big66440 Posted July 16, 2018 Share Posted July 16, 2018 Can I re use my U bolts holding the leaf springs to my axle? I’ve heard you’re not supposed to do that, if so why not?. I’m planning on replacing my leaf spring bushings. Link to comment Share on other sites More sharing options...
DirtyComanche Posted July 16, 2018 Share Posted July 16, 2018 They're torque to yield, no go on reusing them. Basically they stretch out permanently each time you torque them, and they're only meant to do that once. I had a ubolt break and just about kill me in the ensuing chaos. I ranked the experience as about a 0/10. Link to comment Share on other sites More sharing options...
Eagle Posted July 16, 2018 Share Posted July 16, 2018 https://www.eng-tips.com/viewthread.cfm?qid=256363 Link to comment Share on other sites More sharing options...
HOrnbrod Posted July 16, 2018 Share Posted July 16, 2018 I've always read that the primary reason u-bolts should not be reused is because of the u-bolt threads. They are rolled, not cut. When torqued, the rolled threads are distorted. This thread distortion will not allow the proper torque to be maintained after the nuts have been loosened, removed, then reinstalled and re-torqued. Link to comment Share on other sites More sharing options...
Eagle Posted July 16, 2018 Share Posted July 16, 2018 This is looking more and more like one of those situations where everyone "knows" it shouldn't be done, but everyone has a different reason. What I know: I have reused factory u-bolts on several vehicles, including my race car back in the 1970s, without having any problems There must be dozens of people who have done the added main leaf AAL budget boost in XJs, and I'd bet that none of them bought new u-bolts The new u-bolts I see in the parts stores look to be 3/8" or 7/16", max, and I'm sure they're made in China. MJ factory u-bolts are 14mm (.5512", which is close to 9/16" - .5625"). I would much prefer to take my chances with used 14mm u-bolts than play around with Chinese replacements that are of questionable steel, and smaller to begin with. Link to comment Share on other sites More sharing options...
JeepSchmidt O'Guinness Posted July 16, 2018 Share Posted July 16, 2018 Eagle, what's your stance on Renix era vs the HO Chrysler era u-bolts, OEM of course? Link to comment Share on other sites More sharing options...
Jeep Driver Posted July 16, 2018 Share Posted July 16, 2018 No, it's a situation whereas you do what you want because no matter what anyone says, they are wrong. I had mine made, grade 8, 9/16, deep nuts. Heavy truck repair shop that made the Ubolts recommended that I torque to 80lbs. The bolts will not yield before they crush the tube of the 8.25 rear, mine are at 70lbs. I've reused mine three times. You buy BS Chinesium bolts............well................ Do what you want, save the arguing. Link to comment Share on other sites More sharing options...
DirtyComanche Posted July 16, 2018 Share Posted July 16, 2018 35 minutes ago, Eagle said: The new u-bolts I see in the parts stores look to be 3/8" or 7/16", max, and I'm sure they're made in China. MJ factory u-bolts are 14mm (.5512", which is close to 9/16" - .5625"). I would much prefer to take my chances with used 14mm u-bolts than play around with Chinese replacements that are of questionable steel, and smaller to begin with. Go to a spring shop and have them make a set of 9/16" ubolts. Link to comment Share on other sites More sharing options...
Eagle Posted July 17, 2018 Share Posted July 17, 2018 19 minutes ago, DirtyComanche said: Go to a spring shop and have them make a set of 9/16" ubolts. Been there, done that. I keep a half dozen sets around, some sized for the D35 and some for the D44. Link to comment Share on other sites More sharing options...
cruiser54 Posted July 17, 2018 Share Posted July 17, 2018 I have never replaced a u bolt except when I needed longer ones. Been reusing them for 50 years with no issue. But, they were never rusty, and I liberally sprayed the threads with some kind of penetrating oil before removing the nuts. Link to comment Share on other sites More sharing options...
HOrnbrod Posted July 17, 2018 Share Posted July 17, 2018 13 hours ago, Eagle said: Been there, done that. I keep a half dozen sets around, some sized for the D35 and some for the D44. Factoids: The factory MJ u-bolts and nuts are as follows: U-BOLT 52002885, 4 Standard Duty *** 52003996, 4 Heavy Duty 11500756, AR NUT The Standard Duty u-bolts are shorter and used for the standard 3+1 leaf springs. Heavy Duty u-bolts are longer and are used for the heavy duty MT 4+1 springs. The u-bolt nuts are the same size for both style u-bolts. Thus there is no difference in the u-bolts except length between the D35 and D44 axles. Also the rear shock nuts and u-bolt nuts are the same. Link to comment Share on other sites More sharing options...
AZJeff Posted July 18, 2018 Share Posted July 18, 2018 On July 16, 2018 at 11:42 AM, Eagle said: https://www.eng-tips.com/viewthread.cfm?qid=256363 Being a retired mechanical engineer, I found that little discussion really interesting, and it backs up the "rule of thumb" stuff we have all heard about U-bolts on leaf springs. Link to comment Share on other sites More sharing options...
schardein Posted July 21, 2018 Share Posted July 21, 2018 I've often wondered why U-bolts can't be reused, but wheel lug studs generally last the life of the vehicle and will certainly be re-torqued multiple times. Link to comment Share on other sites More sharing options...
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