Shift Shaft Weep

[Antiquar]

Hey Guzzi folks. Hopefully this will be the last weep related thread I post for a while.   

I recently resealed and reshimmed (amazing what one shim will do... 0.8mm to 1mm and the damn thing shifts so much better) the 5 speed gearbox on my G5. I noticed after a nice ride on the highway today some oil weepage from the shift shaft--a drop collected on the bottom of the shift shaft boss. I haven't noticed anything from there riding around town.


It being a pretty simple seal I can imagine oil can weep from there when the box is under pressure. Is this common? Running 75w90 GL5 in the box now.

It's not such a big deal that I will pull the box again any time soon, just curious what the board will say.

[LesP]

I applied rubber grease to a suitable sized O-ring that went between the case and shift arm...........

Edit.
I have the stock 5 speed internal O-ring with rubber grease along with the external one which is also to stop any grit getting to the shaft, same reason I used the modified Ducati clutch lever bellows as a grit/water seal at the clutch push rod plunger.

[Antiquar]

I applied rubber grease to a suitable sized O-ring that went between the case and shift arm...........

So you get weepage as well, eh?

Clever solution, I'll give that supplemental oring a try. 

[LesP]

Not to date, but will update that if the bike ever gets beyond the the dining room.

[pehayes]

The transmission box should be open to atmosphere.  No internal pressure development.

When you did the restoration, did you replace the shift shaft o-ring inside the rear cover?

The 5- speeds have a shift shaft o-ring seal.  The 4-speeds do not.  When asked, I modify the 4-speed shift housing to accept the same o-ring as the 5-speed.

If you want to get anal about the drip, you could always run a few cc's shy of full.

Patrick Hayes
Fremont CA

[Antiquar]

The transmission box should be open to atmosphere.  No internal pressure development.

When you did the restoration, did you replace the shift shaft o-ring inside the rear cover?

The 5- speeds have a shift shaft o-ring seal.  The 4-speeds do not.  When asked, I modify the 4-speed shift housing to accept the same o-ring as the 5-speed.

If you want to get anal about the drip, you could always run a few cc's shy of full.

Patrick Hayes
Fremont CA

Hi Patrick, thanks for the response as always.

I did renew the shift shaft oring in the gearbox cover, so I'm a little surprised about this weep. I haven't noticed any drippage from the vent line (vent barb is definitely open. it's the early type that doubles as the detent spring plug). I run a long vent line to the rear of the bike as I hate the idea of gear oil being deposited directly in front of the rear wheel... not sure if that is having repercussions.

The funny thing is my T3 has a weep in the same spot... but I haven't opened up that gearbox so I don't hold it to the same standard. 

I unfortunately am very anal about drips... especially after doing the work. Considering trying out a slightly thicker oil as well.

[pehayes]

Considering trying out a slightly thicker oil as well.

OK, so what oil are  you currently using?  Some brands foam up much worse than others.  That's a good thing for the foam to push some lubricant to hidden places, but a bad thing if there are any vents that could allow a weep.

Patrick Hayes
Fremont CA

[Antiquar]

OK, so what oil are  you currently using?  Some brands foam up much worse than others.  That's a good thing for the foam to push some lubricant to hidden places, but a bad thing if there are any vents that could allow a weep.

Patrick Hayes
Fremont CA

Interesting. Right now I've got Valvoline High Performance SAE 75W-90 in the gearbox.

[Antiquar]

I shortened my vent tube and rigged a catch can and got a few ml of blown gear oil. I measured 750ml when I filled the thing, so it shouldn't be blowing any really.

Ordered some BelRay 80W/90 that many on the board recommend and will give that a try.

[Tom H]

I tried Valvoline many years ago. I had more drips from my breather hose than with StaLube. BTW: I use Valvoline engine oil, so I do like the brand.

Tom

[e.cleven]

Shift Shaft, Weep....
Try saying that five times real fast..

Just having fun.

Earl

[Antiquar]

Shift Shaft, Weep....
Try saying that five times real fast..

Just having fun.

Earl

Helps if you take a swig of 90wt first. 


Well I tried the Belray 80W/90. The box shifts a little nicer but still leaking. Oh well! Frustrating because I replaced the damned oring. Thanks for the advice everyone!

[Antiquar]

To conclude this post--the story of one of the most petty and minor of annoyances to be found on this vintage Guzzi--it's fixed. I read up on the gearbox chapter of Guzziology, where an oversize oring is recommended. I tracked down the size of the oring (14x3--0.5mm larger diameter than standard spec) and ordered a batch from McMaster-Carr.

No more weeping, the shift shaft is now dry.

In the pay it forward spirit endemic to these boards (and because I have 100 of these suckers), I'd be happy to send anyone one or two for your bike if you need 'em.