Small Block gearbox inputshaft seal

[agoldfish]

Hello all!

I have chased down an oil leak to the Gearbox input shaft seal, behind the clutch, and want to know (have confirmed) that I need to remove (how) the large nut on the input shaft in order to fit the seal without damaging it.

Many thanks!

[Old Jock]

First I know nothing about smallblocks & am only bumping the thread and telling you (what little) I know

That nut though closely resembles the nut on the Layshaft (output) of the 5 speeder box used on older Big Block bikes

On the BBs it's staked on the flare, I bet it's the same setup as the shaft has similar grooves in it too. So first the stake needs to be broken.

If its the same size as the BBs then you'll need a deep M27 socket to remove it and either a rattle gun (my preferred method) or lock the box at the output end and use a long breaker bar.

Remember I could be talking out my ass because I'm talking about Big Blocks, if it is the same it's torqued to about a zillion torques and a powerful rattle gun makes the job a whole lot easier

[guzzisteve]

What smallblock? 5sp or 6sp?       Just get service & parts manuals. It IS like OldJock says and goes into the primary part of trans. Most likely an oring on shaft under a spacer seal rides on.

[pehayes]

Are you sure it is the shaft's outer seal?  The older smallblocks also have a very small traditional seal fitted inside the other end of that input shaft which seals the throwout rod.  Are you sure the leak isn't coming up through the throwout rod bore?  Either way, I think you'll have to split the primary case away from the front of the actual gearbox.  Then you'll have access to remove that input shaft and easily change BOTH seals.  Likely you'll need a new gasket for the primary case.

Patrick Hayes
Fremont CA

[guzzisteve]

Must be a Monza, it's under his name.

[Antietam Classic Cycle]

Some videos here that might be helpful: https://www.thisoldtractor.com/moto_guzzi_technical_training_videos_eng.html

[agoldfish]

Thanks to all.

Yes, it is a 5 speed Monza Box.

I am pretty sure it is that seal, the pictures are Post-Clean-Up so don't really show the "evidence".

OK, deep 27mm socket on order. Bad Ass rattle gun on stand-by.

I have been in the Box before, to change the shift return spring, so kinda know my way around in there (that was a SH$T job BTW). I'll order both seals and a set of gaskets and get stuck in.

[Muzz]

OK, deep 27mm socket on order. Bad Ass rattle gun on stand-by.

There used to be on This Old Tractor a tutorial written by Nick Webb on how to attack a smallblock gearbox in the real world.  I even have it bookmarked.  Sadly, it seems to have disappeared, why I don't know but it's brilliant.  About four of us contributed on how we approached it, and Nick wrote it up.

If you have been in the box before Goldy you may be ok.  Guzzi did that front nut up to about 10 million foot tons.  I made the tools to do it.  If you have an old clutch plate lying around you can make a tool by cutting out the centre and welding a long handle on it; mine must almost be a metre long.  To make the spanner for the nut I would advise a 6 point socket.  The nut is very thin and easy to round off.  I spaced the handle so that I could actually clamp it to the body of the box so it didn't slide off the nut.  Once you are all set you can then undo the nut by turning the actual shaft.

I actually bought a Koken 6 pointer to make the nut spanner.  I also flattened the edge of it, as there is a slight radius on that bottom edge and the tool needs all the purchase on that nut it can get.

[Old Jock]

This one Muzz? It's hosted by Gregg Bender I think the site is a subset of "This Old Tractor" and is on Guzzitech DK, by Jens Lyck

https://www.thisoldtractor.com/guzzitech.dk/gb_en_complex-technical_gearbox-repair-breva-750-pictures.htm

John

[Pescatore]

This one Muzz? It's hosted by Gregg Bender I think the site is a subset of "This Old Tractor" and is on Guzzitech DK, by Jens Lyck

https://www.thisoldtractor.com/guzzitech.dk/gb_en_complex-technical_gearbox-repair-breva-750-pictures.htm

John

I was going to suggest the same.  I have been reading that document and others at that site: https://www.thisoldtractor.com/guzzitech.dk/gb_en_complex-technical.htm
It's a great resource that Old Jock has already pointed me to recently.

Unfortunately the posts that the document refers to have been deleted  .  If no activity, they get nuked.

Muzz, (and others referred in the document) did you happen to save that epic post?  http://wildguzzi.com/forum/index.php?topic=25247.0

Pescatore

[Muzz]

Old Jock and Pescatore, yes, that's the one.

Sadly, I didn't save it as I just used to go on to the site; easy because I bookmarked it.

I think I am the only one left standing from the original set of suspects.  My gearbox had problems from being an original Luigi Friday Special .  It kept blowing the hardening off 5th gear all the time.  The other three all had a pre-selector fork fault, where the fork used to jam up in it's body.  Guzzi quietly fixed it without telling anyone.  The funny thing was that although my bike was earlier, it had the later pattern fork fitted.  The two are indistinguishable with the naked eye.  The downside with the later pattern fork is that you need to remove the entire gear and shaft cluster, and re-installing the same can be "fun".  The official Guzzi stripdown with pictures is done with the early fork pattern.  With the later fork there was the four of us bouncing ideas off each other as to how to go about things.

If I can help in any way, feel free to ask.  I have been inside the box  (bit the bullet finally and put a second hand one in) a few times so have gained some insight on working on them.

edit: it's a shame it seems to have gone.  Nick's write-up was hilarious.

edit#2;  I will see if I can put some photos together of the tools I made and how they work, may take a day or three.

[Pescatore]

edit#2;  I will see if I can put some photos together of the tools I made and how they work, may take a day or three.

Much appreciated Muzz. I might post about a gear box problem, so I
won't hyjack this post.
I will add that the workshop manual I have shows how to
use the box frame to stop the nut, instead of two levers.




I'm wondering if anyone has tried this and if it could hurt the box.

[malik]

A photo of one of my gearboxes alongside the special tools. Hard to see clearly but the tools have bends customised to fit the bell housing. The modern smallblocks have a heavier input shaft and the clutch shaft nut is 36mm rather than the 27mm of some of the earlier boxes. The splines on the clutch shafts are different sizes as well. If anyone is lucky enough to have both modern & old smallblocks, it's likely they'll need two sets of the special tools.

Note - I last saw a copy of Nick Webb's gearbox article on thisoldtractor. It should still be there somewhere. Invaluable, as well as entertaining.

[Muzz]

Much appreciated Muzz. I might post about a gear box problem, so I
won't hyjack this post.
I will add that the workshop manual I have shows how to
use the box frame to stop the nut, instead of two levers.




I'm wondering if anyone has tried this and if it could hurt the box.

Once I haul the tools out of their hiding place above my wife's car...... I will take photos of , not only the tools, but how I use them.

Pescatore, I clamp the nut spanner to the box.  Will phonograph how I do it.  I have a complete spare box to demo on....

[Pescatore]

  

[Muzz]

Because you asked for it.



Centre shaft holding tool made from old clutch centre.



Close-up. Head is detachable so the critical bit can be couriered somewhere. Just add handle.



image url

Just a handle that can be bolted to the case as a steady if required.



The nut spanner. Has two ends. The final design is a 6 pointer socket.



The first (now superseded) end. Worked like a normal spanner. Was not happy with how it worked.


 
Final design. This is the 6 point socket with the spacer set so it can be clamped firmly to the case.



Like so. The nut is very thin, and at least here in NZ, it is a Guzzi part. I found a wheel nut off a car that will fit if I run a tap through it.
Picture shows how the spacer allows the spanner to be held firmly on the nut, and the nut is undone by swinging on the shaft tool.