4 speed/Underdrive DIY
4 speed/Underdrive DIY
4 speed/Underdrive DIY

4 speed/Underdrive DIY

Regular price $1,099.99
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Machined from a billet of 6061-T651 with a fully integrated 8620 hardened steel shaft, this underdrive box will bolt up to either our D300 or NP205 Rock Box.

We have done away with the traditional style of shifting where the shift collar is rotated, instead the shift collar in our box moves parallel with the shaft allowing for smoother engagement and an underdrive that doesn't pop out of gear.

Parts required to complete from either a 231 or 241

Planetary Assembly 
Input Shaft Bearing 
Shift Range collar 

100% made in the USA