More tips and tricks:
Shortening a drive shaft :W123 and W114/115
step one :
– The new drive 722.6 shaft needs to be about one inch shorter than the original one
– Take one drive shaft from a “modern” 722.6 car .
– The spline side will fit to the 123 shaft but the shaft will be to long .
– Shortening :
– Make a marking along the full length before cutting out the part you want to shorten.
– Be sure that you make a straight cut
– look /make a inside liner bush about four inch long ( some say an outside liner bush is easier to find )
– Put them together and line them up and weld them.
– Static balancing is good enough or go to the electric motor revision shop for a dynamic balancing they will do it for not much money
(ps I have never seen big unbalance results after shortening )