn't want to jack it to the moon from the axle in its current state. Hopefully I can drop the axle far enough with the wheels off to reinstall the center pins and shims.

Here's the muffler. The sheet metal behind the rear tire was sucked in about 4-5" but I pulled it out and you can't really tell. Still a bummer since the body was pristine.

 

[rampage]

ORD springs make it tough to take the load off since they have so much arch when unloaded.

Put a 4x4 between the spring eyes and a couple ratchet straps to compress the spring.

 

[Mastiff]

Put a 4x4 between the spring eyes and a couple ratchet straps to compress the spring.

Yeah, I did that during install. In this case the leaves are all crazy and need to be aligned to get the pin through. It _might_ still be possible, but the straps would have to stay to the outside to not interfere with the bottom leaves.

 

[paratrooper307]

Why isn't this a problem with new vehicles? When my dad bought his 89 Blazer the dealer never said 'And by the way, after the first 100 miles and after every off-road excursion, you need to come see us so we can check to see if your u-bolts are still tight'.
Are the factory u-bolts different from the aftermarket?

I'm guessing because new vehicles don't use shims. I used the DIY4X shims as well, and one of the side effects is that the spring is angled, therefore so is the top spring plate. This can result in the nuts not tightening down completely square on the plate. You'll have to torque them considerably tighter than factory recommendations, or the differing forces applied will be suceptible to loosening the nuts as the forces of driving act on the axle. I had to re-torque mine periodically after the initial install. Now I check them once a month.

 

[70jimmy]

The only slightly unusual thing I have going on is/was some thick shims (maybe 8*, I'll have to look it up in my email). They were good DIY4x ones though, with the flat spot for the center pin so it stays parallel. The head of the center pin is at an angle to the spring perch though. But I doubt that was a contributing factor.

I still can't quite imagine how the center pin broke and managed to completely disappear. And on both sides. I guess the U-bolts loosened and all the load was then on the pin. The head broke off, then just from rattling around it somehow went up and out. With one side flopping around, it surely sped up the demise of the other side.

Were the degree shims bolted to the leaf pack? I am not really familiar with DIY 4x ones, however the ones I had were bolted to the spring pack and had a recessed area that the head of the bolt fit into so it didn't stick out.