So as many of you know I did my X and modified B code spring swap a few weeks ago and could not be happier with the ride. However I was back under my truck yesterday to replace some bushings and wanted to check on my springs again, specifically my new U-bolts. I got out my 1/2" drive torque wrench to check on the torque on all of the bolts and found that my U-bolt torque was about 50 ft/lbs all the way around, front and rear. So I re-torqued all of the U-bolt nuts to the recommended settings of 100 ft/lbs for the front and 165 for the rear. I will however, be checking these again in the near future for tightness and will apply some loc-tite if they continue to loosen up. I think most U-bolts are torque to yield bolts and therefore do stretch some which I think is what occurred here. So if you have recently done a spring swap I highly recommend you check your torque values after a few hundred miles of travel.

 

the thing with torque to yield bolts is once you torque them to stretch them, you can't retighten them and maintain the same amount of stretch... it will stretch them more. I'm not sure it really matters on things like U bolts but it does on head bolts.

I'd suggest using nylon locking nuts on U bolts...

 

Did you originally torque them with all the weight of the ex on the ground?

I also re-torque at 100 miles and checked again at 1000 miles. I may have gone 10lbs at 100 and nothing at 1000.

Good info!