rear drive problem

[charlie b]

OK, so the rear drive seal was leaking.  32 yrs old.  So, I got the seals and gasket and pulled it.  Everything looked pretty good.  Bearings moved freely, gear teeth looked in good shape. n Sorry if the pics are a bit out of focus



So, got ready tackle the seals.  But, noticed this...

and this

and of course the coupling


So, now I suspect something is causing this, which might have caused enough heat to screw up the seals.  But, what?
One laset data point.  The inner bearing race is loose in teh housing, ie, it will rotate just a tad, at room temp.  Does that mean enough heat to do something to the case itself?

I guess I am a bit 'lucky' cause I can get the replacement ring/pinon for the 7/33 rear end.  But, I don't want to replacee all the guts and then have it happen again.

[fotoguzzi]

what's the mileage? looks like a lot..

[Idontwantapickle]

Those gears look good but that pinion spline is toast. That's a bummer, you'll be needing all that stuff replaced. The bearing issue can be addressed along with it.
The wear on the splines is from lack of lubrication and possibly mis-alignment of the box on the swingarm. It's pretty common for these to wear like this unfortunately.

[charlie b]

94k miles

the other end of the drive shaft looks fine.

[Antietam Classic Cycle]

So, now I suspect something is causing this, which might have caused enough heat to screw up the seals.  But, what?

One last data point.  The inner bearing race is loose in the housing, ie, it will rotate just a tad, at room temp.  Does that mean enough heat to do something to the case itself?

Splines not being greased enough or with a grease not up to the job is mostly to blame for the spline wear, IMO.

If you mean the outer race of the needle bearing was loose in the housing, that's not as uncommon as you might think on that type of housing. I've found it necessary to apply Loctite 609 to several I've had open for seals.

[pete roper]

Spline wear, especially on high mileage bikes, is common. It's a good idea to keep the splines greased but obviously grease will get flung off and splines will wear.

One trick commonly used when things get this bad is to weld a new coupling to the pinion and then use a new driveshaft. This will prolong the life of the pinion but does mean that when the time does come to swap the gears out it is more difficult. Bevelbox castings and pinion carriers are ten a penny though so prolonging the life of the gears in this way and then building another box from scratch for when it finally fails is probably the best way forward.

Pete

[rodekyll]

Why?

Biggie is the cush drive in the rear wheel frozen.  It's there to help those bits not slam around when you load/unload/reverse load the splines.  Lube helps too.  Then there's the slamming around of sportish riding -- hard throttle-to-rapid engine braking and standing on the brakes all serve to wear the splines down.  From the shape of yours, it's had a history of abrupt engine braking-to-brisk-throttle-and back transitions.  Not saying that's a bad thing, just that this is the tradeoff for treating every day like track day, especially when the cush stuff isn't working.

[charlie b]

Thanks all.

The last time I had it apart was almost 6 years ago (probably part of the problem, eh?).  Greased it with moly grease, don't remember the type or brand.

And, no, it has not had a gentle life.  I do tend to twist the throttle a bit and it sees daily commuting use in stop and go traffic.

I'll pull the cush drive and see what it looks like as well.

A local (Forslund) will rebuild it for me so that part isn't a problem.  If it was an 8/33 drive he has a spare sitting on the bench.  Oh well.

Pete, I like your idea and will consider that instead of buying new gears.  But, how do you weld it and not screw up the pinion bearing?  It doesn't heat up fast enough to overheat the bearing?

[Wayne Orwig]

Been there, done that, on two over 100K mile Guzzis.

On the second go around, I thought it was related to too tight a cush drive in the rear wheel. So I kept that system free moving, greased, and took some of the rubber wedges out of the rear wheel. What I ended up doing was wearing out the cush drive system, and then needing to replace the rear wheel. That was expensive

I always tried to keep those splines greased, but I believe it is related to moisture. Over the years, and a quarter million miles, I have found that grease does not stay in there. Plus there is always a bit of rust when I check those splines at the rear. I have never seen any wear at the transmission end, just at the rear drive end.

This is a photo of an EV I worked on last year, not mine. And you can tell there is a huge amount of rust in the grease. Yet the transmission end was fine. I often see almost the same thing on mine. Not sure why.



I have gotten where I pull it apart, clean it well, grease everything and slide the coupler on, PACK the coupler with a tacky grease, and then force the rear spline back in there with grease going everywhere. No idea if it helps, but it makes me feel better.

[pete mcgee]

Charlie,
94,000 miles?, you just can't buy quality anymore eh.
In all seriousness you've done well, the drive shaft and splined joiner are a service item IMO.
The splines on the pinion can be welded up and recut, I've had that done once, I've also replaced the ring and pinion gear once in 200,000 miles. In all probability it will go back together with the same shims.
And that's with me pulling the bevel box off every second oil change to grease the splines.
Bearing spinning in the housing, loctite make several grades of bearing lock for just that issue, plus you could stake the bearing in a couple of places as well.
Entropy starts the minute you ride it, its all part of ownership of anything mechanical.
There's nothing special sized or exotic in there, all the bearings can still be bought fix it and keep riding.

Cheers

[charlie b]

So, why moisture down there?

Come to think of it.  Gearbox lube is to be forced up through the pinion bearing when it gets hot.  If it doesn't get hot enough then maybe it doesn't get enough lube through the pinion to the splines?

Rear splines cause they are 'downhill' from the front.  Any moisture will collect at the back end?

Just guessing.

Anyone ever cross drill and pin the coupler to the pinion shaft instead of welding it?

[rodekyll]

Charlie,
94,000 miles?, you just can't buy quality anymore eh.
In all seriousness you've done well, the drive shaft and splined joiner are a service item IMO.
The splines on the pinion can be welded up and recut, I've had that done once, I've also replaced the ring and pinion gear once in 200,000 miles. In all probability it will go back together with the same shims.
And that's with me pulling the bevel box off every second oil change to grease the splines.
Bearing spinning in the housing, loctite make several grades of bearing lock for just that issue, plus you could stake the bearing in a couple of places as well.
Entropy starts the minute you ride it, its all part of ownership of anything mechanical.
There's nothing special sized or exotic in there, all the bearings can still be bought fix it and keep riding.

Cheers

Pete Mcgee -- I have had a pinion shaft recut (10-spline).  It came back from the shop in what can be most graciously called a 'raw' form.  The broach work is a bit rough and not hardened in any way.  I'm looking at raw cut, shiny metal, which looks dubiously soft to my untrained eye.  I'm not planning to use it until I know it's right -- When you had yours done, did you have the work hardened/rehardened?

[acogoff]

     I was doing some work in Ithaca NY about 30 years ago and used a machine shop (it was in his house)while there and he specialized in fixing worn out Saab 99 drives which uses a very similar shaft size to the guzzis. His fix was to broach a keyway in the shaft and furnace braze a large half moon key in it and broach a keyway in the mating part for the new shaft set up. He said they went just as long as the original and then some.

[charlie b]

And the cush drives are nice and 'cushy'  :)  There are only six and space for 12.

[fotoguzzi]

Charlie,
94,000 miles?, you just can't buy quality anymore eh.
 
Cheers

you got a rear drive problem at 94k?  NICE! fix and ride for many more miles..

[rodekyll]

Are perchance the pie pucks perforated profusely?

It's a common trick to use every other pair of pucks and sometimes drill them to make it cushier back there.  It helps the splines but as pointed out above, can damage a wheel if it goes wrong.

[jacksonracingcomau]

I've had sleeve welded many times, I like to get last mile and spline worn out before gear faces bugs me
Never remade the spline but there are people who can do this

Latest set of gears would break the weld, not instantly but 10-20K miles, weld again, gear faces sill good, cost a sleeve and shaft every year
Along with resetting UJ in bearing, always the clue, UJ spinning in bearing

Finally got assembly to serious engineer, forgotten more than I will ever know , there are marks on pinion now but I told him I want last 40K miles, he smiled and understood,  I gave him new bearing and machined UJ yoke, he made a pointer that fitted into UJ yoke and set swinging arm in mill
I was certain it was all perfect as every time I've fitted newly welded sleeve there is no resistance turning bolted up bits but still spline wears or weld cracks.

So he machined face for pinion flange square to pointer, both north south and east west
Then welded sleeve on worn pinion gear again, this time in jig to keep square, this was very tricky to do.
Whether the square weld or the aligned UJ/pinion was the major I'll never know but combined it's done it, 20K odd
Took apart recently, grease still intact, no rust, UJ not spinning

My "other" bike in UK did opposite last year, only around 140,000 miles on this one but was feeling vibey so took apart
second UJ in it's life was spinning in bearing but crosses good, turned it around (emery cloth to size)
Shaft, sleeve, pinion gear, cush gears (male and female) all completely Donald, all OE original owned since new
Made this souvenir for my bro , I like it, everything worn together, last miles from all, 140K reasonable I think
Pic is French hillclimb, may or may not have been where the missing pinion tooth went !


Interesting to some maybe
Fitted Ago alloy timing gears when new, same mileage as these gears, no reason to look at them yet !!

[pete mcgee]

Pete Mcgee -- I have had a pinion shaft recut (10-spline).  It came back from the shop in what can be most graciously called a 'raw' form.  The broach work is a bit rough and not hardened in any way.  I'm looking at raw cut, shiny metal, which looks dubiously soft to my untrained eye.  I'm not planning to use it until I know it's right -- When you had yours done, did you have the work hardened/rehardened?

Rodekyll
Looking back at my records I had it done in march 2001 roughly 30,000 miles ago.
I had it out for a regrease 5000 miles ago and didn't notice a lot of wear, the sleeve was still a firm fit onto it.
I have very vague memories of being told they used a hardening weld on it when they built it up and recut it.
If you think yours is soft run a file over a spot on it and compare it to the one fitted next time you have it out to grease.
I left it in the capable hands of the local Brisbane Guzzi guru who's been working on them since childhood, he took over his old mans business, he has contacts to fix everything, that's what he does and he's good at it.
I can't remember a different colour so they may have treated it after welding.
That's all I can tell you/remember.
Hope that helps.

[sib]

I've noticed some of the comments address the problem of grease being flung out of the splines.  I was recently exploring greases and noticed that Shell markets a grease specifically made for splines and helicopter rotor drives.  It's called Aeroshell Grease 14.  From the brochure "Apart from its general purpose application for helicopters AeroShell Grease 14 is also recommended when anti-fret and anti-corrosion properties are required, e.g. splines."  This looks like a good bet for our Moto Guzzi drive splines.

[charlie b]

Are perchance the pie pucks perforated profusely?

It's a common trick to use every other pair of pucks and sometimes drill them to make it cushier back there.  It helps the splines but as pointed out above, can damage a wheel if it goes wrong.

Not profusely, just two holes each.  I am surprised they are in such good shape.

I've noticed some of the comments address the problem of grease being flung out of the splines.  I was recently exploring greases and noticed that Shell markets a grease specifically made for splines and helicopter rotor drives.  It's called Aeroshell Grease 14.  From the brochure "Apart from its general purpose application for helicopters AeroShell Grease 14 is also recommended when anti-fret and anti-corrosion properties are required, e.g. splines."  This looks like a good bet for our Moto Guzzi drive splines.

I may look for some of that stuff when I reinstall it.

Since I have it half apart I may take the time I have to remove the rear swingarm and replace the clutch pushrod seals and the ujoint boot, maybe even the ujoint carrier bearing.  It was replaced the last time I had it apart, 6yrs and 40k miles ago  :)

PS Matt is going to look for a used rear drive when he is at the Nationals for me too.

[charlie b]

If you mean the outer race of the needle bearing was loose in the housing, that's not as uncommon as you might think on that type of housing. I've found it necessary to apply Loctite 609 to several I've had open for seals.

Thanks for this too Charlie.  I was beginning to think I had buggered it up somehow.  Especially after seeing all the issues some people have with removing that race from the drive housing.

[jacksonracingcomau]

maybe even the ujoint carrier bearing.  It was replaced the last time I had it apart, 6yrs and 40k miles ago  :)

check UJ hasn't spun in bearing, as I said above always goes with worn drive splines IMHE

[pete mcgee]

Any idea why Martin?

[jacksonracingcomau]

Any idea why Martin?

I wrote an essay about 10 posts back
Fixed now, pinion aligned to UJ, swiningarm in mill

But why some do and some don't from new is what we have to call a Luigi moment
I've "fixed" spinning UJ's 100's of times without really solving problem, symptom and cause, this time I've fixed the cause, by asking someone cleverer than me.

Grease missing or UJ spinning are the symptoms not the causes, as is spline wear.
Pinion bearing loose or worn will do same thing, cause all to wear.

For most people it only happens once or twice in their lives so not an issue but I've done it too many times, had to find out, I owe the man a drink

Happy to share knowledge

[charlie b]

I am going to be pulling the swingarm in the next week or so.  Will probably just replace the Ujoint bearing while in there (no reason not to).  It was replaced 30k miles ago when I had it apart last.  Will be interesting to see if it is wonky too.

[charlie b]

Recent update.

Pulled the swingarm.  All looked nice and greasy in there with dripping rear drive oil.  The ujoint and support bearing looked nice and clean with no sign of ujoint spinning in bearing.  I will change the bearing...just because I am in there.  The current one has over 30k miles on it (maybe even 40k miles).

Ujoint.  I know this is the original and it has never been apart.  Is it recommended to disassemble and grease it?  It still feels nice and smooth with no notchiness (?).  I've done car ujoints before but they also have zerk fittings on them to grease them.

[Chuck in Indiana]

Pete, I like your idea and will consider that instead of buying new gears.  But, how do you weld it and not screw up the pinion bearing?  It doesn't heat up fast enough to overheat the bearing?

Do many spot welds, giving time for each to cool. It helps to have a dial indicator to keep everything (fairly) straight as you're doing it. Spot, rotate and indicate, tap as necessary for it to run true, repeat. You can keep it within a few thousandths, which is plenty close enough.

[rodekyll]

Charlie, I don't usually see "All looked nice. . .." and "dripping rear drive oil" in the same sentence.  Can you be more specific about this part?

[charlie b]

RK, just trying to say that the swingarm section was wet with rear drive fluid, not dry.  It is a good thing that there is oil getting up in there cause then I know the bearings are getting some lube.

Thanks Chuck.  Would using a cross pin help at all?  Maybe a tapered pin that is spot welded to keep it in place?

May be a moot point.  Looks like I will be able to get a rear drive from another bike.

[rodekyll]

Gear oil in the swingarm behind the carrier bearing could indicate negative swingarm angles -- short shocks or undersprung.  The carrier bearing is sealed -- doesn't need lube and bathed in gear oil it could wash out its grease.  Negative arm angles can drain the lube from the punkin and add it to the gearbox

Gear oil in the swingarm ahead of the carrier bearing could indicate a bad rear seal or bad output shaft bearing.  If gear oil washes the u-joints they will dry out. 

So be sure nothing bad is happening . . . . .