The newer Viper T6060 2008-2015 uses ATF+4. It is an automatic transmission fluid but is now used in gearboxes and power steering systems for many Chrysler products. This thin oil is good for ease of shifting and it has a friction modifier
additive that improves shear strength.
From 1992-1997 the T56 Transmission in the Viper used Dexron 3 automatic transmission fluid. They changed to Castrol Syntorque 75w85 lubricant in 1997 because of complaints of neutral gear rattle. The camshaft change on the new Gen 2 engine had a lumpy idle, which rattled the mainshaft in transmission at idle with the clutch in, resulting in a sound that was like a bunch of marbles in a tin can. The thicker oil dampened the noise and corrected the complaint.
A side effect of the new oil was a little heavier shifting (more so in the cold) and longer lubricant life (the ATF would not hold up to the heat and require more frequent changes).
John Dontao, retired driveline development engineer for Team Viper and owner of Donato Racing Transmissions suggests the Syntorque in all applications, including racing.
Hope this helps.