Do U-bolts move on the axle tubes?

[SSROSS]

I just received a whole axel assembly from Dexter this week to replace a bent axel on my rig. There were two computer generated stickers on each end with the torque numbers for the bolts, they were 1/2 inch bolts and were torqued to 75 foot lbs. You must re-torque them after 500 miles and it wouldn’t hurt to check again after another 500 miles. No way should those bolts be loose on your axel and they should fit tight around the axel.

 

[Tom Traveler]

Totally agree with Hoopy and others - nothing on that part of the suspension should be moving at all. In my opinion U bolts should exactly match the diameter of the axle tubes. If there is slop, I don't believe you can properly torque the U bolts as the U bolt will bend and flex trying to conform to the axle.

Edit: went back to re-read your OP and need to scratch what I said about U bolts matching the axle tube diameter. Still agree with others though that nothing should be moving or sliding on those axle tubes.

Ok, now I'm confused again. Why would you scratch what you said? U-bolts should exactly match the diameter of the axle tubes. I've been looking at leaf springs on cars, trucks, trailers, etc. for 60 years and the space between the U-bolt arms always exactly matched the diameter of the axle tubes.

 

[roegs01]

Ok, now I'm confused again. Why would you scratch what you said? U-bolts should exactly match the diameter of the axle tubes. I've been looking at leaf springs on cars, trucks, trailers, etc. for 60 years and the space between the U-bolt arms always exactly matched the diameter of the axle tubes.

Sorry for the confusion - I totally agree that U Bolt arms should exactly match the diameter of the axle tubes. I edited my post as I originally thought that GD had sent the OP larger U Bolts. I realized that was not the case when I re-read the OP post. I'll go back and edit my original edit.

 

[ajg617]

I'm a bit confused. What is the difference between "1/2 in. U-Bolt" and 1/2 in. U-Bolt/Hex Nut? Don't all U-Bolts have hex nuts on them? What does the Min 70 to Max 80 torque spec apply to? Wouldn't it be to the hex nut on the threaded portion of the U-Bolt? If so, what does the Min 45 to Max 70 apply to?

View attachment 48104

And hence my confusion. And to top it off the 1/2" u-bolts GD sent with the 8K axle kit were too small to fit around the diameter of the Dexter tube. So there's at least another set of measurements and torque values. Apparently LCI has 9/16" u-bolts and 90 ft lbs for their 8k axle kits - guessing they are the ex-Curt axles.

 

[Hoopy Frood]

Some 8,000 lb. rated axles are 3.5 inches in diameter and the U-bolts are 9/16". It not too unusual to see a range for torque settings, especially something like U-bolts. For example wheel lug nuts usually are a range, maybe 90-120 lb. ft. I usually figure to hit it in the middle.

 

[Scott'n'Wendy]

You must re-torque them after 500 miles and it wouldn’t hurt to check again after another 500 miles. No way should those bolts be loose on your axel and they should fit tight around the axel.

The lack of retorquing is, IMO, the source of a lot of axle issues. A lot of people know to retorque a wheel after a week or so. Almost nobody checks their trailer u-bolts. But they should. At least during the first year. Once when they get it, once after 100-500 miles, and once at the end of the season. Most will be fine. Some of you will be scared just how loose they are.

 

[ajg617]

The lack of retorquing is, IMO, the source of a lot of axle issues. A lot of people know to retorque a wheel after a week or so. Almost nobody checks their trailer u-bolts. But they should. At least during the first year. Once when they get it, once after 100-500 miles, and once at the end of the season. Most will be fine. Some of you will be scared just how loose they are.

Wish I had known. So should I loosen if necessary and reset the U-bolt positions for those that are not properly aligned? I'm sitting leveled on a concrete pad but with some weight on the wheels.

 

[ajg617]

It should be a 3/4" socket/wrench. Shoot for 70 lb.ft, that's the min, or the max. Should be good. But really need to see if those U-bolts are actually loose, or if they just look that way.

I just went back and looked at the spring positioning. Hard to tell if it's the angle, but they do look to be not square on the spring perch. I'll have to check mine out tomorrow and see if they are square.

Tight - no movement at all even with a hammer. And, my bad - they are 9/16" U-bolts 3.5" tube. GD says set torque to 90 ft lbs and carry on. I'm going to replace them with the proper dexter ones when I get home.

 

[JCR GD]

Wish I had known. So should I loosen if necessary and reset the U-bolt positions for those that are not properly aligned? I'm sitting leveled on a concrete pad but with some weight on the wheels.

Yes, if not aligned properly they can move/loosen.

 

[Casa_Woody]

And the nuts should be tightened down evenly, in stages. When complete, there should be equal thread sticking out above each of the nuts.
If done improperly, the U-bolts will not be clamped to the axle properly and things can shift.

 

[dryfly]

I'm really interested in this as well. The "min" reading of 45 to the "max" of 70 is a lot different spread than the other 2 readings for a 1/2" U-bolt. We may need to call Dexter on this one.

 

[Hoopy Frood]

Well, I just went out this morning and torqued my U-bolts down to 75 ft.lbs. They all tightened up a bit, but no indication that the U-bolts have slipped on the axle. Everything looked hunky-dunky.

 

[SSROSS]

If you go on to Dexter’s site they show how and in what sequence to torque u-bolts and what torque settings for each bolt size.

 

[Scott'n'Wendy]

Wish I had known. So should I loosen if necessary and reset the U-bolt positions for those that are not properly aligned? I'm sitting leveled on a concrete pad but with some weight on the wheels.

Yes. They need to be perpendicular, not at an angle. And as previously posted by Ken, tightened down evenly with equal amount of thread showing beyond each nut. Within a couple threads at least. Then when you move to the next CG, check the torque again.
FYI, the u-bolts with the flattened radius are a higher quality u-bolt in my experience.

 

[ajg617]

Well going by the receipt these are actually 9/16" 3.5" tube. Torque is 90 ft lbs. These were torqued to 95 by installer - called him today.

 

[RetiredWeR]

A couple of those pictures looks like the spring center bolts weren’t in the alignment hole in the spring saddle. Thus allowing the axle free movement. The angle of the u bolts suggest that they may have been tightened but never torqued hammered and torqued again.

 

[IBEW Sparky]

They should not move. If they did, the wheels would loose alignment, braking would cause the axles to rotate, who knows what else?!

The axles can't rotate from the u-bolts being a little bit loose... There's a wedge plate welded onto the axle between the u-bolts.

 

[Scott'n'Wendy]

The axles can't rotate from the u-bolts being a little bit loose... There's a wedge plate welded onto the axle between the u-bolts.

I'll say they can...a little bit....then that stresses it a bit and makes it a little more loose....and over time.....

A little loose always...eventually...becomes a lot loose.

 

[ajg617]

A couple of those pictures looks like the spring center bolts weren’t in the alignment hole in the spring saddle. Thus allowing the axle free movement. The angle of the u bolts suggest that they may have been tightened but never torqued hammered and torqued again.

Well everything is tight so I don't know what to say. I had a long half inch breaker bar and couldn't budge the nuts either way. There is no gap between any of the perches and the lower springs so I'm assuming the pins are in the holes.