SD-40 vs SD-40-2

[Compressor man]

What modifications were made to the SD40 to make it into an SD40-2?

Thanks, Chris

[Ted Marshall]

Chris,

There are no significant, noticeable differences between the 1st and 2nd. generation SD40. The deal breaker is behind the panel at the rear of the cab... electronic microprocessors.

 

 

What modifications were made to the SD40 to make it into an SD40-2?

Thanks, Chris

[WSOR 3801]

Actually, there are a number of differences. 

SD40.

SD40-2.

Most SD40-2s (except Conrail) had the HT-C trucks.  All the traction motors face the same way, so it pulls better.  The older Flexicoil truck had one motor facing the other way from the other two, so under heavy load it could upset the balance and cause wheelslip.

The HT-C truck is longer.  To keep 4000 gallon fuel capacity, the frame was lengthened by about 3 feet.  This helps explain the long "porches" on either end of a SD40-2.  The same length frame was used on the SD45-2.  20 cylinders plus a longer non-flared radiator section fill the frame quite well.  

The nose might be a bit longer, especially later production ones, and those equipped with "snoot" noses, much longer to hold radio remote control equipment.

The Dash-2s have an overhang on the back of the cab, gives a little protection from rain.

The doors in the radiator area are a different configuration.  A sight glass is mounted on the engineer's side, so the water level can be checked without opening the doors (provided the glass is in good condition).

The engines and eletrical systems were upgraded quite a bit in the Dash-2 line, but those improvements are pretty much not externally visible.

There may be other differences, but those are the main ones.

[trainfan1221]

The best way to appreciate the size difference is to see them right next to each other.  The SD40-2 took most of the extra legnth on the back porch of the unit, making it a somewhat unbalanced looking beast.  The SD40 looks a little more normal, shall we say.  The SD40-2 has nothing to be ashamed of, it is one of the most popular and reliable locos of all time and many still are in service, sadly in decreasing numbers.

[oltmannd]

-Modular control system electronics

-HTC trucks

-Longer frame

-No 2nd electrical cabinet in the long hood

Those are the biggies.

Nearly concurrent with the start of Dash 2 production was the introduction of the "clean cab" which had a std. control stand (GE and EMD used the same design) with rounded corners and some other features such as number board lights accessible from the outside instead of the inside, to limit injuries in the cab.

[WSOR 3801]

The number board lights seem to be accessed from inside the cab until 1975-76 or so.  I run a number of SD40-2s with the two doors to get to the lights.  Less air inflitration on the newer design.

The Dash-2s have bigger gauges for the air, and the ammeter.  The Dash-2 ammeter goes clockwise in power, and counter-clockwise in dynamic.  Most Dash-2s have two levers, one for power, one for dynamic. 

Wheel handbrakes on the newer ones, about 1977 or so.  This is a 1980 model, with Q-fans and silencer exhaust stack (not all that effective on this one).

Longer noses about this time as well, and a stairway down inside.

Older ones had a floor height door, then inside the low nose the floor drops.

 

[Compressor man]

Thanks guys, this is exactly the information that I was looking for.

Chris

[wabash1]

The number board lights seem to be accessed from inside the cab until 1975-76 or so.  I run a number of SD40-2s with the two doors to get to the lights.  Less air inflitration on the newer design.

The Dash-2s have bigger gauges for the air, and the ammeter.  The Dash-2 ammeter goes clockwise in power, and counter-clockwise in dynamic.  Most Dash-2s have two levers, one for power, one for dynamic. 

Wheel handbrakes on the newer ones, about 1977 or so.  This is a 1980 model, with Q-fans and silencer exhaust stack (not all that effective on this one).

Longer noses about this time as well, and a stairway down inside.

Older ones had a floor height door, then inside the low nose the floor drops.

 

and on the dash 2 they took the training wheels off also..........unless they was con-rail then they left them on.

[broadythecableguy]

Weren't alot of sd40's rebuilt to sd40-2 specs?

 Scott R. Conforto

[ArtOfRuin]

Yes, but unless you knew it was rebuilt to SD40-2 standards beforehand, it's impossible to tell the difference. Most SD40 to SD40-2 rebuilds look exactly like SD40s.