The most common cause of gearbox damage is water penetration via the cover of the speedometer cable. The grommet prevents this reliably with a newly engineered shape. Replace your grommet if it is porous or badly weathered.

The speedometer cable boot is an Achilles' heel on the two valve twins that was never upgraded. The rubber deteriorates with time and the seal around the cable becomes loose. Water may enter the transmission and if gone unchecked mat result in the failure of your transmission bearing - all because of a little rubber boot.

The Siebenrock Speedo Cable Boot first of all is made of Nitrile Butadiene Rubber (NBR) which is a synthetic rubber that is highly resistant to oil. In addition, the hole in the boot places a much tighter seal around the speedometer cable than the original boot, so the water runs down the outside, away from the cable and it stays out of the transmission.

The highly flexible material combined with the shape and oil resistant properties will make this the last speed cable boot that you will need to buy.