dogbox sti 6 speed? what goes to plan? what doesn't?

hmmm. what happens at 450akw+ when a std 6 speed TY856 won't cut it. Im talking about the actual 6 speed found in STI's not your 5+1 (sorry vb owners!)

You will often see 4th gear either as a gearbox soup or synchros being munched as a cause effect of shifting similar to Dominic Toretto.

Experimenting with the ty856/drag racing / Haltech drag challenge and a couple of machining skills and theory I had picked up over 2024-2026 I decided to create a dogbox to bolt into the casing of the ty856.

the design brief? 9 second pass. A gearbox geared for optimal shits and trap speed.

the base? a DCCD 08+ box. Despite not having the internal oil pump drive off the centre diff, I managed to make oiling guides a little more liberal :)

the car? A red g3 sti hatch from hell. 650AKW. A giant viking rowing gears.

the goal? reliability. Survive drag challenge!

did we achieve it all? yes and no.
9 seconds? done
winning drag challenge? done
did the box survive? yeah nah.


Now hold your horses, the gearset I machined and assembled survived! no failures arising from my work and machining. Trap speed in 4th was 264kph. Excellent for the cuban mile.

So what exactly failed? The very part I told its owner that would break. Fingers and selector. Solution? Iteration #2 with a design revision to increase material and shear strength of the striker.

Material choice: chromoly. FEA on the part called for increased SA and adding more material to overall shape.

Machined within 2 weeks.

Testing wrapped up this week *09/2026* box is healthy and going strong.

lets see how we go at drag challenge 2026!

jperf!