The SD70M has a wide nose and a large comfort cab (officially known as the "North American Safety Cab"), allowing crew members to ride more comfortably inside of the locomotive than the older standard cab designs. There are two versions of this cab on SD70Ms: the Phase I cab, which was first introduced on the SD60M, and is standard on the SD80MAC and SD90MACs, and the Phase II cab, which is a boxier design similar to the original three-piece windscreen cab in the SD60Ms. The Phase II cab has a two-piece windscreen like the Phase I windscreen but the design of the nose is more boxy, with a taller square midsection for more headroom.
The SD70M is equipped with D90TR DC traction motors and the 710G3B prime mover. They are capable of generating 109,000 lbf (480 kN) of continuous tractive effort. From mid-2000, the SD70M was produced with SD45-style flared radiators allowing for the larger radiator cores needed for split-cooling. Split-cooling is a feature that separates the coolant circuit for the prime mover and the circuit for the air pumps and turbocharger. There are two versions of this radiator: the older version has two large radiator panels on each side, and the newer version has four square panels on each side. This modification was made in response to the enactment of the United States Environmental Protection Agency's (EPA) Tier I environmental regulations.
Production of the SD70M ceased in late 2004 as production of the SD70M-2 model began (the EPA's Tier II regulations went into effect on January 1, 2005). 1,646 examples of the SD70M model were produced. Purchasers included CSX, New York Susquehanna & Western (NYSW; part of EMDX order no. 946531), Norfolk Southern and Southern Pacific (SP); now part of the Union Pacific Railroad), but the vast majority were purchased by Union Pacific.