Some say we over engineered the GDM500/650 – but we wanted to provide the most advanced technology and product to our customers. With an upgraded, powerful gearbox design that was engineered just three years ago, you can be sure this gearbox will handle the next twenty years of drilling demands. Available in two different A/C drilling motors as well as a DC motor, the GDM500/650 offers many different power options. The main shaft is cut to 7 5/8 inches and can be re-threaded up to three times. This unit creates the most torque in its class.

Like our other Models, the GDM500/650 comes standard with our built-in predictive and preventative maintenance software that teaches rig crews to get the most out of your investment.

Source:- http://www.globaldrillingsupport.com/gdm-500650/

Global Drilling Support