When the lb7's first came out GM was recommending changing out rear axle fluid after first 500 miles (yes five hundred). So many people complained about this that they just dropped the recommendation. This is according to the dealer I bought mine from, who told me to do it. I did it at 500 and again at 50,000, and the magnet was noticeably cleaner the second time.
2004 lb7 Cali. emissions ECLB 2500 HD. Tows 12K lb. 5th wheel.
Injectors replaced at 49K miles (Jan. 2012).
EFI Live by Idaho Rob with Edge Insight CTS and pyro.
Fumoto drain valve and stainless bleeder screw from Merchant.
Bilstein 5100's from Norcal Nick.
Prodigy P3 brake controller.
Transynd, Mobil Delvac and Stanadyne PF.