They can only void certain parts as they pertain to the lift...springs, struts, control arms, etc. If your radio stops working they'd have to somehow prove that your lift caused it...good luck! So basically your dealer doesn't know too much about the warranty or they just want the extra $$$ they make when doing "non-warranty" repairs.
Do a search on the "Moss-Magnussen Act." It requires that dealers must prove that your modifications caused the damage before denying warranty work. Make sure the dealer knows you are aware of this law and often they change their minds.
