Upper Deck for TRF421X (part 3404174) compatible with 42391 - Tamiya  [3404174]

What this upper deck does for TRF421X

This upper deck is offered as a spare with reference code 42391 for the TRF421X chassis line. Positioned as the upper mainplate, it is intended for repair use or for drivers who swap decks to fine-tune chassis flex and balance as part of their setup routine.

The profile and mounting holes are made to coincide with the TRF421X original layout, allowing fitment with existing standoffs and fasteners without chassis alteration. When installing, double-check hole alignment and screw length to preserve chassis geometry and avoid unintended play or binding.

Functioning as both a spare and a tuning option, the deck plays a structural role: different deck pieces change fore/aft flex behaviour and can be used to tune traction and steering feel for varying track conditions. Keep removed fasteners and shims together to maintain consistent setup when reverting.

Compatibility notes

Compatible with 42391 TRF421X as shown by the part code and product description.

Suitable for racers and mechanics who require a direct replacement or who trial deck stiffness changes; fits the TRF421X without modification.