Leaf spring U bolts torque spec

RustyRatRod said

The reason they are only 45 is to allow the springs to slip in the spring plates as the suspension compresses and rebounds.

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I doubt that. I suspect 45 ft-lbs was determined by the factory to be sufficient in preventing a loosening of u-bolt nuts and/or decoupling of the spring, spring plates, and perch. A higher torque could/would crush the axle tube.

But maybe RustyRatRod has a reference. I'm interested.