Adjusting the Torsion Arm When Changing Tire Size on 2004 Duramax Diesel

I purchased a 2004 GMC Duramax recently that the previous owner put 285/75R16 tires on. I would like to go back to the original 245 tires but am wondering if the previous owner also tweaked the torsion arms as well. Is there a way to tell if they have been adjusted or some way to put them back to the factory settings. Thank you for your help, Rick. With 285/75R16 tires it is very likely that the torsion bars have been adjusted at some point in the life of the truck – otherwise they would rub pretty hard. You can make a quick visual determination of torsion bar height by looking at the lower control arm jounce rubber. A stock height front suspension will just start to squish the jounce rubber sitting at static height. If there is any gap at all, the torsion bars have been adjusted up. So, how do you adjust the torsion bars to allow the front suspension to sit at stock height?...

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Joel Paynton is an award-winning GM technician who specializes in Duramax fuel systems. He also does custom programming for any GM powertrain. Visit him on the web at


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