The McClure Volcker act (sounds like that) makes the dealer have to prove anything that you've done to your truck is the cause of a break down. Hanging better skid plates, sliders, and steel bumpers isn't going to effect the transmission, fuel system, or radio - anything effecting those other things and a hundred more aren't the fault of a modification. About the riskiest thing I've done warranty wise is changing the factory air cleaner for one that can be cleaned and reused (K&H). The VQ engine is what - two decades old - and appears in the top ten engines every year, year-after-year. The biggest risk I see others doing is modifying their lift extensively and wheel size beyond factory sized. The lift changes the angles between the transfer case and differentials. The larger wheels and tires add rotational mass which is going to load up the drive train beyond the stock engineered numbers. The folks back east get happy on the skinny petal playing in the mud and they have a far higher insistence of differentials exploding.
I've added lots of modifications to the truck and have zero worry about my warranty. Warranty covers shopping malls ... not Death Valley, the Bradshaw Trail, and Mojave Road.
If you follow the main runs of the club you'll find that we're pretty concerned about our daily drivers and aren't out to violate the warranty nor pile up body, frame, and suspension damage. I've made two or three dozen runs in the last four years and have tore open one tire sidewall (covered under America Tires' warranty!) on a rock, broke two sway bar mounts ($12 part) on the Mojave Trail, two mud flaps (first run!) on Rattlesnake Canyon, and my worst was blowing one of the factory strut ($70 which I had been driving over stressed for two years on lift springs) near Bell Mountain. In return I have made dozens and dozens of friends and toured places you only see in the movies or in documentaries.
You bought a rugged 4WD truck for a reason, you paid several thousand dollars more for the stronger suspension and drive train ... now have fun with them.