Original post by: Troy ,
Most diffs are angled or tilted back so the welded seam isn't true centre of the diff. I just went through all this on an 2008 kw w900l with 8 bag suspension. Same symptoms. Measure from centre of wheel or hub to the ground. Then measure from bottom of frame rail to the ground. Subtract the two numbers and this will give you your ride height at true centre of the axle. Make sure you do all this at the rear axle on a kw. It has been suggested that the axle with the leveling valve is where you measure Made my kw ride like a dream. All my rough riding issues went away. Shifts like a dream. Vibrations went away. And tire wear is more even too as too low or high adjustment will throw your camber out a bit on your tires. Never knew a kw with 46,000lbs rears and an 8 bag suspension could ride as smooth as it does. Hope this helps. Most dealers if they aren't being jerks will give you the proper ride height value. On my truck it was 10.5". That's was the most clear and easiest explanation I finally got on how to do this properly. Again.....if your diff is angled....the welded seam is not true centre of the axle. Also if you have 2 leveling valves you have to get them even.