Truck centers are the dimension from center to center of truck bolster, not the jacking pads.
This data is for units as delivered from the manufacturers.
Always refer to pictures of the unit to be modeled as many trucks are interchangeable.
The trucks were sometimes swapped by the Railroads or rebuilders.GENERAL ELECTRIC LOCOMOTIVE WORKS
TRK CTRS TYPE "B" WHB MODEL 36'-02" FB2 9'-00" B23-7 36-08 AAR "B" & FB2 B30-7 37-02 FB2 9'-00" B36-7 39-00 FB2 9'-00" B30-8,B36-8,B39-8 40-11 FB3 13'-07" C30-7,C36-7 30-08 FB2 9'-04" U18B 38-04 FB3 13'-07" U23C 38-04 note 6 13'-00" U25C, U28C 41-11 FB3 13'-07" U28C,U30C,U33C,U34CH,U36C 41-02 FB3 13'-07" U28CG 41-06 note 7 U50 50-02 note 8 U50C 36-02 note 9 UD18,U23B,U25B,U28B,U30B,U33B,U36B,B30-7 NOTES for GE trucks:
6: U25C & Early U28c used a special tri-mount with deep side frames.
7: U50 used a pair of AAR "B" trucks mounted on a span bolster front and rear. truck centers are span bolster to span bolster.
8: U50c used the trade-in 6 axle trucks from their gas turbines.
9: Most "U" boats used AAR "B" trucks and option was the FB2(Floating Bolster 2 axle)whb of 9'-00".
AAR type "B" trucks used on road units have a whb of 9'-04" with GE traction motors and 9'-10" with Westinghouse motors.
FB3(Floating Bolster 3 axle)is a GE version similar in appearance to the EMD "flexicoil", two versions were used, the "Adirondack" and the GSC version both have a whb of 13'-07".GE's 2 & 3 AXLE TRUCKS EXPLAINED with PICTURES More GE Information © S.A. McCall