Testarossa / 512TR


As our gallery at the bottom of the page highlights, shafts, gears and differentials were all weak points on these platforms.  Rather than replace an old, failure-prone component with a new, failure-prone component we offer the option of properly engineered replacements that won't fail; shafts designed to twist that won't snap, gears made of modern alloys and treated that won't break and differential housings that won't crack and don't require reusing 30+ year old internals.

After commissioning a complete replacement of his 512TR's internals with our components, one 40-year Ferrari owner commented:  "I have never driven another Ferrari that manually shifts as well, is as quiet or as smooth... absolutely no excuse that a quarter million-dollar super car, that was also Ferrari's flag ship back in its day, should shift so poorly or have the history of gearbox problems the Testarossa and 512TR do.  Now mine doesn't and it's a joy to drive again."

Gearbox Solutions

Limited Slip Differentials


Ferrari P/N's  

106769, 101626, 147258, 190005, 199782, 183932, 238598, 103262, 146769, 148253, 155099 

HCF's LSDs feature a machined housing rather than the failure-prone welded unit many came equipped with (see below).  What sets these differentials apart is they're not just a housing, they are complete units.  They have all new and improved-quality side gears, spider gears and positraction components.  

Propeller Shafts


Ferrari P/N's 

151651, 162909 

The propeller shaft transmits engine power to the transaxle.  In response to many early failures, Ferrari made a stronger shaft which commonly broke the now weaker transmission main shaft - a five figure repair.  The unique steel alloy of this improved shaft is designed to provide a high degree of torsional flex to insulate components like the main shaft from destructive shock loads.

Main shafts / Gears


Ferrari P/N's 

109716, 156925, 183964

Motorsports-derived main shaft and gears manufactured from a aerospace-derived steel alloy.  Main shaft spline count is increased to 32, distributing forces more evenly in the full 360° rotation.  The combination of higher quality materials and spline count eliminates common issues with the OEM components - broken gears and snapped input shafts.

OEM Weak Point


Highlight of where they break in the Testarossa / 512TR.  Often when a differential breaks it's a catastrophic failure and the internal parts are damaged; Ferrari has not offered replacements in some time.  Consider replacing your failure-prone OEM unit during your next major service.

OEM Weak Point


The problematic, failure-prone early shafts generally fail where the red arrow indicates.  This propeller shaft was designed as a replacement for both a broken early shaft and also for a functional late shaft - ideally before damaging the much more expensive main shaft.  See photo gallery for main shaft failure.

OEM Weak Point


Noticeable tooth wear on this 20k mile first gear along with a complete failure starting at the machined groove.  See gallery for an example of both a twisted main shaft and a broken main shaft - both the result of a stronger propeller shaft.

Kevlar Composite Clutch Solution

Kevlar disc clutch assemblies and flywheels - in stock


Upgrading to HCF's Kelvar composite clutch assembly has two primary benefits over the OEM assembly.  First, there is a noticeable improvement in pedal effort that customers report makes the car more enjoyable to drive.  Secondly, the wear characteristics of this particular kevlar composite are 1/2 to 1/5 that of traditional OEM facings.  Lightweight flywheel available on request. 

Fits:  512TR, F512M, 456, 550, 575, 612 

Complete assembly with pressure plate


Pressure plates rebuilt and customized to work with kevlar material.  For proper results, the kevlar disc must be paired with one of our customized pressure plates.

Kevlar composite disc


Made in the USA of a patented textile kevlar composite material, these kevlar discs outperforms other kevlar facings in terms of disc wear, engagement, chatter and flywheel abrasiveness.

Kevlar Disc Real World Example


512TR / 550 Maranello Kevlar Composite Clutch Disc

Rebuilt OEM disc with segmented facings.  As installed during engine-out service in 2011. 


1 year later - disc condition

A little over a year later the gearbox was damaged and developed an oil leak, necessitating a tear down.  Clutch disc showed virtually no wear and, as this particular Kevlar fiber composite material is designed to work wet or dry, it did not need to be replaced due to oil contamination. 


6 years later - disc condition

In 2017 the gearbox main shaft broke, giving the opportunity to inspect the clutch components.  No more than 0.5mm of measured wear. 

Other Model-Specific Products