made to accommodate the new HT-C truck design, in which the traction motors all face the same direction, making the trucks longer. After a series of derailments involving Amtrak SDP40F units that were equipped with "hollow bolster" HT-C trucks, applied only to the SDP40F, Conrail ordered the SD40-2 units and several orders of SD50s with the older Flexicoil trucks, but the HT-C truck was vindicated and it ultimately went under most 40 Series, 50 Series and 60 Series six-axle locomotives, and this truck is still found under many remanufactured locomotives. Some SD45 and SD45-2 units have been modified by replacing their 20-cylinder engine with the 16-cylinder removed from scrapped SD40-2 units; this was common on Union Pacific and possibly other railroads. In many cases these are identified by the owner as SD40-3, SD40M-2 or some such. Confusingly, what appears to be an SD45 is labeled as an SD40-2. Older SD40-2 units used in low-power modes such as yard switching or hump service have been de-turbocharged, resulting in the mechanical equivalent of a SD38-2. Units so modified may or may not be re-labeled. There are several variations of the SD40-2 such as the SD40T-2s (Informally: T for tunnel motor; the actual EMD designation is "SD40-2 With Cooling System Modification", as stated on this model's EMD manuals) bought by the former Southern Pacific, and Denver and Rio Grande Western railroads; now operated by Union Pacific. The SD45 tunnel motor equivalent, the SD45T-2 model, was also utilized by Southern Pacific. Many tunnel motors were rebuilt and sold second-hand to a handful of American shortlines including, Bessemer and Lake Erie, Illinois Railway and Missouri and Northern Arkansas, as well as Canadian shortline Goderich-Exeter Railway. There is the SD40-2W (W for the 4-Window Safety Cab) bought and operated by the Canadian National railway. High-nosed versions of the SD40-2 were bought by Norfolk & Western, & Southern Railway. These units are now operated by the Norfolk Southern Railway (Resulting merger of N&W and Southern Railway). A narrow gauge version produced for Ferrovia Central Atlantico in Brazil is the BB40-2. Three cabless SD40-2Bs were also rebuilt from standard SD40-2s by the Burlington Northern Railroad in the early 1980s. The units had been in collisions and BN decided that it was more economical to rebuild them without cabs. Canadian Pacific also owns a few SD40-2Bs. These were created by welding metal plates over the cab windows of many