New bolts with new leaf springs?

[Hoginedgewood]

I'm ready to order beefier leaf springs. 2700 to 3400. I think I've seen where the front bolts are not reusable. 
are 1 year old bolts shot?  What about the U bolts?

[kylant]

leaf spring bolts are fine to reuse. 

u-bolts should be replaced. generally u-bolts are single use. they "stretch" when torqued. 
however, when my rear axle had to be replaced (twice) the dealer reused the factory u-bolts,  said they were fine

[newdude]

14 hours ago, Hoginedgewood said:

I'm ready to order beefier leaf springs. 2700 to 3400. I think I've seen where the front bolts are not reusable. 
are 1 year old bolts shot?  What about the U bolts?

 

 

Service manual shows only the front mounting bolt as a one time use stretch bolt so replace them.  

 

Order two new ones.  Everything else is reusable so u-bolts, nuts and the rear shackle bolts are all listed as reusable.  11602394 is the bolt you need.  

[Grumpy Bear]

12 hours ago, newdude said:

 a one-time use stretch bolt so replace them. 

 

 

From a metallurgical standpoint I find this fascinating. A fastener stretched into the plastic zone is toast. Into the elastic limit it is reusable. Hense elastic. Once past elastic and now plastic, is has been compromised. Unstable and unreliable. 

 

Sounds like a place ARP makes a living. 

 

The Official ARP Web Site | Technical Information (arp-bolts.com)

[Another JR]

Torque to yield bolt installation designs are used in critical tension-loaded bolts where consistency of the clamping force or uniformity of the clamping force for a set of bolts is critical. Engine head bolts, transport aircraft wing root joints, and aircraft engine mounts are some of the places I’ve seen it used.  Typically you torque to a particular high level and then rotate the fastener a specified additional amount. With these designs you are just into the beginning of the yield range with no significant necking down of the bolt section.  If you went too far it would be unreliable, but the installation using torque plus angle ensures you don’t cause excessive yielding. 
 

With all that written, though, I strongly suspect the requirement to replace this bolt if removed is not because it’s been torqued to yield.  First of all, it’s a shear loaded bolt not a tension loaded bolt, so why would the designer consider torque to yield at all. Second, the torque spec I found for the nut is 148 ft lbs. with no additional angle to be turned. Finally, I think that size bolt would require more than 148 ft lbs to yield. 
 

Instead, I suspect the bolt has to be replaced because it uses some kind of single use torque retention feature like deformed threads to keep it from loosening and coming out causing a hazardous loss of axle control. 

Edited August 7, 2023 by Another JR