Several causes:
- shaft drive oil overfilled so it escapes via the venting/pressure relief valve on the top of the bevel gear/differential and oil is spilled over the right side of the spoken will and tire side wall
- bad seal used for the bevel gear (image)
- wrong shaft drive oil used which is too thin and escapes via the bevel gear seal
- venting/pressure relief valve is blocked or dirty
Solutions: check the correct oil filling and use only the recommended shaft drive oil; check the proper function of the venting/pressure relief valve; improved seal to be used as following models affected: V85, V7, V9
Update August 1st 2019: main cause is probably excess pressure in the shaft drive due overfilling with shaft drive oil. The 180 cm3/ml - as mentioned in the manual - is the factory filling. When the oil is being replaced, the oil quantity has to be only 160 cm3/ml - as about 20 cm3/ml remains.
Solution: the correct quantity of shaft oil when replacing/servicing has to be
160 cm3/ml, also confirmed by Guzzi.
Solutions 2 & action since June 2019: The few damaged bevel gear seals including the shaft drives were and are being analyzed by Moto Guzzi to find the cause of the oil leak. The Guzzi warranty will cover this repair.
Constant quality checks are made on the supplied seals and production process has been improved to focus on delivering a rock-solid and fault free shaft drive.
Update September 15 2019: Only early V85 production models for the European market are affected, in average less than 2.5 % of the first series produced from March till May 2019 have a leaking bevel-gear issue.
All V85 for export round the world - except Europe - are rock-solid and fault-free.
Update December 12/16 2019: Moto Guzzi USA: NHTSA issues 2 recalls on Guzzi V85, dated Dec 2/3 2019.
--> - NHTSA - 2 Recalls 2020 Moto Guzzi V85 TT
The recalls are due to legal & warranty issues. Potential final shaft drive oil leak (371 Guzzi V85 affected) and potential defective footrest mounting pins (399 V85 affected).
Important: there are no NHTSA investigations or complaints known.
For Guzzi riders: check the potential final shaft drive oil leak before, during and after your ride - to be on the safe side. Only a few of the 371 Guzzi V85 produced during March-September 2019 may be affected.
