Do U-bolts move on the axle tubes?

[ajg617]

Follow-up to our issue with wet bolts, missing bushings, ruined springs and shackles. We put about 1,000 miles on since springs, shackles, wet bolts, and U-bolts were replaced. Today we pulled in to Salina and when I pressed hitch height, heard a metallic clanking sound coming from the suspension as the front lifted. Same was heard when I auto leveled. Tried both again and same noises but I can't tell from which side (sounded like both). So, the U-bolts that GD sent were not the correct size and wouldn't fit around the axles (pic of old and wrong U-bolt below) so the local trailer repair was able to source form a shop that custom makes them. The original U-bolts were flat on the bottom - the wrong replacements and the locally sourced replacements are completely round and not flattened.


I crawled under and there are no broken hanger welds, no broken or missing bolts, everything is greased and is in place. The only thing I can see is that the U-bolts appear to be moving on the axle tubes themselves where they surround the bottom of the tubes. Given that the axles tubes are not perfectly straight, I'm assuming that something has to move as road loads change. Is that a wrong assumption?

 

[Hoopy Frood]

I agree that things move around some, but, IMO, one of those things SHOULD NOT be the U-bolts! If they are moving, something is loose, and should be thoroughly investigated before further travel. JMO of course.

Did those U-bolts come off the same axle?

 

[Rabbit]

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

 

[ajg617]

I agree that things move around some, but, IMO, one of those things SHOULD NOT be the U-bolts! If they are moving, something is loose, and should be thoroughly investigated before further travel. JMO of course.

Did those U-bolts come off the same axle?

No. The new were sent to me by GD along with new springs, shackles, wet bolts. Wrong size. The older one with the flattened bottom is an original. The new sourced replacements (non-GD/Dexter/LCI) look exactly like the wrong size that GD sent - just larger in diameter to match the original. I can see two that are not perfectly aligned on the axle tubes (i.e. spread apart at the round ends by more than the distance between the bolt ends). I'm wondering what the torque value should be and if the replacement local sourced u-bolts are the correct hardness.

 

[Hoopy Frood]

"Not perfectly aligned on the axle tubes". I'm not sure I understand this, at least my poor brain is having trouble with it. I believe the torque value for mine was 50-60 lb.ft. I think the hardness of the U-bolt shouldn't be an issue unless they over torqued the nuts.

 

[ajg617]

Maybe some pics will help. Right rear, right front, left rear, left front. Note the marks on the axle tubes - might have been from the old u-bolts not sure. But appears RF and LF are spread further apart at the tube end then at the top bolt/nut end.

RF RR

LF LR

 

[Hoopy Frood]

Wow, that sure doesn't look kosher to me. It does look like on of the U-bolts has moved, and that definitely should not happen. Have you checked the torque on the nuts yet? Have you tried tapping the bottom of the U-bolt over to see if it's as loose as it looks?

 

[kb0zke]

I'm not an engineer, but it seems to me that a u-bolt should have the same distance between the two legs as the diameter of the axle it supports. If the distance between the legs is less than the axle diameter, something will have to give. Either the legs will expand, in which case the legs won't fit the perch, or the axle will be bent, which is likely to weaken the axle.

I would suggest that you take that original u-bolt and find eight that match all of the numbers (length, width, strength, etc.) and replace the old bolts with new.

 

[ajg617]

Wow, that sure doesn't look kosher to me. It does look like on of the U-bolts has moved, and that definitely should not happen. Have you checked the torque on the nuts yet? Have you tried tapping the bottom of the U-bolt over to see if it's as loose as it looks?

Not sure I have the correct socket - job for tomorrow. But there are three choices for 1/2" U bolt torque according to the Dexter manual.

1/2" Ubolt 70min 80max
1/2" Ubolt/hex nut 45min 70 max
1/2" flange nut 70min 80max (I don't have a flange nut)

But can't tell which of the first two. The replacement 1/2" U-bolts sent for the 8K axle kit by Grand Design don't fit so that makes me wonder which is the correct value.

 

[ajg617]

I'm not an engineer, but it seems to me that a u-bolt should have the same distance between the two legs as the diameter of the axle it supports. If the distance between the legs is less than the axle diameter, something will have to give. Either the legs will expand, in which case the legs won't fit the perch, or the axle will be bent, which is likely to weaken the axle.

I would suggest that you take that original u-bolt and find eight that match all of the numbers (length, width, strength, etc.) and replace the old bolts with new.

Have an email into GD since they sent a set of U-bolts that are identical to the ones put on - just too small. Neither match the original set.

 

[CoChris-MGRV]

..... I'm wondering what the torque value should be and if the replacement local sourced u-bolts are the correct hardness.

From the Dexter service manual I looked up in 2018 for my Solitude 310GK;
Note: This was for my trailer. Check you bolt diameter and the type of nuts you have for your application.

Size & type: ½” diameter, flange nuts. ¾” deep socket
Torque: Dexter manual says 70~80 #-ft



Note: The U-Bolts nuts were WAY under torqued when I received the trailer. They were about 45 #-ft BREAKAWAY torque and one was 25 #-ft. There was a lot of compliance in the bolt system and it took a lot (in some cases almost a full turn) to get to 75 #-ft. I rechecked them every year to 70 #-ft and they have not loosened up.

I talked to my dealer. They were completely useless. No idea the proper torque (we just "do them until they are tight").
I talked to Dexter service & warrantee (574) 295-7888. They were very helpful. Said 75 #-ft was correct and recheck to 70 #-ft. Dexter said the correct parts (for my trailer) where Kit (2 U-bolts, 4 nuts) p/n K71-294-00 or U-bolt 011-017-01 and nut (single) 006-129-00 (or -01).

If you use the part numbers I gave, verify they are correct size for your axle tubes.

Chris

 

[ajg617]

I don't want to get stuck again - an extra week in Glacier and it looks like there is still an issue to be corrected.

 

[nprario]

Just curious are not the springs indexed into the perch by a pin on the bottom of the spring pack? If so I wonder how much play there is between the pin and the spring perch hole?

 

[ajg617]

Just curious are not the springs indexed into the perch by a pin on the bottom of the spring pack? If so I wonder how much play there is between the pin and the spring perch hole?

Yes. New spring picture below (GD sent me 6 of them). Makes me wonder how the spring alignment can appear to be off so much on at least one of the perches.

 

[Hoopy Frood]

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.

 

[ajg617]

From the Dexter service manual I looked up in 2018 for my Solitude 310GK;
Note: This was for my trailer. Check you bolt diameter and the type of nuts you have for your application.

Size & type: ½” diameter, flange nuts. ¾” deep socket
Torque: Dexter manual says 70~80 #-ft

Chris

I know I don't have flange nuts - just nut and washer. I'll call Dexter tomorrow but I'm really concerned that a couple of the perches are no longer centered on the springs and I don't know how that could happen.

 

[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.

Of course I brought 7/8 and 15/16 sockets - no 3/4. I'll tap with a hammer tomorrow morning and see if they move. I hope it was just the angle I took the pictures at otherwise I don't know how a pinned spring could be off center of the perch so much.

 

[Hoopy Frood]

^^^^^^^^^^Yeah, there's no way they should be moving, even a little bit.

 

[roegs01]

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.

 

[Tom Traveler]

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?