V50 / Small block (transmission) gear whine

[R1100purist]

Hi all! So I have been getting on the road more with my refreshed 1996 V50 P.A. And i have noticed it has a pronounced gear whine I believe it coming from the transmission when the bike it in (any) gear and under load. I.e. when in neutral, clutch in or out or when coasting, power off. So I think that rules out the final drive.

Having never ridden another small block Before this are these known for a pronounced gear whine that rises in pitch with revs or do I have a bearing in the transmission I need to replace?

[Chuck in Indiana]

Normally, the whine is worst in fifth. It is caused by low oil levels recommended by the factory  because people were griping about oil mist out the breather. Fifth gets starved the worst. If it's loud, it's toast. I *little* whine is normal.

[Guido Valvole]

If oil doesn't come out the check/fill point when the bike is on its center stand, there isn't enough inside. Official line is to have someone holding the bike to the side when filling. You can do well enough just using the side stand when filling. It probably won't automatically retract,probably. And oil will go out the breather anyway. There's an improvement over the stock breather that will stop oil pooling on top of the transmission.

[malik]

Bearing in mind (pun intended) that I don't know all that much, and that my experience (little though it is) is with the later smallblocks (they are not so very different from the older ones), if you've whining in all gears, I'd guess that you'd better look at the components that are common to all gears. My 2014 V7 (only 115,000km) has now started whining in 5th gear, but I know that the hardening on the 5th gear dogs is flaking off - it wasn't whining when I had the gearbox apart - would have replaced them, but the price of one of the dogs was prohibitive, so I cleaning up everything, replaced most of the bearings in the gearbox & buttoned it back up. 4,000km later, the whine in 5th started. The gear changes did seem smoother afterwards, though. I also get a bit of whine in 1st and sometimes in 4th (I notice it now that I'm sensitive to it). I get no such whines in the 220,000km 2010 V7.

I would suspect a bearing, or more than one - they all revolve around the shafts, or the bearings or the bevels in the final drive, and it would be worth checking the drive shaft splines at the uni joint and at the final drive end. Good quality replacement bearings are available fairly cheaply from the bearing shops.

Hopefully, someone with more experience & a better idea of what's going on will weight in with pertinent advice. Try the smallblock forum on groups.io - there's likely a wealth of experience there waiting to be tapped. I shall be very interested in whatever you find. Keep us informed, please. And good luck.

Mal.

[Huzo]

When giving descriptions mate, you have do be absolutely definitive in describing your symptoms.
When you say “power off” when coasting, do mean “throttle off” or “engine off”.
Also “rises and falls with revs”.
As you accelerate gently up to speed, does the whine alter in pitch with the increasing wheel revs and more importantly, does the pitch stay the same at say 4,000 rpm in 3rd and remain unaltered as you grab 4th and the engine revs drop down to 3,500 ?
If the whine is linear with wheel rpm, then it’s from the output shaft back.
If it’s linear with engine rpm, then it’s input shaft forwards.
Try taking the bike up to speed and note the whine, then pull in the clutch and cut the engine with the ignition switch,
If the whine stops it’s input shaft or forward, if not then it’s output shaft or back..

[Chuck in Indiana]

The old small block breather fix is detailed here on page 3.. along with a lot of other small block stuff.
https://wildguzzi.com/forum/index.php?topic=89034.60

[R1100purist]

Well awesome replies everyone. And those who pointed out I should be more accurate in my descriptions of the problem are right. To the best of my knowledge I had indeed filled it with a full liter of the good stuff. However I’ll drain, inspect for particles and then go on a ride again. The whine is indeed in all gears and it changes with the rpm, when I shift then it just lowers in pitch until the revs come up again. I will try the engine kill today to see what happens as well and report back.





A little snapshot from less whiney times.

[Huzo]

I’m guessing a bearing on the input shaft.
If it was on the output shaft, the pitch would not drop because the drive shaft is doing the same rpm at 3,500 rpm in third as 4,000 rpm in second..(as an example.)
Beautiful shot of your little child BTW..
That’s how it starts..

[R1100purist]

Thanks Huzo, that was from a bit a go, he is a little over 2 now and while more difficult I hope the motorcycle/garage worker interest will rub off on him.

I agree after experimenting today it sounds like it’s the input shaft bearing. Some interesting observations: I only hear the whine when the transmission is under load. At a steady state cruise/neutral throttle it is not there. Above 5k  it’s not as prominent either. Finally 5th gear is no worse than the other gears.

I replaced the trans oil this morning. And my brother helped tip the bike all the way over to get the full liter in. The old oil had a little fuzz on the magnet but nothing crazy. The oil was also a bit dark, with a faint metallic sheen. So that could be the early sign of impending bearing failure.

Does anyone have a good transmission tear down guide? How hard is it to get to that bearing?

[malik]

........

Does anyone have a good transmission tear down guide? How hard is it to get to that bearing?

There may be something in Guzziology, the thisoldtractor archives, some of the smallblock forums. I like the Breva 750 Gearbox Repair guide found on the Moto-Guzzi-750@groups.io and on thisoldtractor - the gearbox on the later smallblocks is not significantly different. There should be some guides on the older smallblock stuff penned by Rod Yeomans, but that would be prior to 2015.

You'll need to acquire or fabricate a couple of special tools - one to hold the clutch shaft (from an old clutch centre), the other to fit the nut on the clutch shaft (I had a 36mm sacrificial socket cut down & welded into a lever - fits the later 750, but I've an older smallblock box that has a smaller shaft & nut).

Note that a heat gun might be useful to help loosen the locktite on the clutch cover screws. Last time I had trouble getting a couple of them out & they had only been in there since 2014. I found good quality, impact driver standard, Allen key sockets invaluable.

Once you are in there, and the clutch cover is off the transmission cage, mostly it's all pretty obvious. I don't know about the earlier smallblocks, but to get the gear castle off the gearbox cover on the 750's required long 4 & 5mm Allen keys - the T handled ones from Bondhaus made the job easier.

Also note, the oversight of someone who know what he's looking at in there can save tons of grief. And another pair of hands helps a lot. See if you can't arrange these too.

[Antietam Classic Cycle]

Does anyone have a good transmission tear down guide? How hard is it to get to that bearing?

Scroll down near the bottom for a series of good videos: http://thisoldtractor.com/moto_guzzi_technical_training_videos_eng.html

[Muzz]

Does anyone have a good transmission tear down guide? How hard is it to get to that bearing?

http://www.thisoldtractor.com/guzzitech.dk/pdf/gearbox-repair-breva-750-nick-webb.pdf

This informative and highly entertaining read was compiled by Nick Webb.  Four of us had gearbox problems at the same time.  Sadly, the genuine Moto Guzzi stripdown leaves a lot to be desired.  Three had a pre-selector fork problem, where the gearbox decides to stop shifting. (Guzzi quietly modified the part and said nothing) whereas I had the dreaded 5th gear shred.

He documents the slightly differing approaches we all took to get the job done.  I suspect that your V50 won't have the same problem getting the gear stack in/out, as the later (by about 2004) pre-selector fork is the thing that causes the problems.

If you do decide to get the gear stack out I have found that a long, heavy duty zip tie loosely done up is the bees knees to hold it all together.  With the later fork, which I don't think you will have, you are trying to stuff two shafts, the selector drum, the pre-selector fork and engage the indent spring all at the same time.

Best of British Italian!

[huub]

If you can bear the sound, dont worry, all the early smallblocks are like that.
repair is possible but too expensive to make it a viable option.

My V65TT gearbox ( same as your V50 box) whined when i bought it, and still does so 100.000 tough miles later.
the box is bullet proof, just a bit noisy.
on my TT it is the primary gears in the box are the noisy ones.
might be the same on yours.
you can quieten the box a bit by overfilling , using 110 weight synthetic gear oil , and my favorite , using some MOS2 oil additive .
or a combination of all above.
But best is to live with it, no small furry animals get harmed, and it is a 25 year old bike.
 

[Mayor_of_BBQ]

I get no gear whine under load in any gear, but I have an improved breather and fill with 1L of fluid.  Downshifting/engine breaking, it wails like a banshee in the best possible way

[R1100purist]

Everyone! Thanks for the really thoughtful replies. Muzz and Huub get specific shout out for the long detailed posts.

To wrap this up as no one likes an inconclusive thread. My plan is to hunt around for a new small block gear box to swap in for the time being and then begin a leisurely stroll through my original gear box as the noise is now something I focus on too much (ocd). It’s a great bike and I will post  my process to hopefully illuminate my findings.

[Muzz]

R1100.

Looking back I see you have a '96.

Steamdriven on this site has a Monzada, a 500 Monza with a 750 carbed Nevada engine in it.  It was definitely not a straight swap.  He wanted it to look as original as possible.  A lovely looking bike but it took him about two years to pull it off.  The gearbox input shaft is different from the later ones, as is the output shaft, which means the UJ is different from the later ones.  He had a lot of trouble linking the later box of the Nevada on to the drive shaft of the Monza.  If you intend to use the Monza motor the later boxes will not be a straight swap.

The input shaft holding tool that he had built was a different size to the shaft on mine, so I had to build another from an old clutch centre.

He did say has old Monza box used to make a terrible whine, so he stripped it down to check it at a large mileage.  Found it was perfect so put it back together.  He put something like 70,000 (miles or kms, not sure) on it before he did the motor swap.

[R1100purist]

Okay, so long story short I finally got into the gearbox. To my surprise everything looks fine except there is some black residue/powder in the low spots of the trans mixed in with the gear oil and maybe the front output shaft bearing has some play.

I was hoping to find something catastrophic but alas. The only question is, looking at this gear, there are some grooves, I don’t think this would cause a whine though :/

[Chuck in Indiana]

Someone with more experience than me will be along, but as I said before, some whine is normal. They are straight cut, after all.
(Thinly disguised bump to the top)

[huub]

you might also check the primary gears, they can get noisy too.
the gears on the pic look pretty worn, but they will run for another 100.000 km if you can bear the sound.

[Rolf Halvorsen]

Your ingoing axle are worn to much.



How many teehts does your axle have? 11?

Rolf

[Muzz]

I was hoping to find something catastrophic but alas. The only question is, looking at this gear, there are some grooves, I don’t think this would cause a whine though :/

The grooves are standard; my Breva ones are the same.

Have no idea what they do.

[Rolf Halvorsen]

When the surface of the teeths are worn - it will bring noice.
The teeths surface of all the gear wheels should be smooth without errosion.
Rolf

[lucky phil]

Bearing in mind (pun intended) that I don't know all that much, and that my experience (little though it is) is with the later smallblocks (they are not so very different from the older ones), if you've whining in all gears, I'd guess that you'd better look at the components that are common to all gears. My 2014 V7 (only 115,000km) has now started whining in 5th gear, but I know that the hardening on the 5th gear dogs is flaking off - it wasn't whining when I had the gearbox apart - would have replaced them, but the price of one of the dogs was prohibitive, so I cleaning up everything, replaced most of the bearings in the gearbox & buttoned it back up. 4,000km later, the whine in 5th started. The gear changes did seem smoother afterwards, though. I also get a bit of whine in 1st and sometimes in 4th (I notice it now that I'm sensitive to it). I get no such whines in the 220,000km 2010 V7.

I would suspect a bearing, or more than one - they all revolve around the shafts, or the bearings or the bevels in the final drive, and it would be worth checking the drive shaft splines at the uni joint and at the final drive end. Good quality replacement bearings are available fairly cheaply from the bearing shops.

Hopefully, someone with more experience & a better idea of what's going on will weight in with pertinent advice. Try the smallblock forum on groups.io - there's likely a wealth of experience there waiting to be tapped. I shall be very interested in whatever you find. Keep us informed, please. And good luck.

Mal.

Do you mean "teeth". Wear of the engagement dogs won't cause whine.

Ciao 

[R1100purist]

I’m thinking about just putting it back together and running it. Although I still don’t know why I would get my oil dirty after only a few miles running. To be fair the transmission only has 6,000 KM on it so maybe it’s still wearing in?

To Rolf, yes it does have 11 teeth on it and I have a better photo now of the wear on 1st gear(??)

Lastly, I have a v7 breva box that I put on the V50 in the interim. Good news is it’s quiet! Bad news is first is way too tall and 5 is almost unusable. If I put my v50 gearbox’s primary drive from on the v7 box would this effectively lower my ratio? I think it would as the v50 is 14/23

[huub]

The breva box should be the improved one, recognizable with the small grub screw on the right side of the casing.
it should be quiter.
gear ratios between the boxes are virtually the same , the difference is made by the primary drive.
i i'm not sure  the primary gears interchange between the V7 and V50  gearboxes,

i would expect at least the clutch end to be different , ( the v7 box has a bigger diameter input shaft )
but as you already changed the gearboxes, i expect somebody has already been working on the gearbox. 

so anything is possible

[R1100purist]

So my V50 is a 1996 PA model so it has the later gen gearbox with the larger spline clutch input shaft. Just curious if anyone has tried such a swap.

[huub]

So my V50 is a 1996 PA model so it has the later gen gearbox with the larger spline clutch input shaft. Just curious if anyone has tried such a swap.

1996 has the later gearbox, i expected the V50 to be earlier

[lucky phil]

Someone with more experience than me will be along, but as I said before, some whine is normal. They are straight cut, after all.
(Thinly disguised bump to the top)

Yep. The gearbox behind my Centauro engine is noticeably "whinier" than the original V11 gearbox. Everything in it looks pristine, just gear manufacturing tolerances at work on straight cut gears. As an aside 2nd gear on my Focus RS has a little whiney period between 30 and 35kph off the throttle which I notice around the back streets sometimes. My first RS with identical gearbox didn't do this and both have helical gears. Same reason I guess. It's called individual character.

Ciao