NSX Shift Fork Restoration

Nowadays it’s getting harder and harder to find parts for classic JDM cars.  Recently we had an Acura NSX in the MotoIQ Garage to repair its transaxle.  The synchros, hubs, hub sliders, and some shift forks were worn out and much to our dismay, we found that some of the shift forks were no longer available as repair parts.  Here is how we went about repairing a well-worn fork.

The first thing we did was to tig-braze some silicon bronze material onto the ends of the forks.  Tig brazing is using the torch of the tig welder to melt a silicon bronze filler rod onto the surface.  Since a tig torch heats the base metal to a much higher temperature than a traditional brazing torch, some of the base metal melts and intermingles with the bronze, forming a really strong bond where the steel and bronze come together. You can see the intermingling here in this picture.

Here is a close-up of the intermingling. The steel bronze aggregate has a good combination of hardness with the bronze providing lubricity and sliding wear resistance.  Using a mill we got the tips of the shift fork roughly into shape, then hand-fitted the tips to the transmission hub sleeve with a stone to the tight end of factory tolerance.

After the fitting we WPC treated the fork to give the tips some more surface hardness and additional lubricity.