Dash 8 external differences

[diburning]

Are there any external differences between the Dash 8-32B, the Dash 8-39B, and the Dash 8-40B?

[Allen Hazen]

The 39/40 is a bit longer. (Amtrak's passenger B32-8WH, or whatever the official designation is-- the "Pepsi Cans" as they were called in honor of their prize-winning original color scheme-- are, i.i.r.c., built on B40-8 length frames, but with a slightly different spacing of the trucks.) There are differences between SP and Santa Fe B40-8 (things like sand filler placement): I don't know if any of the "ever order slightly revised" design changes can be used as consistent B39-8/B40-8 distinguishers.
The most recent incarnation of the "Diesel Spotter's Guide" series has, I think, exact lengths. The difference between a B32-8 and a B40-8 is something like 3 feet.

[Allen Hazen]

Further details:
"The Contemporary Diesel Spotter's Guide" by Marre and Withers (Withers Publishing 2000: I think there is a new edition since) gives the following lengths and truck center distances:
Pre-Dash-8 types for comparison:
U23/30/33/36B: 60'2"/36'2"
B23/30/36-7, including BQ23-7: 62'2"/36'8" (this is an oversimplification: I think these lengths are good for early production of these models but there were minor changes over their lives)
B30-7A (Missouri Pacific): 62'2"/36'8"
B30-7A1 (Southern): 62'4"/37'10"
B30-7A(B) (Burlington Northern): supposedly 62'2"/36'8"; I don't know whether this applies to both orders or not.

12 Cylinder Dash-8:
B32-8: 63'7"/36'7" (This is good both for the BN-painted 1984 demonstrators and for the 1989 production version)
B32-8WH (Amtrak): 66'4"/39'7.875"

16 Cylinder Dash-8:
B36-8 (GE test unit),B39-8 (Santa Fe-painted demonstrators), B39-8E: 66'4"/39'4"
B40-8, B40-8W: 66'4"/40'1.5"

Most of the length difference between the B32-8 and the B39-8E seems to be in the long hood, so look for hood openings for more differences: the obvious one is the traditional distingushing mark of 12-cylinder vs 16 cylinder GEs: six tall engine compartment doors on each side for the "small" engine, eight for the large. Production B32-8 and B39-8E seem to have the same number of handrail stanchions (at least on the left side), but spaced differently.

[MEC407]

The number of hood doors is the main thing I look for. Somewhat easier than using a tape measure. (Of course, that doesn't help much when trying to distinguish a B39-8E and a Dash 8-40B; that's when you have to start looking for the really small details.)