I have the 40 mph front diff vibe with Bilstein 5100s set at 1.75" I lowered it to .85" and that reduced the vibe a lot, but it was still there. I couldn't stand the look of the truck, so I raised it back to 1.75" and just live with the vibe. I honestly don't notice it that much since switching to D load rated AT tires. The tire noise and ride seem to drown out the front diff issues. I may try the replacement front bushing that they are working on and see if that helps get rid of the vibes.