This is a High Speed Ring & Pinion Differential Gear Set for 1955-1963 Chevrolet 1/2 ton trucks. NOTE: In 1955, used on both 1st & 2nd Series. Gear sets are a direct replacement for your original differential gears. These gears will give a 3.38:1 gear ratio to install into the original stock differential housing. A 3.38:1 ratio will give your truck the ability to cruise at freeway speeds without major modifications to the drive train of the vehicle. The pinion gear has 13 teeth and the ring gear has 44 teeth. Replaces GM# 3747808, 3697702, 3740874, 3740897 Also available is a gear installation kit, which is sold separately. Specific Applications: 1955-1959 1/2 Ton Trucks (except Overdrive or Positraction); 1957-1959 1/2 Ton 4WD Front Axle; 1960-1962 1/2 Ton - Series 10; 1963 1/2 Ton - Series 10 4WD This part is oversize and special freight charges will apply. Call or email us for a freight quote.