I think the formulas in this discussion are incorrect as they do not take into account the weight on rails. Using the formula TE = HP*308/Speed a GP40-2's TE is as follows:
3000*308/11.1 = 83243.243243243
BUT an SD40 which weighs much more and would have greater weight on the rails is:
3000*308/11= 84000 and since an SD40-2 weights about 100000 lbs more than a GP40-2 the calculations do NOT work.