Check those Axle U-Bolts

[8e3k0]

Normally if the u-bolt assemblies are torqued the second and third time that is more than suffice (similar to wheels nuts). They should not become lose as all the u-bolts have had time to settle in and "find home" within the first few hundred miles of bumps, twists, and vibration. If you find that you have retorque a number of times and the nut needs another 1/4 or 1/2 turn; my concern would be that you have reached or passed the yield point of the bolt and simply stretched it to a point that it will actually snap. Tensile strength on a grade 5 bolt should be around 120,000 lbs per square inch (I think from memory). Remember those bolts are only a 1/2 inch diameter and a lot less at the root of the threads. On retorquing; if you find that the wrench clicks with no movement of the nut, the u-bolt assembly likely become stationary for the life of the system. This is then preventative maintenance. Ensure you have a good reliable torque wrench and use the same one each time with the rechecks. Ellis

[Tom S.]

Thanks Ellis!

[Jay Bird]

Good info. I will check mine tomorrow. Thanks

[bob]

Good info thanks . back axle loose

[KTManiac]

Just torqued mine down, with about 5,000 miles on the rig, and they were well under recommended values.

I would make the suggestion to those who are going to torque their U-bolts, to do them incrementally. Don't just crank one nut down to the final torque value, and then go on to the next nut, etc.

Set your torque wrench to a low value, say, 30-35 ft/lbs, and start tightening the nuts 1/16th-1/8th of a turn in a criss-cross pattern. Keep repeating the pattern until the wrench "clicks" on all four nuts. Bump up the wrench setting 5-10 ft/lbs and start all over again. Repeat until you reach your final torque value.

Set your wrench back down to the low value, and start all over again on the next U-bolt assembly.

[Jay Bird]

I just torqued my u bolts and they were well out of range except for two of them. The more you think you have a handle on things the more surfaces. Thanks Ellis. I am sure this info headed off a greater problem down the road. This will be on my pre trip check list from now on.

[8e3k0]

If you have retorqued and checked those u-bolts a couple of times from my experience of preventative maintenance, and the engineering field, I don't think you'll find that the bolts need anymore tighening; very similar to wheel bolt lug nuts. Still good to crawl under there once a year and simply check them both visually and with a wrench. Also gives you "peace of mind" that all is okay when your cruising at 60 plus miles an hour down a freeway. All suspension systems under RVs other than motorhomes are very light duty so constant visual checks are required to make note of anything unusal or parts breaking lose, also watch in the mirrors as to how your trailer follows; sides should be equal and straight on both sides. If you see more trailer in one mirror than the other when travelling in a straight line, you have the first indication of "dog Tracking" and axle misalignment. Ellis

[hookman]

I checked mine tonight and some where loose. It would good to check them at least once a year.

[lfw]

I checked my the other day.. I turned each one of them.. all 16 of them about 3 to 4 turns each.. My wife thanks you guy's for all the preventative tips you have... We love all the info on it..
lfw

[WorkerB]

Looking for a lost flashlight in the Monty I opened the hide-a-bed and spied a paper between the arm of the couch and dinette. I pulled it out and there were two documents. One explaining about brake maintenance complete with the torque values for my steel wheels and a service manual for leaf spring suspension also with torque values. My 2001 Monty 2850RK has AL-KO axles and leaf spring suspension. One document concerns leaf and shackle maintenance and has some interesting information. For instance it says that when tightening the 1/2" U bolt it should be tightened to a MINIMUM of 45 ft/lbs MAXIMUM of 60 Ft/lbs. Also Spring eye bolt should be tightened to a snug fit ONLY because "Parts must rotate freely". I have scanned both documents into PDF files. I don't know how to make these two documents available. I looked at photo bucket but looks like it's only for pictures. Suggestions? I just did a HD shackle upgrade and using an impact wrench I made everything TIGHT. I think I will go out this morning and loosen the spring eye bolts so I don't rip the hangers off the frame! Hope someone finds this information helpful.
John

[richfaa]

also watch in the mirrors as to how your trailer follows; sides should be equal and straight on both sides. If you see more trailer in one mirror than the other when traveling in a straight line, you have the first indication of "dog Tracking" and axle misalignment. Ellis"

That is exactly what alerted me that something was not right. The picture in the mirror just did not look right but it did not register what it was. We did pull into the next rest area and discovered our axle disaster.

[dsprik]

John, be careful. Those U bolts stretch - by design, apparently. If you release torque on those U bolts, then re-torque them to 50-60 lbs, you may stretch them to a point where you lose their tensile strength and break under minimal stress.

I don't know how much those U bolts cost, or how hard they are to install - maybe not bad one at a time - but you might want to consider new grade 5 U bolts to replace the ones over torqued. Especially if they were way over torqued...

[8.1al]

John,
If I remember correctly the spring eye bolts are shoulder bolts and are supposed to be torqued. It is possible to over tighten as Dave stated and stress the bolt but you can't tighten to the point that the spring eye is bound up.

[WorkerB]

HEY CHARLIE!
Good to hear from ya. Great wedding pics.
According to the user manual it calls for snug without torque values. They are shoulder bolts so when you hit the shoulder there is nowhere else to go. I KNOW they are more than snug cause when I was done with the job I hit every nut with the 1/2" impact.
Say hi to Nila for us.
Dsprik, I have not tightened my U bolts yet. I was talking about the bolts that go through the spring eyes. Concerning the U bolts. I was curious that some folks were concerned that they were getting 1/4 turn and more on the U bolt nuts. I thought maybe they were still in spec but at the low range of torque spec. Last year I spent $300 for an axle alignment and they checked everything. Wisdom says trust but verify. AGAIN information I have is for my vintage 2001 2850RK AL-KO suspension.
John

[dsprik]

After I posted, I had that brief thought (everything lately is a brief thought ) that you might have been referring to the eye bolt in your springs...

[hookman]

When I took my apprenticeship we where told that U-Bolts are not to be used more then once. So if you remove them from the springs replace them.

[Art-n-Marge]

It hasn't changed Hookman. No offense, but I estimate your apprenticeship was some years ago. I am working on my suspension and will be using brand new U-bolts and nuts. EVERYONE I talked to kept bringing up the fact not to reuse the U-bolts. Since I am adding an overload spring and spacer, the old ones won't fit anyway and will be donated to a recycle. The new ones being longer guarantee they will be new.

Thanks for the reassurance!

[Ozz]

quote:Originally posted by 8e3k0

Prior to our 450 mile trip last Friday afternoon, I though I would crawl under the Monty to check the torque of all 8 axle u-bolts. These are 1/2 in diameter and fine thread and takes a 3/4 socket to tighten. All 8 were basically in the lose state!! I used a standard half inch torque wrench and applied at least a 1/2 to 3/4 turn before torque specification was reached ( 65 foot pounds). I also find this quite interesting that, with this specification on a 1/2 inch u-bolt that tells me they are only equivalent to a grade 5 u-bolt ( 45 to 70 foot pounds torque) not grade 8 ( 100 to 120 foot pounds torque). Again compared to automotive industry, RV quality is lower. Tonight I am going to crawl under there again and retorque to see if there has been any change after our trip. I am sure that later on as we travelled without the retorque application we would have encountered a misaligned axle or even sheared the center bolt! I recommend to check the torque on all those axle u-bolts!! Ellis

Good post, worthy of a Bump.

[pbahlin]

This winter I replaced all of my round cross section U-bolts with the new ones that have a flat where they contact the axle. Torqued them all to 65 lbs. I just checked them today, for the first time, after 3500 miles, and every one was still at 65 lbs.

If you're in Indiana it's worth getting a set. They're not expensive and simple to replace. For me at least, they've held torque where my original ones never did.

[snow]

Thanks for the info...didn,t know you were suppose to check u-bolts for torque....mine is a 2007 Monty..never checked by me before....all we loose...2 and 1/2 turns on each nut to get to 60# torque.
Guess i,ll put this on the yearly maintance check. Thanks for the info, i never would have check.
My son, has a Coachman trailer...he broke the center bolt and axle shifted...noticed it backing into a campsite. Maybe his u-bolts were loose to start with.Once, he got it to a trailer place, they re-aligned the axle, new bolts...and u- bolts too...don,t need that problem if I can help it.
Okay, ready to go camping for Labor Day......have fun...

George & Joan Berlinger
Lapeer, Mi
2007 Montana 3075/ TrailAir Pin Box
2011 Chevy 2500 HD/6.6 Duramax
Allison, tranny/Husky/Valley slider hitch
1 Papillon/ spoiled rotten