it will not void your warrenty.. They have to prove without a doubt that this lowering caused a problem in your warrenty. It the Moss-Magnuson (?msp) Act. Something close to that. I have had alot dome to my truck and i have checked just to make sure... sometimes it has to do with the dealer, just show him that Act, and he cant say nothing about it. I have had absolutely no probs with that.... Later...
Oh and btw look in my gallery to see my tranformation.. Just getting the shorter shackles is worth it.. Get them from S1S - Slammed1.. My rideability increased and i wasnt bouncing all over the place when i hit bumps in the rear. Huge difference, then i suggest you to get new shocks, anything is better than stockers.... Get the Nitro Active, or better yet the Bilsteins... Later...