Winking reversing lights on my 1973 BMW tii seemed to call for a new switch, but lifting the cover over the gas tank revealed gas in the trough through which the wiring is routed. Tightening flange screws and hose clamps solved the problem.
Gear clash started appearing on the 1-2 shift, then turned into a grating before second gear was engaged. Then started grating on 3-N and 3-4. Synchros? No. The external shift linkage was loose, even scraping two 1/32 grooves on the shaft. Tightening the two allen nuts up top (manual calls them "socket head cup screws") restores noiseless shifts: $8 instead of $200.
Author: Ted Burakoff