CAUTION! - Dexter Axles - Developing Trend?

**Cate&Rob** · 07-24-2018, 07:35 AM

Originally Posted by klenger

Has anyone found loose U-bolt nuts AFTER they previously torqued them to spec, or is this a one-time action? I'd rather not make this check again if I don't have to.

klenger - Same observation as Midwest Camper. See my posts 76 & 83 on this thread. Each re-torque requires less to regain original setting.

Rob

**BigGuy82** · 07-24-2018, 07:57 AM

OK. Just heard back from Grand Design. They thanked me for the information and said that it had been passed on to the VP of manufacturing to insure that it is not a problem area and for appropriate corrective action. They did read the information on the forum which was very encouraging. As far as I’m concerned with GD, mission accomplished - not much else they can say or do. I forgot to ask them if U-Bolt tightening is part of their required dealer PDI - my bad, but I'm pretty sure I know the answer. If anyone wants to follow up, please do and let us know.

Prior to this call from GD, I called Dexter and asked them about the U-bolts. Here’s their answers:

1. The axles and springs are assembled by Dexter and shipped to GD
2. The nuts on the springs should have been torqued to the “target” torque of 75 ft.lbs.
3. There is no way that paint, stretch, “settling in” or any other factor should have caused a loss of torque in excess of 50%
4. It is not abnormal to have a slight reduction in torque due to the above factors but he wouldn’t put a number on that. Again, he did agree that 50% was excessive in any case.
5. Conclusion: the cause was improper torqueing of the flange nuts or defective U-bolts.
6. Final actions: report this incident to the factory for follow up and replace all 12 U-bolts and 24 flange nuts. (his feeling on this was that it was likely a tightening issue but he wanted to use caution so he replaced the lot)
7. Dexter recommends checking all suspension components every 6 months/6,000 miles but no significant change in torque is to be expected.

Bottom line here is that I had a very real problem for whatever reason and it has been properly resolved. Hopefully, everyone learned a bit from my experience and research. Yes, it is wise to re-torque any nut/bolt in a critical duty application but the difference should not be this huge.

So that's it for me and I'm out of this thread unless it is to respond to any reactions about this particular post.

Safe travels.

**Canyonlight** · 07-24-2018, 08:13 AM

Originally Posted by Cate&Rob

From what I have seen on multiple GDRV Plant Tours . . . the frames arrive without springs or axles. Springs and axles arrive sub-assembled as shown in the LCI video. GDRV fastens the axle and spring assemblies to the clevis brackets on the frame. It is possible that they have changed this process to include assembly of springs to axles . . . but I doubt that they would want this complication in their final assembly process.

I would expect that your axles and springs came together at Dexter . . . although LCI and Dexter use the same springs.

Rob

Rob - does Dexter (or LCI for that matter) actually use torque wrenches or simply use air or electric impacts set to "X" ft-lbs. setting ? If so, what is the accuracy of these assuming the user has it set at the correct setting and is using it properly ?

Dan

**MidwestCamper** · 07-24-2018, 08:15 AM

Originally Posted by BigGuy82

OK. Just heard back from Grand Design. They thanked me for the information and said that it had been passed on to the VP of manufacturing to insure that it is not a problem area and for appropriate corrective action. They did read the information on the forum which was very encouraging. As far as I’m concerned with GD, mission accomplished - not much else they can say or do. I forgot to ask them if U-Bolt tightening is part of their required dealer PDI - my bad, but I'm pretty sure I know the answer. If anyone wants to follow up, please do and let us know.

Prior to this call from GD, I called Dexter and asked them about the U-bolts. Here’s their answers:

1. The axles and springs are assembled by Dexter and shipped to GD
2. The nuts on the springs should have been torqued to the “target” torque of 75 ft.lbs.
3. There is no way that paint, stretch, “settling in” or any other factor should have caused a loss of torque in excess of 50%
4. It is not abnormal to have a slight reduction in torque due to the above factors but he wouldn’t put a number on that. Again, he did agree that 50% was excessive in any case.
5. Conclusion: the cause was improper torqueing of the flange nuts or defective U-bolts.
6. Final actions: report this incident to the factory for follow up and replace all 12 U-bolts and 24 flange nuts. (his feeling on this was that it was likely a tightening issue but he wanted to use caution so he replaced the lot)
7. Dexter recommends checking all suspension components every 6 months/6,000 miles but no significant change in torque is to be expected.

Bottom line here is that I had a very real problem for whatever reason and it has been properly resolved. Hopefully, everyone learned a bit from my experience and research. Yes, it is wise to re-torque any nut/bolt in a critical duty application but the difference should not be this huge.

So that's it for me and I'm out of this thread unless it is to respond to any reactions about this particular post.

Safe travels.

They are flat out wrong on line three. We can go down the I did this and for how long path but I'm qualified to make this statement. It would be best for us to slow down and solve the mystery rather than to rush to a conclusion. I do not have a ton of faith in GDs phone tech support or any axle manufacturers support line for that matter. Its very possible that your axle was mis-torqued at Dexter but these bolts do stretch. 50% is very unlikely under normal use. I've also been digging and called the spring shop where I purchased my U bolts to get a better understanding in why Lippert and Dexter calls for such low torque values. They tell me they have had a bunch of trailers come in with broken springs where the U bolts were too loose. He could not remember the trailer brand but confirmed they were all Dexter axles.
Also he was surprise at how low the torque values are from Dexter and especially Lippert. I mentioned I could go up in torque but I'm concerned about bending the axle tube. So why do these manufactures use such low initial torques?
Here are some on-line specification on torque versus size and grade. It appears based on the tensile strength and yield strength that my OEM 9/16-18 u bolts were grade 5. The regular size nuts on the supplied U bolts are also odd. My replacement U bolts are grade 8 with deep nuts.

https://www.boltdepot.com/fastener-i...ed-Torque.aspx

**Cate&Rob** · 07-24-2018, 08:24 AM

Originally Posted by Toes in the water

Rob - does Dexter (or LCI for that matter) actually use torque wrenches or simply use air or electric impacts set to "X" ft-lbs. setting ? If so, what is the accuracy of these assuming the user has it set at the correct setting and is using it properly ?

Dan

Dan - If you watch the LCI video that I linked in post 81, you get a quick glimpse of the digital read out board just after the pictures of the four head torque gun. I know from working with these in the past that the operator would get an alarm if all four nuts did not individually reach the correct torque. This assumes that the tool was used and was working correctly.

Rob

**Cate&Rob** · 07-24-2018, 08:32 AM

Jim (MidwestCamper) - I suspect you are on to something with the U Bolt tension specified by Dexter and LCI having to do with the wall thickness of their axle tubes. Note that torque spec increases with axle size/capacity and does not reference U Bolt diameter. It would be interesting to compare the axle tube wall thickness of a truck axle to the tube thickness of these trailer axles.

Rob

**BigGuy82** · 07-24-2018, 08:34 AM

Originally Posted by MidwestCamper

They are flat out wrong on line three. We can go down the I did this and for how long path but I'm qualified to make this statement. It would be best for us to slow down and solve the mystery rather than to rush to a conclusion. I do not have a ton of faith in GDs phone tech support or any axle manufacturers support line for that matter. Its very possible that your axle was mis-torqued at Dexter but these bolts do stretch. 50% is very unlikely under normal use. I've also been digging and called the spring shop where I purchased my U bolts to get a better understanding in why Lippert and Dexter calls for such low torque values. They tell me they have had a bunch of trailers come in with broken springs where the U bolts were too loose. He could not remember the trailer brand but confirmed they were all Dexter axles.
Also he was surprise at how low the torque values are from Dexter and especially Lippert. I mentioned I could go up in torque but I'm concerned about bending the axle tube. So why do these manufactures use such low initial torques?
Here are some on-line specification on torque versus size and grade.

https://www.boltdepot.com/fastener-i...ed-Torque.aspx

An RV dealer, a Ford dealer, a truck spring shop (that's their main business - springs), Dexter, me and Grand Design all seem to think that #3 is not only correct - it is dead on the money. The point here is that I believe I have gotten to the bottom of my problem, so I'm happy. I will install the new U-Bolts, re-torgue them a few days later and then walk away for a year, at which point, I'll check them again and expect little or no change. This is pretty much my experience on four RV's (well, three - I never checked the springs on my Class A). If you can learn from my experience, great. If you choose to continue pursuit of this matter, I encourage you to do so.

**MidwestCamper** · 07-24-2018, 09:09 AM

Originally Posted by Cate&Rob

Jim (MidwestCamper) - I suspect you are on to something with the U Bolt tension specified by Dexter and LCI having to do with the wall thickness of their axle tubes. Note that torque spec increases with axle size/capacity and does not reference U Bolt diameter. It would be interesting to compare the axle tube wall thickness of a truck axle to the tube thickness of these trailer axles.

Rob

Thanks Rob,
And the trucks use a cradle under their axles which will allow for higher initial torques. This may be another case where the trailer industry barely or sometimes cannot meet a safety factor of 1. Sad.

**minnow101** · 07-24-2018, 09:10 AM

It seems to me the maximum torque value is only as good as the weakest component. Why is the torque value so low compared to spring hardware on a pickup; is it the trailers u bolts, nuts or axle tube that is designed so poorly that anything over 50 ft. Lbs. (or so) will strip the u bolt or nut or crush the axle?

Certainly one can replace the u bolts and nuts with grade 8’s but if applying 90 ft. Lbs. crushes the thin axle tube then what has been accomplished?

Until someone much smarter than me can answer that question, I think the only prudent course of action is to continue to check and re torque the u bolts on a regular basis.

**MidwestCamper** · 07-24-2018, 09:21 AM

Originally Posted by BigGuy82

An RV dealer, a Ford dealer, a truck spring shop (that's their main business - springs), Dexter, me and Grand Design all seem to think that #3 is not only correct - it is dead on the money. The point here is that I believe I have gotten to the bottom of my problem, so I'm happy. I will install the new U-Bolts, re-torgue them a few days later and then walk away for a year, at which point, I'll check them again and expect little or no change. This is pretty much my experience on four RV's (well, three - I never checked the springs on my Class A). If you can learn from my experience, great. If you choose to continue pursuit of this matter, I encourage you to do so.

Dick, Curious...in previous posts you have mentioned your sailuns make your rig ride rougher than the original ride quality. Are the sailuns an upgrade from your original tire and are you running the recommended tire pressure listed on the yellow tag on your Solitude?