The Ferrari 355 has suffered a particular problem for quite some time and there was really no explanation on what was causing this problem, only speculation. We had been asked on several occasions to re-manufacture Quill shaft part number 162909 due to owners having breakage problems. One customer of ours had called us to explain that they had broken 3 x OEM shafts in succession and was desperate to find a solution. It was approximately 2 years of research and development that followed in unearthing problems found and designing & testing improved parts.
Cutting a very long story short the quill shaft from the factory has too much clearance for a shaft that has to suffer immense reciprocating forces dues to acceleration / de-acceleration. These clearances have been addressed with the Hill parts making the spline a much closer fit. One of the other problems is that the the splined flywheel hub has a tendency of wearing " bell mouthed" which then causes the quill shaft to bend in its rotation thus causing micro cracks in the root corners of the triple seal grooves. (This of course is happening well before the quill shaft breaks!)
We have managed to address a number of issues in this project.
1 - Creating a new quill shaft utilising an aircraft release specification material that has an ultimate tensile strength of over 45% of the original OEM part and at the same time offering much more torsional flexibility.
2 - Designing a tool that can be easily used by workshops to check the wear in the female splines.
3 - Manufacturing a replacement splined flywheel hub with much closer tolerance spline over the OEM part.
Video of Hill Spline Gauge H01-03600 checking a worn OEM Flywheel spline. (Click on the right arrow in the video below to view the recording of the Spline Gauge being used to check a good spline.)
Notice at the end of the video we show down the bore of the spline and there is no obvious visual tell-tale signs that shows how badly worn the spline is.