The Making It Work

  1. In PART 1 we CAD’d, analysed and engineered the Z33 6 speed gearbox conversion and manufactured a whole bunch of stuff to adapt the gearbox onto the SR20DET.
  2. In PART 2 we shoehorned the Z33 box into the Silvia.
  3. Now in the final PART 3 it’s the rest of it, the stuff needed to make it work like normal…


Shifter and It’s Position

With the remote shifter linkage cut and welded as short as possible this is how the shifter will sit:


I don’t mind the shifter feel of a shortened linkage, and many of our customers are happy with it in the Z32GCK that we sell, but there are a few people that have tried it and don’t like it. They would rather cut the car even more – further back or further forward in the case of an RB25 gearbox conversion and use a dogleg shifter instead. That’s not my cup of tea. Horses for courses?

Either way is not perfect so choose your poison. 2018 update: Actually… Alpha Omega has now engineered has something that *is* perfect! The R33 Gearbox Conversion Kit – Factory


Gearbox Cross Member

Probably the easiest part of the conversion but remember we hammered out the cross member mount to fit the gearbox?


Also remember that the gearbox is physically massive? It’s much larger “around” or diameter wise. With the Z33 gearbox lifted as high in the tunnel as possible (read: the gearbox rubbing on the underside of the tunnel) it is still tilted down 9°. That means the front of the engine is tilted up 9°.

Some cutting and welding to the intercooler piping was needed, but at least there was enough slack in the wiring and other hoses to accomodate it.

The diff angle was also adjusted as much as possible but there was not enough “adjustment” available. We came this far so we just ran with it but know that with such a large difference in angle we can expect vibrations in the tailshaft caused by the front VS the rear unijoint speeds.

The thing that can’t be fixed short of making a new tunnel is how low the gearbox hangs out the bottom of the car. It sits significantly below the frame rails. This Silvia is lowered by 35mm, has about a 1-finger gap between guard and tyre and it scrapes the gearbox everywhere it goes.


No Speed Sensor

The Z33 box does not have a speed sensor which means no speedo, and without a speed input into the ECU the ABS can’t function, nor can you do advanced things like anti-lag launch control or speed/gear-based boost control. We were going to implement a hall sensor off a tailshaft driven gear, or you can get a GPS speed reading unit and wire it in, but speedo and ABS aren’t that important because race car.



  1. Custom adapter plate/bellhousing machining/flywheel/clutch kit/throw out carrier and bearing/other stuff had to be made
  2. Entire transmission tunnel needed hammering, front to mid to rear
  3. Exhaust requires hammering, cutting and welding
  4. Gearbox requires grinding in various areas
  5. Engine has to be dropped to fit / remove the gearbox
  6. Shifter position is ugly
  7. No speed sensor = No speedo = No ABS
  8. Vibrations from the tailshaft due to large 9° gearbox angle
  9. Gearbox hangs super low – scrapes everything


Our 2009 plan was to engineer, test and sell the Z33 gearbox conversion kit by 2010. In the end we forced it to “fit” and forced it to “work” but at what cost?

There is much more at stake than just dollars and cents and sense.

A Z33/Z34 350Z/370Z/CD009 6-speed gearbox conversion into a SR20-powered 180SX/240SX/S13/S14/S15 is great in theory, and as an engineering company we loooooooove theory so we put the theory to practice and the results are very clear. Nothing is perfect in this world but Alpha Omega Racing will not provide such highly flawed results to our valued customers.

After all that work, money, customising, bashing, cutting and welding, scraping, noise, heat… we pulled it all out, un-done all everything and you now know exactly why we still manufacture and use the 5-speed gearbox conversion kits “Z32GCK” and “R33GCK-Factory“.

If the 6-speed conversion was better… we’d stop making the 5-speed conversions! That’s the whole idea of doing all this lol.


I hope you enjoyed the read and I wish you all the best that life has to offer!

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