difference between SD75M and SD75I

what is the difference between the two? is it the cabs or something else?

Cabs I think...M is for widecab (on EMDs) and the I stands for Isolated cab (it's quieter inside). There's probably other differences, I just don't know them.

i just did some research and the only railroad to purchase the SD75M was Santa Fe (#200-251), in March of 1995 (shortly before the merger) with 51 units, wheras the newer SD75I was purchased by BNSF (#8251-8275), in December of 1995 with 25 units, another order in October of 1997 (# 8276-8301) with 26 units, and Canadian National bought 175 SD75I's (#5626-5800) between May 1996 and May 1999.

Joe

That's right! I don't know of any other differences between the two. You can tell the isolated cab from the gasket visible around the nose, which isn't present on the M cab.

Ontario Northland has also purchased SD75I's in small numbers.

Yup. You can have an "M" cab without an "I" cab but there is (at this point) no such thing as spartan "I" cab. The "I" designation was short lived though and is no longer used...for example the last batch of SD90MAC Phase 2's and the Long Island DM and DE's all have isolated cabs but no "I" in their designation. As info, the new SD70ACe and SD70M-2 units are NOT isolated cabs although that could change per customer requests.