VO-1000's were built between November 1939 and July 1946.
All were equipped with 1000 HP 8 cyl VO prime movers.
All were designed as yard switchers without MU connections.
Phase 1..November 1939 to May 1941-Circular front fan opening, tall side radiators, Single exhaust stack on left near the cab, high front headlight, 2 uprights on front and rear handrails. Curved sheetmetal at cab steps. Overall length 48'-00".
Phase 2..June 1941 to June 1942-Rectangular pointed front radiator, small side air intake up high, headlight partially countersunk, Single exhaust stack on left near the cab, cab height reduced by six inches, overall length increased 10", to 48'-10". Baldwin trucks dropped(June 42)Commonwealth trucks become standard. 3 uprights on front and rear pilot handrails.
Phase 3-June 1942 to January 1945-Small side air intake moved to top of hood. Headlight has sheet metal added on both sides of fairing. Curved sheetmetal at cab steps is squared off.
Phase 4-January 1945 to June 1945-Single stack on left near cab is changed to two stacks on left side.
Phase 5-July 1945 to July 1946-Two stack arrangement changed to four stack arrangement.