Project NSX: Part 1 – Building the Bulletproof Transaxle

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Here Billy Johnson polishes the gear teeth on this bench grinder with a scotchbrite green wheel.  You don't want to polish things down to nubs, just enough to break the sharp edges.

Since the NSX has a decent transaxle we did not opt for the full court press drastic treatment that we might give a Nissan FWD unit but something that would make a big difference in durability giving the most bang for the effort.  The weak point in the NSX transaxle is the gears so we treated them to a deburring and tooth polishing.  Using a scotchbrite green wheel on a bench grinder, we polished the sides and tops of the gear teeth to eliminate sharp edges and crack inducing stress risers.  Polishing also helps prevent the gears from digging into each other which also greatly weakens the teeth.

After polishing, no more sharp edges and machine marks.  Just nice and smooth.

We also WPC treated all of the gears and shafts of the transaxle including the ring and pinion gear.  WPC is the Japanese wonder metal treatment that in simplistic terms microforges the surface of the material making it stronger, much more fatigue resistant and with its silky smooth surface finish, reduces friction and heat.  WPC treatment in short makes the gears have about double the life in high stress situations and in a transaxle like the NSX, reduces about 5 whp worth of friction.

On the left is the finished product, deburred, polished and WPC treated vs the sharp and rough stock part on the right

We also replaced the gear hub sliders, balk rings and syncros of the transaxle with brand new genuine Acura replacement parts and WPC treated them.  The smoothness of the WPC surface will help make for easy and fast shifting and the increase in surface hardness means longer life for these highly stressed parts.  The WPC micro pitting means that the syncros will have good grip to help speed shifts while retaining lubricant on the surface and the increase in surface hardness ensures a long life at the same time.  The smoothness of WPC surface on the outer parts of the syncros means smooth shifting due to reduced friction between the syncro, hub slider and balk ring. Our transaxle will be reassembled with new seals and with an OS GIken LSD. 

The stock ring and pinion is on the left compared to the OS Giken part on the right.  Both gears are polished, deburred and WPC treated.  We choose to stick with the stock 4.06 final drive gear ratio.

To increase the strength of the transaxle case, we removed the stress risers by grinding off all of the sharp flashing made during the casting of the housing.  Smoothening this not only strengthens the housing, but makes it a lot nicer to handle for re-installation.

Once all of the gears are treated and together, the transaxle goes back together and is ready to be installed.

Sources

M-Workz Motorsports Consulting

OS Giken

WPC Treatment

FX Motorsports Development