The DL10s were ordered in 1966 from Alco & MLW (4 from Alco, 6 from MLW) as replacements for most of the remaining class DL2 (RS-1) & DL3 (RS-2) locomotives. The railroad wanted some higher speed trucks (but not Hi-Ads) so all of these locomotives were delivered with lightweight GSC trucks.

Starting in 2021, the DL10s started going to ILW to be remanufactured with AC drivetrains & Cummins QSK38 prime movers. Half of the fleet was converted by 2023 when the program was paused so ILW could concentrate on new orders.

One of the TdM’s T-6s was taken out of service in 2022 because the TdM shops needed a new shop switcher instead of sharing ILW’s; this unit was rebuilt, replacing the 251-8 prime mover with a Cummins QSK23, then shuffling around the vents & plating over the marker light on the nose, but otherwise leaving it intact.

In 2024, the fleet was expanded by one with the purchase of Alco’s last Schenectady-built unit. It is earmarked for (eventual) display at ILW’s Schenectady works, but is currently in service on the TdM.

The whole fleet, including TdM A3, is in service, still, after 60+ years of service.