Compare/Ford 3900 vs Ford 631

Ford 3900 vs Ford 631

Verdict: Ford 3900 vs Ford 631

The Ford 3900 and the Ford 631 are both tractors — here is how they stack up on the figures that matter. Ford 631 leads on rated power with 48 hp against 47 hp. Ford 631 is the lighter machine (1,506 kg vs 2,161 kg), which helps on soft ground and transport, while the heavier model carries more ballast for traction-limited draft work. Ford 3900 is the newer design (1975 vs 1957). In short: choose the Ford 631 for outright pulling power, or the Ford 3900 if a tighter budget and lighter footprint matter more. Compare the full spec tables below before booking a demo.

Tune the fit score

Tell us about your operation

Acreage600 acBudgetMain crop / use

Fit & specs

Ford

Fit score

Best match

Clear

Ford

Fit score

Best match

Clear

Rated power

47 hp

48 hp

Confidence

40%

Guide price

—

Overview

Manufacturer

FordReference

liquid-cooledReference

The 12-speed adds a mechanical over/under to the basic four-speed transmission.Reference

Differential lock

mechanical rearReference

—

Steering

—

power assist optionalReference

Engine

Fuel tank

49.2 LReference

—

Engine (gross)

35.0 kWReference

36.1 kWReference

Displacement

2.9 LReference

2.4 LReference

Bore/Stroke

107 x 107 mmReference

90 x 91 mmReference

Power (gross)

35.0 kWReference

31.8 kWReference

Fuel system

indirect injectionReference

—

Air cleaner

dryReference

oil bathReference

Compression

16.3:1Reference

16.8:1Reference

Rated RPM

2000Reference

2200Reference

Torque

179.5 NmReference

171.9 NmReference

Torque RPM

1200Reference

1600Reference

Starter

electricReference

—

Starter volts

12Reference

Oil capacity

13.0 LReference

5.7 LReference

Coolant capacity

10.0 LReference

14.2 LReference

Belt (claimed)

—

23.9 kWReference

Plows

—

2Reference

Emissions

—

Tier 0Reference

Firing order

—

1-2-4-3Reference

Sparkplug

—

14MMReference

Sparkplug gap

—

0.711 mmReference

Oil change

—

100 hReference

Transmission

Type

gearReference

unsynchronized gearReference

Gears

8 forward and 2 reverseReference

12 forward and 3 reverseReference

Clutch

280mm dry discReference

dry discReference

Oil type

—

SAE 80 Mild EPReference

PTO & Hydraulics

Rear Type

IReference

Control

position and draft controlReference

Rear lift

1549 kgReference

567 kgReference

Rear PTO

independentReference

—

Rear PTO Type

540 (1.375)Reference

—

Engine RPM

540@1800Reference

—

Hydraulic system

—

7.6 LReference

Capacity

—

7.6 LReference

Total flow

—

15.1 lpmReference

Dimensions

Wheelbase

197 cmReference

—

Weight

2161 kgReference

1506 kgReference

Front tire

6.00x19Reference

5.50-16Reference

Rear tire

12.4/11x36Reference

10-28Reference

Standard tires (ag)

Front: 6.00x19. Rear: 12.4/11x36Reference

—

Length

342 cmReference

—

Width

185 cmReference

—

Height (ROPS)

230 cmReference

—

Ag front

—

5.50-16Reference

Ag rear

—

11-28Reference

Rear tread

—

121 to 193 cmReference

Electrical

Charging system

alternatorReference

generatorReference

Charging amps

28Reference

20Reference

Battery volts

12Reference

12 (diesel)Reference

Battery AH

128Reference

135 (12V)Reference

Ground

—

negative (12V)Reference

Variants

611

—

Select-O-Speed, no PTOReference

621

—

Four-speed, no PTO or 3-pointReference

631

—

Four-speed, no PTOReference

641

—

Four-speedReference

651

—

Five-speedReference

661

—

Five-speed, live PTOReference

671

—

Select-O-SpeedReference

681

—

Select-O-Speed, dual-speed PTOReference

Capacities

Fuel

—

49.2 LReference

Rear axle

—

7.6 LReference

631 Serial Number Location

631 Serial Numbers

1957

—

1001Reference

1958

—

11977Reference

1959

—

58312Reference

1960

—

105943Reference

1961

—

131427Reference

1962

—

155531Reference

Fit score weighs budget, operation size, crop match and data confidence against the details above. It’s guidance, not advice — always confirm with a dealer demo.