1. Advance Adapters’ Atlas four-speed transfer case has a solid one-piece 356-T6 aluminum main case with an underdrive unit providing more gear reduction. There is a 2:1 reduction gear in the main case and a 2.72 planetary unit from an NP271 Dodge T-case. The Atlas is an all-gear, no-chain transfer case with helical-cut gears. The four-speed T-case has 32-spline front and rear 1-3/8-inch output shafts standard. This case was ordered with a standard tailhousing, but short tailhousings are available, along with both driver- and passenger-side front-drive outputs. This case’s gear reduction combinations are 1.00:1, 2.00:1, 2.72:1, and 5.44:1, though lower gears are available. The Atlas four-speed has shift-on-the-fly capability, which means you can go from 2WD to 4WD at speed, and shift between reduction gears (changing gear ratios) at 5 mph. Each Atlas transfer case is hand-built and stamped with a serial number that allows Advance Adapters to recall all the history of any Atlas transfer case.