Yes, after all these years we still haven’t really figured them out completely.
To summarize…
We are talking about two different wedges.
C.3829 is the thick tapered aluminum wedge pictured in Urs Schmid Vol. 1 pg 119.
He shows an early ENV axle on which it appears that the spring saddle is very close to the axle tube.
Here is my later ENV axle, and you can see there is some clearance, the saddle is taller. This may explain why the thick wedge is not used on my car.
C.3186 is the thin fiber wedge listed only in the 140 and 150 SPCs and without explanation in the Service Manuals.
Curious that it has such a low part number, in proximity to a lot of Mark V chassis parts, suggesting it was designed about the same time. But it does not seem to have been used on Mark V, not listed in the SPC anyway.
Makes you wonder if it was a service part used on an “as needed” basis, like for adjusting caster angle and diff nose angle on individual cars.
Perhaps we are making an invalid assumption in thinking they were on every single 140 and 150?
We discussed them in 2014.