Rear Axle U Bolt Retorquing

lindenengineering

Well-known member
Membership of the wheel tappers and shunters club that is!
Some seem to be moving over to the key tappers and paper shufflers:thumbdown: GRRr, trying to keep their Lilly whites (hands) clean!:lol:

I am seeing large propensity of Sprinter rolling into the shop with LOOSE REAR AXLES and wallowed out spring perches with damaged rear springs in many cases.

This can be easily be detected in its early days and remedied if you would get back into the wheel tappers club (its free) and check the U bolts with hammer and shunt some new U bolts under there when needed.

Just simply tap the U bolt with a hammer!
If its tight it will ping!
If its loose it will make a thunk sound.

Taken directly from WIS this morning the torque U-bolts as follows


[B]SPRING U- bolt on rear axle spring to rear axle M14X1.5 Nm 160 Model 906.6/7[/B]


[B]Rear spring U-Bolt to rear axle m14X1.5 Model 904./5 690.612/613.904 Nm 170[/B]


So:
NVC3 - 118 foot lbs torque for the 2007 and up Sprinters and
T1N - 125 ft/lbs for the 904 or 2001-2006 Sprinters.

Hope that helps a bit.
If its rusted in place it MUST be freed off and re-torqued !

Torque pattern here: https://sprinter-source.com/forum/showpost.php?p=546761&postcount=35

Dennis
 
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220629

Well-known member
Re: Membership is declining.

Somewhat random, or is there any correlation with model years or miles?

vic
 

Brokecanadian

2005 Cargo 2500 SHC NA
Re: Membership is declining.

That's never been a thing on any of my American vans; I'll give it a try

Tightening until the bolts started to deform worked on my Ford

Sent from my STV100-3 using Tapatalk
 

SprinterTeck

Gray hair tech
Re: Membership is declining.

That is something that it states to do one the 1st PM according to the sheet from Benz, however I make sure to re-torque them on every PM here at Coke. We do Pms every 7,500 miles. So far we have never had any issues of this. I have found several times the bolts do need a few degrees before the torque wrench "clicks"....
 

sprint2freedom

2008 NCV3 170ext
Re: Membership is declining.

Is this simply a matter of jumping under there and retorquing, or does the rear suspension first need to be unloaded?
 
D

Deleted member 50714

Guest
Re: Membership is declining.

Refer to Mercedes-Benz document AP32.20-D-3271H for details on recommended re-torquing procedures.

General note: On older vehicles, I would recommend several applications of Gunk brand Liquid Wrench or equivalent rust penetrator on nut and threads common to u-bolt the day prior to retorquing. Especially, vehicles operated on salt Roads.
 
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israndy

2007 LTV Serenity
Re: Membership is declining.

If it's rusted in place do you NEED to retorque it? I hope to drive this thing into the ground 10,000 miles a year. Hopefully it will take many more years.

-Randy
 

Mike DZ

2016 View 24V (2015 3500)
Re: Membership is declining.

Got underneath my rig today and put the torque wrench to my rust free U bolt nuts ... On passenger side I got to 125 ft lbs after 5-10 degrees of rotation, on driver's side some nuts took 25-30 degrees. I was surprised as the rear axle had been replaced by an official MB dealership with Sprinter mechanics about 5000 miles ago. The axle replacement was an attempt to resolve the drone/howl noise and was not related to an axle or spring problem.

I wonder if it was mechanic induced or the nuts had backed off that far in 5000 miles. I had planned on re-torquing in another 10K miles, but glad I did it now. Thanks for the heads up, Dennis.
 

SprinterTeck

Gray hair tech
Re: Membership is declining.

Taken directly from WIS this morning the torque U-bolts as follows


[B]SPRING U- bolt on rear axle spring to rear axle M14X1.5 Nm 160 Model 906.6/7[/B]


[B]Rear spring U-Bolt to rear axle m14X1.5 Modle 904./5 690.612/613.904 Nm 170[/B]


So 118 foot lbs torque for the 2007 and up Sprinters


and 125 ft/lbs for the 904 or 2001-2006 Sprinters. T1N.

Hope that helps a bit.
 

SprinterTeck

Gray hair tech
Re: Membership is declining.

Also I soak my bolts in Kroil at start of the PM and after the test drive and pm complete, I will loosen and re-torque the nuts and as of yet, (knock on wood) we have never seen or had a problem.
 
D

Deleted member 50714

Guest
Re: Membership is declining.

Got underneath my rig today and put the torque wrench to my rust free U bolt nuts ... On passenger side I got to 125 ft lbs after 5-10 degrees of rotation, on driver's side some nuts took 25-30 degrees. I was surprised as the rear axle had been replaced by an official MB dealership with Sprinter mechanics about 5000 miles ago. The axle replacement was an attempt to resolve the drone/howl noise and was not related to an axle or spring problem.

I wonder if it was mechanic induced or the nuts had backed off that far in 5000 miles. I had planned on re-torquing in another 10K miles, but glad I did it now. Thanks for the heads up, Dennis.
I Have enjoyed years of torquing/retorquing things. Like the time I was handcuff officer on a cell extraction team. After hours of failed negotiations resulting from an inmate holding his cell door food/tray port hostage by refusing to allow officers to close and lock the port. An extraction team was assembled comprised of about six officers called a "stack." Each officer has a specific task as follows and in order; shield officer, baton officer, handcuff officer, leg irons officer, back up officer and video camera officer. My task was to apply handcuffs by "torquing" the inmates arms behind his back. It didn't sound like he enjoyed the unintentional over-torquing.

Back on topic: Torque is a generic term describing practice of stretching a fastener to a specified value. There are various methods to measure fastener torque. I have employed them all. While working on the space shuttle, lasers were used to measure fastener "stretch" the most accurate method accomplished by measuring the length of the fastener before and after "torquing."

In the case of retorquing of the U bolts, torque is measured by measuring fastener rotational resistance. As a result, it is imperative fasteners requiring torque be absent of corrosion and lubricated. Additionally, prior to retorquing, it is necessary to untighten the fastener as enumerated in Mercedes-Benz document mentioned in post12.

I don't think the nuts have "back-off" or loosened. The nuts appear lose because the U bolts have stretched from operating stress. Wait... I see you had your rear-end replaced. In your case, the components may have settled-in or the technician used the calibrated elbow method to tighten the nuts insufficiently.

Bob
 
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sprinterPaul

Well-known member
Re: Membership is declining.

What does that document say about loosening? From prior posts most dealers if they remember to do it. Just go in and crank tighter. Thanks!

I Have enjoyed years of torquing/retorquing things. Like the time I was handcuff officer on a cell extraction team. After hours of failed negotiations resulting from an inmate holding his cell door food/tray port hostage by refusing to allow officers to close and lock the port. An extraction team was assembled comprised of about six officers called a "stack." Each officer has a specific task as follows and in order; shield officer, baton officer, handcuff officer, leg irons officer, back up officer and video camera officer. My task was to apply handcuffs by "torquing" the inmates arms behind his back. It didn't sound like he enjoyed the unintentional over-torquing.

Back on topic: Torque is a generic term describing practice of stretching a fastener to a specified value. There are various methods to measure fastener torque. I have employed them all. While working on the space shuttle, lasers were used to measure fastener "stretch" the most accurate method accomplished by measuring the length of the fastener before and after "torquing."

In the case of retorquing of the U bolts, torque is measured by measuring fastener rotational resistance. As a result, it is imperative fasteners requiring torque be absent of corrosion and lubricated. Additionally, prior to retorquing, it is necessary to untighten the fastener as enumerated in Mercedes-Benz document mentioned in post12.

I don't think the nuts have "back-off" or loosened. The nuts appear lose because the U bolts have stretched from operating stress. Wait... I see you had your rear-end replaced. In your case, the components may have settled-in or the technician used the calibrated elbow method to tighten the nuts insufficiently.

Bob
 
D

Deleted member 50714

Guest
Re: Membership is declining.

What does that document say about loosening? From prior posts most dealers if they remember to do it. Just go in and crank tighter. Thanks!
Standby while I retrieve the document.
 

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D

Deleted member 50714

Guest
Re: Membership is declining.

The best I can do is take photos. Talk about Germans and minutia. Jack vehicle, Scribe existing "clocking"of not relative to the saddle/perch, loosen nut approximately 45 degrees to overcome "static friction." Re-torque ensuring nut returned to our beyond scribe point. Damn. Oh snap! This all has to be individually performed in sequence!
 

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D

Deleted member 50714

Guest
Re: Membership is declining.

What does that document say about loosening? From prior posts most dealers if they remember to do it. Just go in and crank tighter. Thanks!
.........And the reason why I like to preform all my preventive maintenance. Time is irrelevant, Quality paramount! I am the only one trustworthy enough to ensure the work is done in accordance to the minutia enumerated by Mercedes-Benz publications.

I want my vehicles to operate reliably at optimum performance. That's why I am in this forum, studying, learning and understanding. Then, if it is necessary I take my vehicle to the dealer I will be informed, knowledgeable and not easily hoodwinked by unscrupulous carpet baggers!

Stay hydrated!

Bob
 

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