Horrible noise from gearbox(?)

If it sounds like that it will show signs of wear, take the gearbox apart and inspect everything closely. Don't run it again or you may ruin those new gears. I would say it's in the box and you will be able to see something in there that will help. Chuck.
 
concours said:
"Bearings, bushes, or shafts are the only things I am aware that will whine. "

Gear teeth meshing whine. The whole reason helical cut gears were developed.
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Never had the pleasure of hearing the gears in an AMC gearbox whine. My bad for thinking they wouldn't be the source of the noise.
 
Schwany said:
Never had the pleasure of hearing the gears in an AMC gearbox whine. My bad for thinking they wouldn't be the source of the noise.
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The latest set I installed have a distinct 3rd gear whine, even above my damaged hearing threshold.

The finer points. Of the metal trades. Are lost, on most of what we get.
 
fiatfan said:
Well I´ve "thrown away" lots already, so.... An update on the gb oil, I was a bit tired and stressed yesterday, there´s no ATF in the box, I bought a Redline so that´s what´s in there. It´s blue, which I find slightly amusing....
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I can't remember if I ever tried Redline in my AMC gearbox. If I did it was Red. Didn't know they had Blue lube.

I used inexpensive 80-90wt gear oil. It seemed to work when the gearbox worked well.

Hope you figure it all out. Noise and vibration coming from the primary is not confidence inspiring while riding. That I know from irrelevant experience with an RGM belt clutch in a desert sled.
 
My only similar experience (RGM clutch basket aside) was when the primary cover worked loose and clattered against the Z plate under load, but since your motor is rigidly mounted it can't be that.
Just to be 100% clear, is the noise road speed related only? i.e. exactly the same regardless of which gear you're in?
If so, I can't readily think of anything inside the gearbox which would do this apart from an issue with the Mainshaft High Gear, which leads (as already said) to the final drive (clear chain run, no misalignment, rear sprocket secure etc.)...
What layshaft bearing are you running (apologies if you've already said)?
You haven't given much detail about the frame, and I'm curious!
No loose engine mounts/bolts, everything line up OK, good clearance everywhere?
 
fiatfan said:
I just suddenly came to think about the second gears that were changed sometime -73 or 74? Can it be a mix of gears, I´m not certain that I checked that.....
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Where did you get the gear cluster from? Do you know for sure it ran noiseless prior to the rebuild? As you say , NV changed the tooth profile on some gears, and the new gear wheels need to be installed as a pair, so please check that. 4th and countershaft gear also receive a new profile, if my memory serves me.
 
Piece of 18mm ply under centre stand ,start bike and put the tickover up to 2500 ? Put into gear and look round for the noise. Have someone's it on it to ensure it doesn't jump off the stand. They can also change the gears , rev up etc. Roy.
 
fiatfan said:
Well we have different views on money, I definitely don´t think a new gearbox is "relatively inexpensive". But never mind, so, the steel plate I took out was in the bottom, there was two on top of each other and the stack was too thick. Should have been clear on that. Many Norton owners use ATF oil, which they are very happy with, so I can´t see why I shouldn´t try?
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The yaki said:
Piece of 18mm ply under centre stand ,start bike and put the tickover up to 2500 ? Put into gear and look round for the noise. Have someone's it on it to ensure it doesn't jump off the stand. They can also change the gears , rev up etc. Roy.
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See post # 23 - he does not have a center stand .
 
If he doesn't have a center stand, borrow front and rear racing stands and try the yaki 's experiment
 
nortonmargie said:
If he doesn't have a center stand, borrow front and rear racing stands and try the yaki 's experiment
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Or even a bike scissor jack and some wood blocks. I like putting car jack stands under foot rests once lifted to stabilize everything.
 
Invest in one of these MC scissor jacks they are cheap under $100 and well worth every bit for lifting the wheels up off the ground and so stable to use, also works great on the lift table.
Horrible noise from gearbox(?)
Horrible noise from gearbox(?)
 
Didn't know that MC scizzor jacks existed! What a great idea! I need to get one- when I need to change the front tire (I pull the wheel off and take it to my friendly local modern motorcycle shop, who finds me a tire, installs it and gives me the wheel back) a scizzor jack will make it SO much easier!
 
nortonmargie said:
Didn't know that MC scizzor jacks existed! What a great idea! I need to get one- when I need to change the front tire (I pull the wheel off and take it to my friendly local modern motorcycle shop, who finds me a tire, installs it and gives me the wheel back) a scizzor jack will make it SO much easier!
Click to expand...
I wish I had mine 40 years ago, I paid $95au with free delivery too my front door, Chinese made is very strong and stable well worth the price and the best thing it sits under the bike out of the way with nothing sticking out the side of the bike the wind up handle is removeable and has adjusting arms to fit the frame rails or can be removed and just use the flat top.
Takes a few seconds to put under the bike and wind up great for chain maintenance or any wheel work, I have also used it for other jobs other than lifting bikes.

Ashley
 
Deets55 said:
FWIW, I had some bad results with Redline ShockProof gear lube. In my case it appeared as though the lube did not get between the bush and gear/shaft areas. Not saying it’s bad stuff, but it didn’t work for me.
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Ok, interesting, but I have had the internals of the box out twice and it looked like there was oil everywhere.
 
I'd speculate that it's more fundamental than oil choice...

Again, it may have already been covered, but not all Commando gears were the same throughout production, and they were certainly different to previous AMC gearboxes.
Identifying what you have might be challenging, but this may help. I seem to recall other data listing different ID marks stamped on the gears, but a brief search drew a blank.

S

Thread 'transmission variations'

There are a few changes that happened inside the box. I have a few gear sets and surplus gears. Is there anything written down about the different gears and how to spot them by number of teeth and measuring. I know a little bit about the AHB markings and the groove cut in the second gears as indicators. Some of these letter stampings are not clear.

I'd still like to know it the noise is purely road speed related or if it changes depending on what gear you're in?
 
fiatfan said:
Ok, interesting, but I have had the internals of the box out twice and it looked like there was oil everywhere.
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Understood. That’s why I didn’t criticize the product. I just threw my results out there in case they were helpful to someone else.
Hope you sort your problems out, speaking personally I know it’s really frustrating when I can’t figure out the source of something like that.
Pete
 
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