Replacing the drivebox oil seal – 21 Mar 2015.

As I’ve said before, I’ve had to do this several times on old Guzzis. Changing the seal is not a big deal but it took a while, on The-Big-Red-One, to get at it . It’s basically one stage further than getting the back wheel out. Luckily I’ve still got that bike jack I borrowed in the garage. So –

  • Panniers and frames off again.
  • Remove my newly fitted luggage rack.
  • Remove the silencers and exhaust crossover.
  • Loosen the rear axle nut.
  • Jack up the bike.
  • Disconnect the brake operating rod from the rear hub.
  • Disconnect the brake torque arm.
  • Slacken the axle pinch bolt on the swing arm.
  • Remove the axle.
  • Take out the back wheel complete with the brake backplate.
  • Remove the six bolts that secure the sump to the bottom of the bevel box and drain out the oil. I left it overnight.
  • Remove the right hand shock absorber.
  • Remove the four nuts holding the drivebox to the swing arm and pull it off. Mine pulled the driveshaft out with it so I just transferred that back to the swing arm.

I found that the gasket that should be between the bevel box and the swing arm was missing so made a new one ready for later.

I levered out the old oil seal and found, as I had predicted, that the surface of the splined drive hub that it runs on was coated in rust.


I spent an hour and a half with a scotchbrite pad cleaning up the surface and was pleased to find that there were no deep pits. A replacement seal should be all that’s needed.


The photos make it look like the drive hub has worn to a taper but that’s just caused by my camera.

I didn’t order a replacement seal from Guzzi as it’s a standard size and can be got cheaper and more quickly elsewhere. It’s 70x85x8mm. Originally the seals fitted were the single lip type and this is what came out of the box. The Guzzi parts supplier sites I looked on showed a twin lipped type as the replacement. They both cost the same from my bearing supplier and, although the second lip is really designed to prevent muck getting into the box rather than stopping oil coming out, I bought the twin lipped sort. I did this in the hope that the new seal, with its different profile might run on a fresh part of the drive hub.

To fit the new seal, I put a little grease on the drive hub and located the new seal with my fingers. I then put the old seal on top and upside down and used a piece of wood and mallet to knock it squarely into place.



To refit the bevel box I first greased the splines on the pinion shaft, added my new gasket and fitted the box to the driveshaft and swing arm but didn’t do the nuts up fully.


Before tightening the bevel box to swing arm nuts you need to get the box properly lined up in the swing arm. To do this I refit the axle.


I tighten those four nuts once the axle can be inserted easily.

This drive box is one of those made with the level plug in the wrong place. If you use this you won’t get anywhere near enough oil into the box. My V7Sport has the same type of box but the level plug is in the correct place. However, I still won’t use it as it’s very inaccurate. I have been told that the level reading is only right when the swing arm is level and to achieve this the shocks have to come off. Instead I drain the old oil out overnight then measure out the new oil (340ml of EP80w90 gear oil plus 20ml of Moly additive) using my high tech measuring bottle. This is what I did next.


After cleaning the wheel I greased the hub splines and refitted it with its brake plate and inserted the axle. I left the axle nut slack until the brake torque arm was back on then tightened it and the pinch bolt up properly. It was then a case of putting everything back together.

The following day I did 40 miles on the bike and the oil all stayed where it belongs!

Now that this bike is usable, it’s finally looking like I’ll be able to get back to working on Rhino, the V7Sport soon.


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