Rear drive breather
Moto Guzzi V700, V7 Special, Ambassador, 850 GT, 850 GT California, Eldorado, and 850 California Police models
While the rear drive should not need a breather in order to prevent leaks, adding a breather continues to be a fairly common modification. Steve Hilhorst sent me a description of his nicely implemented solution. In Steve's own words:
I have had a very minor oil leak from the rear drive. I am unsure if it has ever been overhauled or had the seals replaced. As the leak is very minor I decided to fit a breather on the rear drive to ensure there is no pressure build up that could force oil past the seals.
I got a differential breather from an auto wrecking yard and fitted it to the rear drive fill plug. The breather has a little valve inside it and is originally from an old Toyota Celica, but I believe the same breather has been used by Toyota for a very long time now, on many different models (Toyota part number 90930-03031; thread size is 10 mm × 1 mm).
Took it for a ride after fitment and all appears good, no splashing of oil out the breather. I will have to do a few more miles before I will know if the leak returns or not.