T3 bevel box drain with swinging arm?

Having just been to the Kupferpaste and back, my bevel box started leaking once the air temperature hit 35. Â The temperature then got to 40 for much of the time, and the box leaked a fair bit. Â

On returning home I drained the box, and the leak can’t have been that bad, indeed I may have previously overfilled the box. Â The level plug thread is on the way out, so I have now glued that in for good (as advised by guzzilology and others) and will in future measure the oil to put in (230ml HP80/90 + 20ml moly).

I’m not going to try and replace the seal(s) before the V-twin, but I do have one little nagging doubt.Â

A while ago I replaced the o-ring between the bevel box and the swinging arm. Â For some reason something in my head is saying that there is a drain slot in between the box and the arm, and that I could have assembled this so as to block the drain.

So is there such a drain on the T3, and if blocked, could it have caused, or at least exacerbated, the leak? I could take the box off now to take a look, but being the mechanic I am (i.e. not good at all) I don’t want to fiddle unless I have to.

I am sure there was an article on this very subject within the last few gambo’s.
See you at the 40th V Twin anyway.

I’ll have a look. Â I know something tickled my brain cells about the topic but I’ve failed to track it down as yet. Â

Meanwhile I’ll see you at the 39th :unamused:

Yes, I have now found it in the May/June edition - thanks.

It’s about a different model (an 850 GT), and is more about oil getting into the gearbox from the bevel box (a deep long mystery in Guzziology) than causing a leak from the box.

Would a misalignment of the oil drain holes cause a leak? Â I imagine the bevel box would breath through the bearing anyway, would it not?Â

It was my 850GT. I think the slots are there on all of the big block bikes, but you can only misalign them if the pinion carrier is in the wrong position. In my case it was filling the gearbox up, and leaking out at the UJ gaiter. I suppose if the swingarm is full of oil it will come out wherever it can.
Although I fixed the original problem I have subsequently had a leak at the joint to the swing arm. There is an O-ring between the pinion carrier and bevel casing, and a gasket between the pinion carrier and swingarm. I had re-used the gasket so just made a new one and problem is fixed.
It always leaks at the filler until I have cracked it open to de-pressurise when hot - I think this is quite a well-known procedure.


Yes it is, I used to burp my lemon after every service.
I have seen bleed nipples screwed into the filler caps with a piece of pipe heading vertically up the shock before turning over to keep the rain out.
Of course modern Guzzi’s have a breather built into the filler cap.

Thanks. Â I have noticed that some pictures of the paper gaskets don’t seem to have slots, and some do, which is strange. Â I guess I should take a look, but I have no spare gaskets at present and it’s not leaking there (yet…). Â

Well well. Â I’ve never heard of this, and I’ve only been riding the same T3 since 1977. Â

Of course it is entirely possible that I’ve been told about this many times, and have forgotten. :wink:

Being unable to restrain my curiosity I took the bevel box off this afternoon (without having to completely remove the rear wheel from underneath the mudguard which involves far too much disassembly for my lazy taste).

The T3 box is clearly not the same as the 850 GT. Â There is only one drain slot at bottom centre. Â The paper gasket (which I managed not to break) doesn’t have a cut-away there, but no oil drained out of the swinging arm, so I don’t think this is the cause of my problems. Â There are, more ominously, many signs of a leak from the large oil seal. Â I have put the box back on as it is for now, not wanting to tempt fate with disassembling the bevel box for the first time in my, or its, life. Â Assuming it does leak again to and from the v-twin it’s job for later this year. Â I seem to have a new large oil seal in my pile of gaskets and seals, and the outer gasket as well, Â Whether I have an inner seal only time will tell. Â I guess I should try and replace that at the same time, and check the bearing. Â I will attempt to avoid looking at the gears, which are probably quite old…

If it doesn’t leak again I shall smile, blame climate change for the heat in Germany, and probably still change the seal on the basis that if it has leaked once it will do so again, and 77,000 miles and 40 years isn’t a bad age to retire. Â

The large oil seal can most easily be prised out and replaced with new without opening the box. It’s the small interior seal that’s the total PITA requiring a complete box strip. Â

PS: last NEW large seal I bought included an extra flange creating like a double lip to help keep the oil in, never seen that before, was mail ordered from Gutsibits.Â

Thanks. I think after all these years & miles I had better follow guzziology on the matter, which includes ‘preparing the surface’ by scrubbing it a little, meaning the cover will have to come off. I’ll have much of the winter to faff about. I just need to school myself to take things slowly…

One question. How would I know if the small seal is leaking? Where would the oil come out?

oil would come out at the axel and make a mess,over filling would look the same

OK - thanks very much. Â I thought it might be that but wasn’t quite sure, never having had the box apart. Â When I took the axle out just to take a look at the box it was a little oily - not a lot, but…Â

More likely it comes out along the spindle to the wheel hub, thence the hub splines thence the rest of the wheel and tyre, if however you get it on wheel and tyre BUT the spindle is ‘dry’, then it’s the large seal not the small interior seal.Â

Not heard of that, but then, TBH I’ve not read Guzziology.Â

I just dug old seal out, Â tapped new one in, no more leaks, proper job.Â

Easy to do hence worth a try.

Thanks. If I get further problems I’ll look into adding a breather.

I looked at this but found that for my Cali all I need to do is burp the bevel box.

However, I found that you can get a metric equivalent of this http://www.flowfitonline.com/mintor-accessories/mintor-accessories-for-hydraulic-components/hydraulic-oil-filling-plug-with-breather-14-bsp-tsf1g ref TSFT/N IIRC

I couldn’t find any other supplers in the UK apart from Flowfit, but I guess a trip to your local hydraulic/gearbox specialisyt might bear fruit

The only thing is that I wouldn’t want to lose the magnet for bits of swarf. Â It doesn’t collect much, but I guess it serves a purpose doesn’t it?