Quick Answer

Most Redcat gearbox problems come from worn hinge pins, loose servo mounts, or damaged differential gears. Start by inspecting the suspension linkage and servo mount before opening the gearbox. Many drivetrain noises are actually from loose parts, not internal gear damage.

Grinding or Clicking Noise from the Gearbox

A grinding or clicking sound during acceleration often points to worn differential gears or a misaligned gear mesh. Check the gearbox for debris or stripped teeth. If the gears look intact, the issue may be a loose upper servo mount that lets the servo shift under load, causing the drivetrain to bind.

Gear Slipping or Loss of Drive

If your Redcat loses power to the wheels but the motor spins, the differential gear set may be stripped. The RER13520 Differential Gear Set is a direct replacement for Caprice Classic, MONTE CARLO, SixtyFive, SixtyFour, and SixtyThree models. Before replacing, confirm the gearbox housing isn't cracked and the hinge pins aren't bent—bent pins can cause misalignment that mimics gear failure.

Binding or Stiff Drivetrain

A drivetrain that feels stiff or jerky when rolling by hand often has a bent suspension arm hinge pin or a misaligned servo mount. The 50038 lower inner suspension arm hinge pins (6 x 94 mm) are a common wear item on Rampage MT and legacy Rampage Dunerunner models. If the pins are straight, check the RER14761 Upper Servo Mount Front—a cracked or loose mount can cause the servo to bind against the gearbox.

Diagnosis Steps for Redcat Gearbox Problems

  • Symptom: Grinding or clicking noise during acceleration or deceleration. Noise is often from loose external parts, not internal gears.
  • Likely Cause: Bent hinge pins (50038), loose servo mount (RER14761), or stripped differential gears (RER13520). Check pins and mount before opening the gearbox.
  • Corrective Action: Replace bent hinge pins or cracked servo mount. If noise persists, inspect differential gears for damage and replace if needed. Replace parts in order of cost and accessibility.
  • Stop or Choose Another Option: If the gearbox housing is cracked or gears are stripped beyond the differential set, consider a full gearbox replacement instead of piecemeal repairs. When housing damage is found, stop and evaluate replacement cost.

Parts That Help Diagnose and Fix Gearbox Issues

  • 50038: These Redcat Racing lower inner suspension arm hinge pins are replacement pins for the suspension linkage. Each package includes 4 pins, with each pin measuring 6 x 94 mm. Fits Rampage MT and legacy Rampage Dunerunner models. Bent or worn hinge pins can cause drivetrain binding that sounds like a gearbox problem. Replacing them is a quick, low-cost first step before opening the gearbox.
  • RER13520: The Redcat Racing RER13520 Differential Gear Set is a replacement part supplied as a one-set package. It is listed for use with Caprice Classic, MONTE CARLO, SixtyFive, SixtyFour, and SixtyThree models. If you confirm the differential gears are stripped, this set provides a direct OEM replacement. Always inspect the housing and hinge pins first to avoid replacing gears that will immediately fail again.
  • RER14761: Redcat Racing RER14761 is an upper servo mount front spare part, supplied as a single piece. It is listed for use with the MONTE CARLO current vehicle. A loose or cracked upper servo mount can cause the servo to shift under load, creating gearbox-like noises and binding. Replacing it costs under $5 and may resolve the issue without touching the gears.