Crown Race Gears / Ultra4 Racing Gears

Crown Race Gears for Rock Bouncing

Rock Bouncing Gears

Crown Race Gears are engineered for use in reverse rotation GM 14 Bolt axles.

Rock Bouncing

Rock bouncers are harder on ring and pinion gears than any other application. They regularly push well over 700hp on 1 ton axles and 42" sticky tires, running up the most extreme hill climbs they can find at wide-open throttle. As their name implies, rock bouncers often get hung up on obstacles where they use heavy throttle and wheel speed to find traction and bounce their way up the hill.

Each time their massive tires impact a rock or obstacle, the drivetrain and axles bind up as they apply torque to the tires. When the tires get over the obstacle or drop off the other side, the drivetrain temporarily unloads before binding up again when the tires regain traction. While these impacts are relatively mild under normal vehicles, rock bouncers have large tires and high horsepower that allow for very fast wheel speeds resulting in extremely high shock loads when they ultimately hook up and gain traction. These shock loads cause the ring and pinion gear teeth to flex and if they are not engineered for toughness, micro-fractures will begin to form and eventually grow to become cracks and lead to gear failure.

Crown Race Gears are designed, engineered, and treated to withstand the abuses of rock bouncing by starting with a steel alloy that is heat treated and then cryogenically treated to be as tough (flexible) as possible to absorb shock loads, yet have a very hard case (surface) to ensure a very long wear life. This ideal gear case hardness transition is difficult to achieve, yet it is the key to making a ring and pinion set hold up to years of rock bouncing.

Because micro-fractures are the main cause of gear failure in hardcore off-road use, Crown Race Gears go through two separate shot peening sessions that increase the gear density in those critical areas. This process has shown to improve the usable life of gears by about 75%, and has become a standard requirement for most aerospace components.

In addition to heat treatment and shot peening, Crown Race Gears are cut using 5-cut helical gear geometry that uses a sliding motion to transfer power through the gears instead of a pushing force that stays at the center of the ring gear teeth where it increases the likelihood of pitting and micro-fracturing. Then, to take full advantage of the 5-cut gear geometry, Crown Race Gears are REM ISF finished for an aerospace grade smooth surface that, when used with full-synthetic gear lube, reduces friction and power loss by almost 40%.

By maximizing gear toughness, creating a desirable case hardness transition, shot peening the tooth roots, and using an aerospace gear finish, Crown Race Gears are stronger, tougher, and more efficient than any other off-road racing gears available today, making them the top choice of rock bouncers.

Crown Race Gear Specs

Rock Bouncing Gears

  • Heat treated for toughness to absorb shock loads.
  • Two stage shot peened for micro-fracture prevention.
  • Cryogenically treated for improved toughness and durability.
  • Ideal case hardness transition for maximum life.
  • 5-cut gear geometry to prevent tooth pitting.
  • REM-ISF finished for reduced friction and heat.
  • 5-year renewable race warranty.

Rock Bouncer Gear Options

  • Readily available for Dana 60, and GM 14 Bolt axles.
  • Shaved gears available for shaved GM 14 Bolt axles.
  • Designed for use in reverse rotation GM 14 Bolt axles.
  • Ring gear backside REM ISF finished for use with load bolts.
  • Rockwell 2.5 Ton gears available by special order.