One of the things often neglected is lubrication of the transmission, transfer case and differential. As with the automatic transmissions there are now dozens of specified lubricants that a professional shop must have available. What used to work no longer does, and putting the wrong lube into a late-model unit will result in spoiling a good rebuild. You must use the correct fluid for the unit you are working on. It sounds logical, but if you understand why, it will go a long way toward preventing shift complaints and outright failure under warranty due to incorrect lube fill.