TRF421X Tensioner Nut for 42391 - Tamiya 9803478  [9803478]

Precision tensioner nut for TRF421X

This replacement tensioner nut is a purpose-built RC part made to fit the 42391 TRF421X assembly. It performs a basic mechanical task: set and retain the tension where the original nut sits, enabling repeatable adjustments during setup and servicing.

On the model it helps you fine-tune drivetrain belt or linkage tension and keep consistent clearance in the affected area. As a direct replacement-style component, confirm alignment and mounting against the 42391 TRF421X points before completing assembly.

Fitment is simple: place the nut onto the specified threaded interface, turn to reach the desired tension or gap, and check that the drivetrain or linkage moves smoothly through its travel. After setting, recheck alignment and rotational tension to ensure the adjustment stays secure.