70:1 Metal Gearmotor 37Dx70L mm 24V with 64 CPR Encoder (Helical Pinion)

via Pololu
$101.41
SKU PL-4694

This gearmotor is a powerful 24V brushed DC motor with a 70:1 metal gearbox and an integrated quadrature encoder that provides a resolution of 64 counts per revolution of the motor shaft, which corresponds to 4480 counts per revolution of the gearbox’s output shaft. The gearbox is composed mainly of spur gears, but it features helical gears for the first stage for reduced noise and improved efficiency. These units have a 16 mm-long, 6 mm-diameter D-shaped output shaft. This gearmotor is also available without an encoder.

For full details see - Pololu