My job is a warranty claims administrator and auditor. Trust me, the dealership has no say in this, they just report what they see.
Your entire warranty can not be voided, but the drivetrain portion can, just as the suspension portion or audio portion can be for mods to those systems.
And if you want to fight a voided warranty, you usually can't do it in small claims court, because the value of the warranty is higher than the limits in most states for small claims court.
I will also add, don't waste your money, and don't plan on winning. Not to be rude, but I have yet to see anyone win to get it reinstated. I've seen denied claims get overturned, but never a voided warranty get "unvoided".
While the law is that the dealer or manufacturer must prove the part is what contributed to the failure, that isn't going to help you. It is CAKE for them to prove this. And their lawyers can usually cite legally accepted precedent so they won't have to have an expert testify.
I will add though, if you win a case in court for a denied repair, the manufacturer or insurance company of that manufacturer will usually have to pay your legal fees.