Check those Axle U-Bolts

[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

[firetrucker]

Thanks for that tip. I'll add that to my checklist under the 6 month check.

Bob

[tspoon]

I'll add that to my right now check list.

[simonsrf]

Just recently in the shop that I bought the new axles, a big sign there said that they will not reuse the u-bolts. They make them there and they charge for them too.

[richfaa]

Humm.. That is the probable cause I suspect for our sheared center pin and resulting axle shift... Glad we are going to the Mor Ryde IS suspension and doing away with all that stuff. Mor Ryde did re torque all our U-bolts.

[sreigle]

Thanks for the headsup. I just put that on my list to do the next reasonably cool day or the day prior to departure, whichever comes first.

[Crossthread]

According to the Dexter manual,it's odd that they have such a spread on the torque specs for the u bolts, 45 to 70 lbs . Bill

[Lawman]

Thanks, added to my "do" list.

[Sinterior]

Thanks! We have an '09 too, and I'm going to check them before our snowbird trip this coming winter.

[Art-n-Marge]

Well, I'll just go check mine tomorrow. I'll report what I find just for comparison sake. With a 45 to 70 ft lb range I will split the difference and tighten them to 60 ft lbs. Thanks for the headsup, 8e3k0!

Stay tuned.

[8e3k0]

Did a recheck on mine last night and set them at the upper end, after the 450 miles or so of relatively rough road they were all in the 65 to 70 foot pound area. Also did a check on bolt torque specs and with dry conditions and not lubricated a grade 5 fine thread bolt can be torqued to 90 foot pounds. I suspect that because they are U-bolts and will likely stretch more than a straight bolt they lower torque levels. Gives me a higher comfort level now; would hate to see my axles leave the Monty!!!

[Art-n-Marge]

Well now, 8e3k0, I followed your lead and found that the passenger side ubolt nuts were all torqued at 65 except for one, but only required one or two few short turns of the wrench before I got the reassuring click.

I can't say the same for the drivers' side. They needed almost the same number of many turns on ALL the bolts except one - I didn't check specifically but I don't even think they were at 40 lbs. Some were real bad. I wonder if a different person torqued the driver side over the passenger side at the factory.

My gratitude for the great tip!!!

[Fire5er]

Thank the Lord for this forum and the good people on it! Because of you guys I went out and check our U-bolts this morning, before our two week vacation trip of 800+ miles, and sure enough they were all lose. Most took over one full turn before I got a 65 ft lbs click.

[Tom S.]

quote:Originally posted by 8e3k0

Did a recheck on mine last night and set them at the upper end, after the 450 miles or so of relatively rough road they were all in the 65 to 70 foot pound area. Also did a check on bolt torque specs and with dry conditions and not lubricated a grade 5 fine thread bolt can be torqued to 90 foot pounds. I suspect that because they are U-bolts and will likely stretch more than a straight bolt they lower torque levels. Gives me a higher comfort level now; would hate to see my axles leave the Monty!!!

You are right, axle bolts do stretch, which is why spring shops won't reuse them.

[8e3k0]

I was quite surprised that the actual u-bolts are of the grade 5 quality or lower with the recommended torque spec. Majority of automotive u-bolts are of grade 8 or better with higher torque specs. Would want to make sure that the stretch of the u-bolt does not pass its yield point and fail. Good old mechanical engineering and metalurgy facts.

[Art-n-Marge]

Using less quality U-bolts makes NO sense to me on a vehicle (Monty) that is by average per axle DOUBLE the weight over a vehicle. With all the bouncing and jostling going on, it's got to be more stress than a car or truck so it makes NO sense why they would go with something weaker.

Unless, the RV industry banks on the aftermarket dollars from repairs and replacements even for collateral repairs when something breaks.

[Tom S.]

I am guessing the reason they can use Grade 5 bolts is there is not as much torque on the axle. Car and trucks axles must fight the same road conditions the trailers do, but they also have to fight the torque created by the engine/drive train. The only torque trailer axles see (other than when we park) is braking.

[richfaa]

So much to learn.... So much to learn....This has been educational thread.

[embraceatrend]

Most of mine took a half to a full turn to get to 65 foot pounds, thanks for the tip, good post, keep em coming.

[Tom S.]

OK then! Did mine today. Three were tight, the remaining ones took anywhere from a 1/4 turn to nearly one full turn to tighten up. As I mentioned, these bolts do stretch, so I wonder if they are now seated for good or if they will need re-tightening. May be someone close to a spring shop could ask them. The one near us closed years ago.