U bolts rear axle

[Jean-Marc L'Eplattenier]

2019 2500HD Duramax diesel. What is the OEM spec for the rear axle leaf spring u-bolts? I am installing longer shackles to drop the rear. I have seen so many different answers on other posts.

[paauto]

On 11/20/2019 at 6:10 PM, Jean-Marc L'Eplattenier said:

2019 2500HD Duramax diesel. What is the OEM spec for the rear axle leaf spring u-bolts? I am installing longer shackles to drop the rear. I have seen so many different answers on other posts.

If you are only putting drop shackles on, you shouldn't need to loosen/remove the axle U Bolts.  In any case, the U Bolts, nuts and washers are torque-to-yield single use, so if you loosen or remove them you should technically replace them.  The sequence for tightening the bolts is as follows (do it in an X cross pattern) (i) first pass: 74 lb ft (ii) second pass: loosen 270 degrees (iii) third pass: 74 lb ft (iv) final pass: 180 degrees.

 

The bolt that connects the shackle to the spring should be torqued to 129 lb ft.  Not exactly sure what the torque spec for the shackle to the frame is, but I know the spec for the bolt that holds the front of the spring to the frame is: (i) first pass: 125 lb ft (ii) second pass: 90 degrees.  

 

Also, you should torque things with the weight of the vehicle on the ground (i.e. don't torque things with the axle hanging down free or when the weight of the vehicle is dropped on it, the bushings will bind and wear out prematurely.

 

Hope this helps.