Behemoth Helix IL Inline EV Gearbox – 2.72:1 Planetary, 13,000 RPM

The Behemoth Drivetrain Helix IL is a single-speed inline reduction gearbox built for high-RPM electric motors. It bolts between the motor and the driveshaft, so you keep the vehicle's existing rear axle, differential and driveline layout: no clutch, no shifting, and no new axle.

Inside is a custom high-speed planetary gearset with a 2.72:1 reduction, hybrid ceramic bearings and pressurized oiling. Behemoth has tested it at motor input speeds up to 13,000 rpm.

The price includes a complete cooling system: a Derale 13750 Atomic-Cool remote fluid cooler with its own 8-inch electric fan, and a MARCO UP2/OIL 12 V electric oil pump (16422012). You also get an electronic parking pawl, park position sensors and a temperature sensor.

The output takes a 32-spline TH400-style slip yoke, so driveshaft parts are off-the-shelf.

Compatible with Cascadia, Turntide, HyPer 9 and YASA motor platforms (per Behemoth), including the Cascadia SS-250 and Turntide AF300/AF400 motors we sell.

Notes from the Current EV team

Everything we sell is a part we use in our own builds. The Helix IL is one of our favorites: the 2.72:1 ratio is right for most cars with a typical rear axle, it's the quietest gearbox we've ever used, it runs cool even when we work it hard, and the electronically integrated parking pawl is a huge upgrade over rigging up a separate parking brake. It also comes with its own radiator and pump, which none of the other gearboxes we've used do.

Working out your gearing

The 2.72:1 reduction multiplies with your axle ratio. With a 3.73 axle the overall ratio is about 10.15:1. On a 27-inch tire that's roughly 79 mph at 10,000 motor rpm and about 103 mph at 13,000 rpm. Send us your axle ratio, tire size and motor and we'll run the numbers.

Specifications

What's included

• Helix IL 2.72:1 inline gearbox
• Derale 13750 Atomic-Cool remote fluid cooler with built-in 8 in fan
• MARCO UP2/OIL 12 V electric oil pump (16422012)
• Electronic parking mechanism
• Park position sensors
• Temperature sensor

Is it right for your build?

The Helix IL suits conversions that keep a solid rear axle, transfer-case 4x4 drivelines, motorsport and prototype builds. For independent suspension with an integrated differential, see the Behemoth Helix E30 and E40.

Typical lead time is 6–8 weeks. Ships by pallet freight, quoted separately. Contact our engineers to confirm fitment with your motor and driveshaft.