| 1 | TTDX | Trailer Train Co. | added 1/1967; 10/1968-1/1980; eliminated 1/1992 | | NAKINA |
| 2 | TTDX | TTX Co. | added 1/1992; 1/1994-7/2005 | | NAKINA |
| 3 | TTDX | Trailer Train Co. | added 1/1967 | | NAKINA |
| 4 | TTDX | Trailer Train Co. (FMS flat cars specifically equipped to carry military vehicles semi-saddleback) | 10/1968 | | NAKINA |
| 5 | TTDX | Trailer Train Co. (flat cars, equipped with 16 tie-down winches with chains and bridge plates; for transporting military vehicles semi-saddleback style) | 4/1970-1/1980 | | NAKINA |
| 6 | TTDX | Trailer Train Co./TTX Co. (flat cars equipped with 16 tie-down winches with chains and bridge plates; for transporting military vehicles) | 7/1985-1/1994 | | NAKINA |
| 7 | TTDX | TTX Co. (flat cars equipped with 16 tie-down winches with chains and bridge plates; for transporting military vehicles, equipped with end of car cush.) | 7/2000 | | NAKINA |
| 8 | TTDX | Trailer Train Co. | added 1/67 | | NRHS |
| 9 | TTDX | Trailer Train Co. (FMS flat cars specifically equipped to carry military vehicles semi-saddleback) | Oct-68 | | NRHS |
| 10 | TTDX | Trailer Train Co. | Apr-70 | | NRHS |
| 11 | TTDX | Trailer Train Co. (flat cars, equipped with 16 tie-down winches with chains and bridge plates; for transporting military vehicles semi-saddleback style) | 1/75-1/80 | | NRHS |
| 12 | TTDX | Trailer Train Co. | eliminated 1/92 | | NRHS |
| 13 | TTDX | TTX Co. | added 1/92 | | NRHS |
| 14 | TTDX | TTX Co. (flat cars equipped with 16 tie-down winches with chains and bridge plates; for transporting military vehicles) | Jan-94 | | NRHS |
| 15 | TTDX | TTX Co. (flat cars equipped with 16 tie-down winches with chains and bridge plates; for transporting military vehicles, equipped with end of car cush.) | Jul-00 | | NRHS |
| 16 | TTDX | TTX COMPANY {TRAILER TRAIN COMPANY} | | | PWRC |
| 17 | TTDX | Trailer Train (TTX Corporation) | | | RSRV |
| 18 | TTDX | TTX COMPANY | | | SCAC4 |
