Jubilee late gearbox - only two gears selectable - fixed.

Dan, thanks for the suggestions, Yes I tried with the engine running and I checked the gear lever was not fouling on anything.

I am going to take off the gearbox cover without dismantling the clutch side to see if there is anything obvious as it is such a pain to strip the clutch side. I may still have to remove the clutch at some point.

There seems to be no further downward movement of the lever after second gear so it might be the selector is in the wrong place.

I'll give an update when I have some news.

Dennis

Dan, many thanks (again)! 

Not got around to taking the gearbox apart yet, enjoyed doing other things in the good weather. 

I have the manual as an .PDF but thanks for the images anyway.

The first thing I will check is the alignment of the foot-change ratchet alignment mark with the mark on the small pinion. If that is correct the other possibility is one of the 3rd or 4th gears may be reversed stopping the selector fork from engaging/moving the gear but I think this is unlikely.

Dennis

I found that the footchange selector ratchet was not aligned correctly with the small pinion on the selector shaft, hence the 'lost gears'.

The manual specifies aligning the mark on the selector with the mark on the pinion. Sounds easy but the first issue was identifying the mark on the selector as it is partly obscured by a locating plate and looked at first glance like a manufacturing blemish! Secondly, the pinion mark was in fact two punch marked 'N's, so I take it that the pinion tooth between the Ns is the locating one for neutral. If this was not obtuse, then not being able to see either mark on assembly was a real problem. The parts are behind the gear cover plate on assembly.

My solution was to find the position of the selector relative to the pinion without the cover plate in place, take the selector plate off without moving it, mark the two peaks of the pinion gear that mesh with the selector (those either side of gear trough marked by the Ns) using correction fluid ('liquid paper'), refit the selector and loosely fit the end plate, check the alignment by peering through a hole in the end plate using a torch to see if the mark on the selector is aligned between the marked teeth of the pinion.

Before I sound too smug, having  assembled fully the gearbox and I can now select four gears but there is a mysterious neutral beyond fourth gear and first is hard to select. I may  still be one tooth out on the small pinion !!

I will do a road test before I decide if I need another go at aligning the selector.

The manual seems light on advice.

I used to tell friends that Haynes manuals were similarly challenged. They follow an inverse law. You get 20 paragraphs on how to change a bulb and only a few lines for a difficult task usually starting with : "First remove the engine.....".

Dennis

Dan, many thanks. I am interested particularly in the alignment mark on the selector plate as I am still not convinced that what I am seeing is the correct mark. The pinion is marked clearly so identifying the position of the selector plate is critical to success. 

I have decided to strip the gearbox again to have one more go.

Dennis

Dan, I took some photos of the pinion and gear selector alignment marks. The selector plate mark is obscured by the locating plate so I have moved that to one side. The 'mark' appears to coincide with the hole in the selector plate. This mark is hidden when the locating plate is in position!

I am hoping you can confirm that you have the same alignment mark on your selector. 

Even if the alignment marks are correct there sees to be some potential on assembly to get the alignment wrong resulting in too few gears or at the other extreme, a false neutral after 4th gear.

Dennis

Dan, having just assembled my gearbox wrongly again I have had a eureka moment. I did not realise that  the selector alignment plate is detachable from the gear lever shaft!  I should have looked more closely at the diagram you posted.

No wonder I could not see the alignment marks. By disassembling the selector mechanism I should be able to offer up the selector and align it with the pinion before fitting the locator plate that obscured the alignment marks previously. This was not obvious before as the shaft (28 in the diagram) seems firmly fixed in the gear lever shaft (32). I will have to investigate how to get them apart.

Dennis

Dan,

Thanks anyway and good luck with your repairs.

Dennis

Dan,

After three more goes yesterday I might have set up the gear selector correctly.

As I suspected, fitting the selector shaft without the gear change ratchet does allow me to see the 'alignment' marks, the problem is that the pinion marks (the two N's) still only give an approximate alignment; one of three possible gear teeth. The alignment has to be exact otherwise the selector won't work properly. A single mark on the pinion would have been much better.

Frustratingly, you can only test the selector alignment with the gearbox assembled fully (without oil). If the alignment is wrong it is a full stripdown including mainshaft nut and tab washer.

It looks like the top 'N' mark, at about 4 o'clock, is the correct one to align with the selector mark, with the lower 'N' at about 5 'o clock.

No wonder I thought the selector shaft was part of the gear change assembly. I had to hold the gear change lever spline is a vice (lead jaw protectors) and drift the centre shaft out using a bolt screwed into where the gear indicator goes. The shaft has two o-rings as oil seals and they are a tight fit even when lubricated. This causes a problem on reassembly. When the selector shaft is in place in the gearbox the gear lever shaft has the fitted over it. I had to tap the gear lever shaft spline on the front face gently until the selector shaft protruded past the spline end; only then could I get the outer casing on.

Lastly, I found fitting the kick start return spring before fitting the clutch lifter and specifically the large circlip made fitting the spring easier as it does not foul the circlip. You might want to withdraw the clutch cable entirely from the casing as it can easily stop the inner plate going back in place.

Dennis

Dan,

Ouch, what a mess. I hope you locate a spare.

I now have four gears but the change is clunky. I used heavy grease to lubricate that gear selector shaft and that was a mistake. I thought it would help the two oil seal o-rings do their job but it just gummed up the shaft.  The shaft and seals do require lubrication but thin silicone grease might have been better.

Dennis

Dan, 

Any progress with the gearbox yet?

Planning to strip mine again in the next two weeks and I wondered how you got on.

Dennis

Dan,

Glad to hear that you are making progress despite some problems.

Bizarrely, I have TWO N's marked on the small pinion gear so you can understand why I have had problems. 

Your photo helps a lot as I can now make a good guess at which mark to line up with.

I am also wondering how good the selector locator in the base of the gearbox is (24 in the diagram you provided above)? It could be a weak spring or a worn pin, I have a new spring but I can't seem to find a new pin for sale.

Dan,

I have not tried Russel motors so thanks for that tip.

Also, I can't seem to identify a part number for the plunger (24 in your diagram above) in the NOC spares list.

There is a plunger on Ebay at the moment described as: "NOS camplate index plunger Norton Commando, AJS, Matchless, AMC, No# 04-0034."

Not sure if that would fit.

Dennis

Nick,

Thanks for both replies and the information.

Interestingly, the plunger listed in NOC spares for the Commando is '04-0034', most likely the same as Norvil's '040034' and it is only about a fiver!

Worth risking that to see if it fits.

Dennis

I have my Jubilee gearbox sorted at last.

Thanks to the NOC spares scheme I bought a new plunger spring and the other springs used in the gear change mechanism.

I was surprised to see that the old plunger spring was only two thirds the length of the new one and was much weaker. The spring that returns the gear lever to its central position was also worn and weak. 

The selector action is much tighter now though I still get a false neutral between 3rd and 4th gear but I can live with that.

As Dan suggested the plunger for the commando did not fit; it is the same size but is not chisel shaped at the business end. My old plunger was not too worn and the new spring made all the difference.

Dan's pictures helped me greatly to set the position of the gear change relative to the small pinion.

Dennis