SD40T-2 Top View

SD40T-2 Top view

As of December 1991

This top view of an unidentified tunnel motor was taken in December 1991. It's the trailing unit on the swing helper of a unit coal train. Judging by the horns, it's either from the group 5398 - 5413, or the Nathan horn has been replaced (which seems to have happened a few times). There's a bit of motion blur on the near end, but most details are discernable despite that.

Rio Grande's SD40T-2s came in several groups, as shown in this table.

Number Range	Date Purchased	Comments
5341 - 5355	Oct 1974	"Short" (81-inch) nose. (All SD40T-2s were delivered in the billboard "Rio Grande" scheme.)
5356 - 5366	July 1975	"Short" nose
5367 - 5373	Aug 1975	"Short" nose
5374 - 5385	Jan 1977	"Long" (88-inch) nose
5386 - 5397	Aug 1978	"Long" nose. Low-nose light mounted in external box.
5398 - 5413	Mar 1980	"Long" nose. Leslie horns.

Specific information for individual units may be found on the Rio Grande Modeling & Historical Society's SD40T-2 page.

(1) Class lights on rear corners.

(2) Radiator intake grilles. From ground level, one may see through the other side. The fans are mounted internally above this compartment, forcing air upward through--

(3) -- the radiator grilles.

(4) Grab iron above radiator on left side.

(5) Traction motor blower duct.

(6) PTC control cabinet.

(7) Leslie P3 horn. The bells are larger and longer than the Nathan version.

(8) Antennae: Sinclair, mounted just to left of centerline, and small whip antenna to the right.

(9) Dynamic brake fans.

(10) Engine room roof vent.

Comments:

The deck-level radiator intakes and the panel grilles on the roof make the tunnel motor series instantly identifiable.
The Positive Traction Control system was installed on Rio Grande SD40T-2s beginning in 1985. This system controlled wheel slippage, giving the locomotives better footing on the rail and hence a higher tonnage rating.
Nos. 5398-5413 were delivered with the larger Leslie horns. Possibly a few older units received them before SP modifications.
The whip antenna was added sometime after delivery.
All Rio Grande hood units came with dynamic brakes. The larger SD series (6 axles) dynamic brakes have two fans, as opposed to the single fan on the GP series.

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