For any front engine Syncro, with a free wheel, sooner or later, the rear differential actuator, for the reverse gear, will need a grommet, (009 525 642 vw part number), replacement.
But, counting from the year 2013, it is dropped without replacement by vw.
So, in this video, we can see a D.I.Y. 4 ply teflon, plumber's tape, with the same special technique I am using for the teflon belts manufacturing, how nicely can replace the original, having a much longer life expectancy.
The operating pressure of the system is such that any material is under heavy load. The material itself, as well as, the joins, must be both, elastic and sturdy.
The 4ply teflon is a first attempt for a light and flexible structure. It seems as if this is the lower limit, anything less it seems that will not afford the pressure.
(Syncrovention).
The Syncro Heresy