The DL23 class are an ILW rebuild – to C-636 specs – of a fistful of used C628s purchased from the Chicago & Northwestern after being retired from iron ore service. They served for many years on the D&H before electrification swept them off the system, and then they were scattered around various Parsons Vale routes that are still not electrified.

While they were serving on the D&H, most of them went through Colonie to have their high short hoods cut down; by the time the electrification was finished only 3 (683,688,700) still had their original N&W high nose.

In the mid 2010s (after 30 years of service for some of them) the Parsons Vale sent most of them off to ILW for another rebuilding; this time to “C-635"s with a Cummins QSK78 prime mover and all AC electricals. The C-635s are, despite having less horsepower, considerably more powerful engines than the C-628ms because their AC motors are much less prone to wheelslip. (Where 3 C-628ms were needed, 2 C-635s can do the job.)

The C-628s are odd centuries out due to their tri-mount trucks. By the end of the 2010s, some of their trucks had worn past the point of safe repair, and the TdM shops started a project of retrucking them with trucks from scrapped MLW M-type locomotives. 4 of these units were retrucked in 2022 before the project was cancelled in favor of trying to fit radial trucks instead.

As of 2027, all of these locomotives remain operational; 10 are on the OC, 3 are on the EP&NJ, and the remaining 9 have been assigned to the LT&L to operate on the ex-CPR mainline between Toronton & Montréal. 8 of the OC units are currently stored pending retrucking or retirement, and the 4 units that were successfully retrucked are operating on the LT&L. The three remaining high-nosed units are marked for donation to railway museums, while the rest are scheduled for remanufacturing with radial trucks and continued service on the dieselised sections of the railway..