Western Railroad Discussion > question about SD40/40-2s

What are the physical differences on an SD40 and a 40-2? How can you tell them apart?

Posted from Android

Biggest difference is that all of the SD40s had Flexicoil trucks, while ALMOST all of the -2s had HTCs.
The -2s had an oval radiator sight glass in the door so you didn't have to open it to check the water.
The -2 radiator louvers were different, and protruded out slightly from the hood.
I am sure there are othrs...
G

SD40-2 is a slightly longer locomotive, with a bigger "porch" on the rear (actually, both ends, I believe). They were built on the SD45-2 frame...

 

I thought the radiator louvers change was a few years into the SD40-2 production.

It was. Both started with chicken wire then the -2 went with corrugated mid 70s

I've found the fastest way to tell the difference is this order:    1)   Rear radiator fans (protruding vs. flush).   2)  Trucks.   3)   Length/porches.      1 and 2 can be a bit misleading as early SD40-2's had the flatter SD40 radiator fans, and many railroads (like Conrail) didn't use the typical SD40-2 trucks.   So sometimes you have to check all three features or memorize the roadnames and roadnumners to figure it out.    Conrail was the tricky one in my book.   UP, BN, and ATSF were more cut and dry.

"Chicken wire" radiator grills were last seen on SD18/24 locomotives.

SD40/40-2 diesels had standard height fans as the default fan. Lower or flush fans were a railroad specified option. Later SD40-2s had Q fans which had a raised top cover.

Diesel Spotters Guides are your friends.

 fbe Wrote:

> "Chicken wire" radiator grills were last seen on
> SD18/24 locomotives.

I think what they mean by "chicken wire" is the type seen in these photos of MRL SD40 #351 and MP SD40-2 #3101, where the outermost component on the radiator intake was a flat, square mesh of wire:

http://www.trainorders.com/discussion/read.php?3,2492205,2492876#2492876
http://www.trainorders.com/discussion/read.php?11,2808406

The "corrugated" type had a very fine mesh stamped into a washboard pattern as the outermost compenent as on ICE SD40-2 #6418:

http://www.trainorders.com/discussion/read.php?3,3391478,3392888#3392888

The third shot in this thread shows the difference to good effect:

http://www.trainorders.com/discussion/read.php?1,3774909

Now...can someone explain to me what constitutes a "flush" versus a "protruding" EMD fan?  The only SD40-anything I know of where fan shrouds don't protrude above the top of the hood are SD40T-2's, because the fans sit below the radiator cores instead of above them.

Evan,

While the grill on the MRL 251 is a 2 piece grill consisting of a stamped grill overlaid by rods welded into a square pattern that is not what is commonly known as a chicken wire grill which was a woven wire screen found on EMD F, GP, SD and SW locomotives from the 3, 7 and 9 series.

Some eastern railroads with low overhead clearances, EL for one, had fans which had a cap which was lower than standard. I also think the mount was such it sat beneath the roof top rather than above it. These fans do seem interchangeable as you can find photos of EL and Conrail locomotives with both heights of fans on the same unit. This has nothing to do as to whether the unit is a 40 or 40-2 model. For tunnel motors the fans were mounted underneath the radiator cores not above them.

Posted from iPhone

There's a lot of good information here, but note that the coolong water level "sight glass" is not a reilable spotting feature between pre- and post Dash-2 production.  Prior to the Dash-2 line, it was at least an option, and many SD40s (including SPs last order of 10) were biult with the sight glass.  Another feature not mentioned is the overhang of the rear cab roof.  On all non Dash-2 EMD hood units (the SD45X was essentially a Dash-2), the rear of the cab roof is flust with the back wall of the cab.

Elizabeth

The generator room door on 40-2 is different, has a single handle, you can slide to open. SD40 had two clamshell pieces with wing nuts holding them down. 40-2 also has a step down inside the short hood. 

Further confusing matters, of course, is that CSX (and possibly others) rebuilt SD40s with -2 electrical systems and called the results SD40-2s.

I seem to remember the older SD40's had the brake wheel located on the rear end of the long hood -mounted on a brake wheel stand on the 'back porch'. SD40-2's at my railroad and the U.P. all had their hand brakes located on the short hood on the fireman's side.

Posted from iPhone

Not all SD40s had a rear platform hand brake wheel. Some later units had the handbrake ratchet set into a recess in the left side of the nose.



Edited 1 time(s). Last edit at 07/25/16 19:38 by fbe.

fbe Wrote:
-------------------------------------------------------
> Not all SD40s had a rear platform hand brake
> wheel. Some later units had the handbrake ratchet
> set into a recess in the left side of the nose.

Even worse, some early SD40s (like Santa Fe's 1966 units) also had the handbrake in the nose.

Nathan Beauheim
Cheyenne, WY