Mach number temperature generally decreases with increasing altitude between sea level and , the speed of sound also decreases. For example, the standard atmosphere model lapses temperature to at altitude, with a corresponding speed of sound (Mach1) of , 86.7% of the sea level value. While the terms "subsonic" and "supersonic", in the purest sense, refer to speeds below and above the local speed of sound respectively, aerodynamicists often use the same terms to talk about particular ranges of Mach values. This occurs because of the presence of a "transonic regime" around M = 1 where approximations of the Navier-Stokes equations used
Ford Mustang Mach 1 rear axle was optional, and the 428 CJ/SCJ included a "traction lok" with a 3.91 or 4.30 ratio, 31 spline axle shafts and a nodular case. In 1970, the 3.91 ratio was a "traction-lok", while the 4.30 ratio was a Detroit Locker. Mach 1s came with upgraded suspension to varying degrees dependent upon powertrain choices. Big block cars had front shock tower reinforcement, thicker sway bars (no rear bar for 69), and heavier springs and shocks. 428 CJ/SCJ 4 speed cars also came with staggered rear shocks. Standard on Mach 1s was a fierce but cosmetic hood scoop that had