quote:please enlighten me with the inconsistency in that locomotive designation...DD35A is correct...but, not DD40AX?
First and foremost, try to NEVER use the term "consistent" when discussing ANYTHING related to EMD product designations!!!
Now, the DD35 model came out first (1964), designed specifically for the UP. Later on (1965) the UP liked the DD35 so much, the requested EMD furnish DD35s with cabs, thus EMD simply added a GP35 type cab to an EXISTING MODEL, and the DD35A was built and delivered.
By 1967/68, the UP still wanted/needed bigger and higher HP units, and EMD Engineering Department was developing what would become the "Dash 2" line of locomotives. Therefor a completely new model unit was developed for the UP with the new "experimental Modular Control System". Thus the DDA40X was born as a "new model", i.e. the new full width nose & cab arrangement, 645F series prime mover at 3300HP for traction, and the experimental modular electrical control system; accounting for the "X" designation at the end of the model DDA40 designation.
