As the light branches were abandoned or rehabilitated, the bulk were upgraded with new fuel tanks and Flexicoil B-B trucks and assigned to yard and transfer service. In 1988/89, 39 GMD1s were remanufactured by CN as GMD 1Us, 12 emerged with B-B trucks and continued to run long-hood-forward, while the others retained their A1A trucks and were converted to shorthood-forward operation.[2] On April 19, 2021, CN's last GMD-1 was retired from revenue service.[3]
A number of GMD1 units were sold off in the 1990s and 2000s to rebuilders, leasers, regional and shortline railways. Twenty were acquired by Ferrocarriles de Cuba.[4]Oregon Pacific Railroad acquired CN No. 1413, and is now numbered OPR No. 1413.[5]Cando Rail Services acquired CN 1401, 1434 and 1435 in late 2018. CN 1401 is now CCGX 1009, CN 1435 is CCGX 1010. Waterloo Central Railway took donation of and restored a GMD1 in 2021.[6]