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Gearbox clutch spacer

Submitted by ron_tomkins on Sat, 06/04/2019
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Heavy Twins

Looked at every illustration that I can lay my hands on and can't establish what I need. Can someone please give me some information about the gap between the end of the gearbox mainshaft and the back of the clutch drive sprocket. It appears that a tubular spacer should slide over the splined shaft and pass through the inner primary chaincase to locate the clutch assembly in its correct location on the shaft. Any guidance to what spacer I need will be much appreciated.

Regards Ron.

56 Dominator 99.

Submitted by robert_tuck on Sat, 06/04/2019

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Hi Ron,  On the later 99 twins the clutch center (actually the spider) locates on the shaft and a shoulder in the spider abuts the end of the spline.  Sometimes the shoulder is a poor one and the clutch can migrate a bit up the splines and the back of the spider can grind on the end of the sleeve gear ,this does not help the gearchange . If anyone has this issue look inside  a few spiders ,and you will see what I mean.If its been migrating it will be a BUGG-----R-. to get off.

Thanks for the quick response Robert but I think that we may be at odds. My clutch body slides on and off of the splines with no problem, I am just at a loss as to how the distance between the back of the clutch body and the gearbox end of the shaft is filled. It would seem that a tubular spacer is required to make up the space and form a "seal" where the shaft passes through the inner primary chaincase. I just cannot find any information about any spacer.

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Submitted by robert_tuck on Sat, 06/04/2019

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I felt sure the end of the sleeve gear passes through the primary case sliding disc and very nearly meets up with the back of the spider ( and sometimes does ). Don't remember any spacer. Going to look at my books now!!. Later--- Do you have a bit of a mongrel there ?, or an earlier box not AMC?.

My 56 Dominator was fitted with the laydown gearbox from new and I have just rebuilt the box so I know that the sleeve gear is located correctly. As you can see in the picture: with the clutch body in position, up against its shoulder there is a good 12mm of splined gearbox mainshaft  still visible. There has to be a tubular spacer or perhaps I have the wrong clutch basket? To clarify, please note that the splined boss protruding from the clutch back plate only protrudes by 2mm and its O.D. is too big to pass through the inner primary chaincase. 

Any advice most welcome.

Submitted by ian_soady on Sun, 07/04/2019

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On my ES2 with laydown gearbox the clutch centre just slides onto the splines till they become shallower. Not an ideal situation but seems to work OK.

However, it does look as though your primary chaincase isn't going far enough towards the gearbox. The clearance between the rear chain and the back of the chaincase is normally pretty minimal and you look to have a lot of clearance there.

Morning Ian, appreciate your input. Without modifying the inner chain case mounting brackets there is no way that the gap can be reduced, also the alignment of the chain case would be at odds with the engine, frame and gearbox. There is no possibility to move the gearbox closer to the inner chain case so I am stuck with the gap. Can you tell me if your clutch centre passes through the inner chain case, through the felt washer seal? If not, what does pass through the felt washer seal?

Submitted by ron_tomkins on Sun, 07/04/2019

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After another couple of hours in the shed I am none the wiser. With the clutch body locked onto the main shaft the drive sprockets are perfectly aligned. The gap between the back of the clutch body and shoulder of the main shaft is 15mm. The inner primary chaincase occupies a part of that space. Surely there must be a tubular spacer, possibly having a splined bore to suit the mainshaft,  15mm long with an O.D to suit the felt seal of the inner chaincase. I can't believe that I have a totally unique set up.

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Hi Ron, no spacer at this place. Looks like your sleeve gear have been cut. Felt washer seals on this gear. Have yet seen that on a box used on tracks, so lightened wherever it was possible.

Thank you Benoir, this sounds like progress. Are you saying that my sleeve gear should be 15mm longer, and pass through the felt seal to mate with the end of clutch centre? There is no evidence of the sleeve gear having been shortened but it would explain why the gap is there. I strongly suspect that I will be making a tubular spacer to resolve my problem.

Thank you again for your valuable input.

 

Submitted by philip_ham on Sun, 07/04/2019

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Ron, sounds very puzzling.  I've never used a sleeve behind the clutch on my 1955 ES2 with a Laydown box.  The only place I believe the felt seal fits is in the footrest tube that has a funneled end.

Is this the original gearbox from the machine?  I'm told there is a difference in the length of the gearbox main shaft for a single and the twin, but my Spare Parts books for a 1955 ES2 and a 1955 Model 7 both quote the same part number i.e. D12/324.

Phil.

Thanks Robert. Is there any chance that you could clarify your statement. If the spacer is not tight after the clutch nut is done up it will be free to spin on the main shaft and its only purpose would be to close the gap where the shaft passes through the the felt seal in the inner chain case.

Thanks again. Ron.

Submitted by robert_tuck on Mon, 08/04/2019

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The sleeve gear (on my later box) has an extended nose that pokes through the primary case sealing disk.This gets very close to the back of the clutch spider,(a few thou) .The gearbox mainshaft turns within the sleeve gear at different rates depending on what gear you are in.For some reason your box does not have this feature(been machined off for racing?), you intend to fill the gap with a spacer which may work as well as the original (and poor) design did.Because the clutch(spider) and sleeve gear turn at different speeds (except when in top (direct gear) they do not want to be grinding on each other, They will do this if your spacer is too long or if the clutch spider shoulder is poor and allows the clutch to migrate a bit up the shaft.(mine did!). Some think it should not make much difference in theory. In practise it does. which is probably why someone has machined yours off and used an open primary A LA MANX??.The spacer could be sealed to the mainshaft with some silicon ,it does not want to turn on it (wear) ,but needs to be removable to allow a gearbox strip. A new sleeve gear would be best though. I am not familiar with the earlier box so may be talking bo llox !!!.

Submitted by alan_rogers on Mon, 08/04/2019

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From memory of my model 7 isn't there a lip on the centre clutch drum that locks the drum between the main shaft and main shaft nut.

Great information Robert, I really appreciate it. I will look into finding a new/unmodified sleeve gear but for expediency I will give the siliconised spacer a whirl.

Thanks again Ron.

Nothing wrong with your memory Alan. There is a shoulder/lip on the splined bore that should locate the drum however, the shoulder is subject to wear and, over time, the drum can move closer to the main shaft nut.

Many thanks for your interest. Ron.

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Submitted by richard_tool on Mon, 08/04/2019

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Hi Ron  - 

Here is a shot of my 56 Model 99 gearbox which I believe to be all original. Perhaps this will help you determine whether your sleeve gear has been altered.99 sleeve gear

Submitted by richard_tool on Mon, 08/04/2019

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I can measure this distance from mainshaft/input spline ends to end of sleeve gear/output accurately with dial calipers if needed if you want to turn up a spacer - LMK .

Hope this helps - Richard

Submitted by ron_tomkins on Mon, 08/04/2019

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Everything is now crystal clear, many thanks. Thanks to a previous owner having shortened the sleeve gear, it is now obvious that I have been trying to find a component that never existed. As stated earlier, I will turn up a sleeve for a quick fix and source an original sleeve gear through the normal channels

Can't thank you all enough for solving my mystery. Best regards Ron.

 

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As a further aid to the spacer equation I came up with .775 " from shoulder to end of sleeve gear -  this taken with mainshaft pushed in to take up any slackShoulder to sleeve gear dimension

Submitted by benoit_lesage on Tue, 09/04/2019

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Hi Ron, I thought the sleeve gear was shortened but I found a sleeve gear from a laydown gearbox, left on the picture, AMC on the right. Laydown one is shorter and no area for a seal. It seems you have wrong parts in your AMC box. Maybe at least sleeve gear and 3rd mainshaft gear 'cause even if teeth number is identical, dogs are not exactly the same size.

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Hi Benoit, thanks for the pictures. We seem to have got a bit confused, my box is a laydown box not an AMC box. On that basis it would appear that I have the right sleeve gear for the box but we go back to the initial question of how do I obtain a seal through the inner chaincase?

Regards Ron.

Submitted by ian_soady on Tue, 09/04/2019

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.... on mine (plunger ES2), just a gaping hole. But by some magic it doesn't seem to lose any oil there.

Submitted by robert_tuck on Tue, 09/04/2019

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When I was attempting to achieve the "holy grail" of a no leak case I gunned a circle of bath mastic on the innercase behind the clutch ,I "veed" it to throw any oil away from the shaft .oil is thrown up by the chain and runs down the back of the case. It worked. Its still there many years later and the case is pretty leakproof now.

 


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