Norton AMC gearbox 4th gear bushes

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p400

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I have read somewhere that the bushes 040062 in the (M4) main gear 040422 can be had in two lengths....and the longer bush are recommended.
I want to replace mine. Can anyone help on the part numbers, removal replacement procedures, and any special tools required?
I have not disassembled this gearbox yet, simply too much clearance felt on the mainshaft wiggle inside the solid feeling 4th gear.....leading to an out of round spinning clutch and a pulsing primary chain.
 

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Yea L.A.B. Beat me to it. The markIII's had longer bushes. But you can use three of the earlier shorter ones.
Thomas,
CNN
 
I went with 2 of the new longer ones so there would be a little oil retaining gap between them. There was an earlier thread on this topic. It also included a suggestion of scrolling the inside of those bushes to wind the gear oil into that area. That I didn't do.
 
Thanks guys for the info, I would like to know how difficult this bush remove and replace is going to be ?
Is hydraulic press required? special tools? Loctite? hammer and screwdriver? reamers?
I cant find previous thread please, where is it?
Thank you
 

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You can use a sized rod and a vice to press the old ones out, or if you take a hacksaw blade you can cut a groove along the length, once the groove is through the bush it will push out but you risk leaving a slot inside the gear for oil to leak. New ones will press in using the same sized rod and the vice. Depends on the bushes but assume they will need reaming.
 
Just get creative with some threaded rod or a really long bolt, some nuts, washers and a couple sockets the correct diameter.
You can press them in and out with such a contraption. My old bushings pressed in + out without any drama.
Here's pics from my Atlas sleeve gear but they're exactly the same. Bushings ordered from Old Britts did not require any reaming at all.
On the other hand my Commando bushings did require some reaming to fit on the shafts. I simply used a suitable sized deep socket wrapped with 800 grit emery
and polished the interior lightly until they fit perfectly.

Norton AMC gearbox 4th gear bushes


Norton AMC gearbox 4th gear bushes
 
Thanks Mark and all.
I pulled the gearbox down and found one of my issues.
The stock bushings in the 4th gear had migrated to the inside, leaving the clutch unsupported and wobbly.
Both bushes tapped out easily with the correct size socket, thank you.
 

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p400 said:
Thanks Mark and all.
I pulled the gearbox down and found one of my issues.
The stock bushings in the 4th gear had migrated to the inside, leaving the clutch unsupported and wobbly.
Both bushes tapped out easily with the correct size socket, thank you.

What would have caused that migration if the interference fit was correct and the bushes were assembled correctly?

I'm thinking its more likely assembly error?

If I recall correctly, I'm sure Norman Norman White told me he fits the small bushes and prefers them as it leaves space for and oil reservoir between them.

Can anyone confirm I am quoting Norman correctly and is this a view held by other knowledgable folk on here?
 
Fast Eddie said:
p400 said:
Thanks Mark and all.
I pulled the gearbox down and found one of my issues.
The stock bushings in the 4th gear had migrated to the inside, leaving the clutch unsupported and wobbly.
Both bushes tapped out easily with the correct size socket, thank you.

What would have caused that migration if the interference fit was correct and the bushes were assembled correctly?

I'm thinking its more likely assembly error?

If I recall correctly, I'm sure Norman Norman White told me he fits the small bushes and prefers them as it leaves space for and oil reservoir between them.

Can anyone confirm I am quoting Norman correctly and is this a view held by other knowledgable folk on here?

The normal way by many is fit the two longer type bushes one from each end. This will leave an eighth of inch space in middle to collect oil.

As the large loads of the transmission are applied to the bush it can be crushed and over time moves as a result. Think of it like pastry being rolled out with rolling pin eventually it loses the interference fit and starts to move. Locite on assembly may help and later style sleeve gears had circlips to stop bush walking out so the factory was aware of the problem.
 
If you install a washer on the mainshaft inboard of the clutch retaining circlip it will stop the bush moving outwards and getting chewed up by the circlip. No need for Loctite or similar if you do. See pic's.

Norton AMC gearbox 4th gear bushes
 
Has anyone used the Triumph long bushing? Instead of the traditional pair?
Available on eBay, listed with this number ..... 57-1370
It measures .813 x .910 x 2.585,
Seems to have an internal spiral groove to force oil back into the gearbox.
 

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P4oo,
You will need to machine the O.D. of this bearing to match the O.D. of the Norton bush in order to make it fit the sleeve gear. These are slightly larger. I am doing this on my P11 but I have not driven it yet to give you good data on the results. I also had a thread on this same bushing you bring up but nobody chimed in.
gearbox-modification-for-sleeve-gear-pinion-t20677.html
We are pilgrims in our progress which is a lonely path.
Cheers,
Thomas
CNN
 
CanukNortonNut said:
P4oo, You will need to machine the O.D. of this bearing to match the O.D. of the Norton bush in order to make it fit the sleeve gear. These are slightly larger. I am doing this on my P11 but I have not driven it yet to give you good data on the results. I also had a thread on this same bushing you bring up but nobody chimed in. gearbox-modification-for-sleeve-gear-pinion-t20677.html We are pilgrims in our progress which is a lonely path. Cheers, Thomas CNN

Does not appear to be any support gain with this hollow, long bush....so I will stick with 2 bush system. Thank you for the dimensional info.
 
I have found that a 1654 bearing is the call number for a 2.50" OD x 1.25"ID x 5/8"wide ball bearing that seems to sell for $5-10 on ebay..........but resold as Norton 404098 by the Norton parts suppliers for more money, as I would expect. This is the main gear ball bearing in the AMC gearbox.
Shown above as 040098 in the first post.
These bearing do not seem to be described with any engineering data that is useful, no matter who the supplier.
Japan, Britain, unknown, KYK, General, China, unbranded, Generic, Nice, etc......altho a premium price is offered for Genuine RHP.
What is the experience with non genuine bearings?
 

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That image is of a sealed bearing which is not required in the gearbox. Open best for lube. Maybe someone could fix it up for an outrigger bearing arrangement for support to the mainshaft a la Maney. My MK 111 gearbox has a roller main. And a roller lay.
 
I am seeing an upgrade for the layshaft bearing from 040100 ball to 067710 roller .
Please tell me about a roller up grade to the main gear bearing 040098, I don't find any info on this.
here is a layshaft roller found on ebay.

I found the oldbritts gearbox article, excellent
 

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There is, as far as I know, no such thing as a roller bearing upgrade for the output shaft bearing. Interestingly, my Quaife 4-speed wide ratio grasstrack gearbox has two very narrow ball bearings situated side-by-side instead of one big affair. It clearly works as it's taken years of abuse in my sprint-hillclimb racer, sustaining about double the power and torque produced by a Commando lump!
 
All very true ,there is no information on this roller mainshaft bearing. I had a buddy with a machine shop make a press-sleeve to enable the undersized roller to be fitted. Works well ,went in tight and does not move ,firmly in place. Remember the gearbox runs cool so no expansion concerns like in engine .
 
Isn't the standard ball bearing a good choice for the output shaft? I don't hear of many failures here.
Lot's of potential flexing going on there supporting the clutch, drive sprocket.
Would a roller bearing survive?

Also with a roller, wouldn't you have to shim the main shaft to keep it from moving.
 
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