I would strongly recommend trading the entire axle. That way they will never know that you tampered with anything during the warranty period. I think that your drivetrain warranty goes out further than the "bumper-to-bumper" warranty and it covers your differential if you haven't altered it.
Since we all have the same bolt pattern and disc brakes I would swap the whole axle.
Galaxy Black 2004 Titan XE CC 4x4 w/ Off-Road Package, Preferred Package.
Mods: PRG Spacers, 17x9" Eagle 187s (+2mm offset) w/ 315 70-17 BFG All-Terrain KO tires, Stillen Diff Cover, Alpine Type-R components in the front, coax. in the rear w/ 50 x 4 Rockford Fosgate Amp, XM, Debadged, and Homemade RCA pre-outs on in-dash changer.