Shackle bolt break

[Wileykid]

Add another bolt break. Didn't want to add in the other current thread.

Coming back from a 2,300 mile trip yesterday, I noticed in my mirror, that I could not see the left rear of my trailer, that it appeared to not be tracking properly. Pulling off the road, looked underneath the trailer, and you can see the spring off the bolt. To tell you the truth, other than the tracking, the Summo springs made it almost like there was no problems. There was a truck/trailer repair place about three miles from where I pulled off, and they were able to get a bolt into it, and I drove the last 130 miles home. The trailer has about 14,000 miles on it, and the bolts are greased several times a year. Looks like the weld broke, and if you look at the picture of a bracket that is still good, only about half the weld is actually doing anything. I will contact GD on Monday, but my current thought is getting the trailer to a commercial trailer repair place and have them check all the other bolts, fix the issue, and make sure the alignment is good.

[StephenO]

I don't really have much to add, but I thought it would be worthwhile adding the link to the other thread for future reference. When doing Wiki pages, I try to include cross referencing to make searching easier.

Other thread on broken bolt thread
https://gdrvowners.com/forum/operati...tting-ready-to

[Jlawles2]

Wileykid The Angle iron between the vertical members should only be welded on one side to the vertical then on the opposing side to the other vertical. This appears to be how they are installed based on the middle picture of the first row (looking forward weld on left outside) and the 3rd on the first row (looking rearward inside).

[Wileykid]

Wileykid The Angle iron between the vertical members should only be welded on one side to the vertical then on the opposing side to the other vertical. This appears to be how they are installed based on the middle picture of the first row (looking forward weld on left outside) and the 3rd on the first row (looking rearward inside).

You are right. I could not really get a picture of the weld on hanger (opposite side) where the bolt failed, but it looks like the weld failed only because of the bolt breaking and the twisting of the hanger.

[ajg617]

Wileykid The Angle iron between the vertical members should only be welded on one side to the vertical then on the opposing side to the other vertical. This appears to be how they are installed based on the middle picture of the first row (looking forward weld on left outside) and the 3rd on the first row (looking rearward inside).

Mine was tack welded on the opposite side as confirmed by the GD Mobile tech that replaced both rear hangers. There were deep wear points on the end of the original 'hardened' bolts on my front springs at the ends where the bushings were damaged and the spring eyes enlarged beyond repair. The knurled ends were also worn flat. So now this makes 5 recent events - all with 8K axles but build dates a year apart or more. For anyone keeping track,
2022 376THS
2022 310GK-R
2021 398M
2021 320G
2021 349M

Link here. https://gdrvowners.com/forum/operati...tting-ready-to

[Wileykid]

Was at the trailer repair place today, and they found that the right rear wet bolt was also broken. It was still in, no idea why it had not worked its way out. The original was the left rear. They are currently, at my request replacing all the wet bolts with the nylon bushing and solid bolts. Should get it back tomorrow.

You can see the bolt snapped in half cleanly at the grease hole.

[Country Campers]

Wileykid
Could you please post clear pictures of the ends where the break is?

Brian

[Wileykid]

Wileykid
Could you please post clear pictures of the ends where the break is?

Brian

The second picture is the bolt joined back together. The fit really well, as clean break.

[Jlawles2]

If possible can you clean the end of the bolts and try to get a better up close picture. It's a bit hard to tell, but it almost looks as if the bolts are too hard (brittle fracture). I'm not a materials expert by any means. but knowing what created the issue could help pinpoint the solution.

Image showing the difference:


And not being a straight across break does not necessarily indicate one or the other.

Also fracture through the grease hole is expected due to location (about center between the supports) and the forces being the highest in that area, reduction of material (gross area), and the stress riser effect due to the sharp corners in the holes. (That is a trip down memory lane from 30 years ago).

[Cate&Rob]

x2 on Jlawles2 Joseph’s theory. I was in the process of writing exactly the same thing . It would be ideal to get a hardness measurement of the break. A bolt should bend or stretch before it fractures . . .

Rob

[Scott'n'Wendy]

A bolt should bend or stretch before it fractures . . .

Rob

A grade 5...yes. A grade 8...no. A cheap no name bolt?.....who knows.
I need to crawl under the trailer and look at the bolt heads. This breaking at the grease hole is getting me worried. Like it never reportedly happened through the 2010's...but starting to happen now?

[Wileykid]

A grade 5...yes. A grade 8...no. A cheap no name bolt?.....who knows.
I need to crawl under the trailer and look at the bolt heads. This breaking at the grease hole is getting me worried. Like it never reportedly happened through the 2010's...but starting to happen now?

So far, it seems to be primarily on the 8K axles.

[Wileykid]

Here are the pictures. Hopefully what you are looking for. The middle one is the one that the spring bent the bracket and slipped off the bolt.

[Jlawles2]

Yeah that's a good set of pictures. It almost looks like brittle fracture starting at the exit of the grease hole spanning across to the raised section where it starts transitioning into a ductile failure.

The interesting thing would be to know the orientation of the bolt in the spring. If the hole was at the top, that would be one of the highest tensile stress areas depending on how much stress the springs put pushing outward during loading.

[AlexPeterson]

Here are the pictures. Hopefully what you are looking for. The middle one is the one that the spring bent the bracket and slipped off the bolt.

This looks like classic fatigue failure from multiple cycles of stress. The "beach marks" are the visual clue of progressive crack propagation. These trailer axles generate enormous side loads when we turn on pavement, the maximum being a tight turn of course. 5th wheels can be turned tighter than bumper tow, so they can see the most sideways skidding. Watching from behind when someone is making a tight turn is alarming. The amount of distortion is easily visible between front and back axles. I suspect that proper mechanical engineering stress analysis isn't part of the frame design in the spring hanger area. It should be.