Gearbox rebuild suggestions

I posted a recent update in my rebuild thread and the next item on the chopping block is the gearbox. My original gearbox was toast-apparently vast amounts of sand and no oil doesn't lubricate the gears very well. I need to take a three month break from the project for work overseas, but when I get back home I would like to start on that rebuild. My replacement gearbox is completely unknown to me, but I saw no visible issues upon disassembly. I'm looking for suggestions on what to check and what needs to be replaced-things like layshaft end float, seals, bearings, bushings, but especially known issues.

I replaced the kicker shaft o-ring first with a lipped "X" ring and finally with an automotive lipped seal. No more weepage after that. Inspection and possible replacement of the layshaft bearing should be on your list.

Typical items you need are on the gearbox rebuild kit. Look it up at Andover norton. Definitely replace layshaft bearing.

Roller Layshaft bearing and new sleeve gear bushes.

Some maybe helpful links

http://www.oldbritts.com/gearbox_a.html

https://www.accessnorton.com/NortonCommando/shimming-the-kicker-shaft.20856/

https://www.rgmnorton.co.uk

https://www.accessnorton.com/NortonCommando/yet-another-gearbox-rebuild-with-a-few-questions.19152/

Get Mick Hemmings DVD. Best resource tool in your toolbox.

Slick

First check to see if the gearcase has a crack between the two bearing bores, if not then:

Check the shafts for runout, check the gear for fit on the shafts, check the gear dogs for slight undercut and no rounded edges. check the k/s pawl for wear long with the inner side of the gear that it drives. Replace gears in pairs.

The suggestions above are good; the AN kit has all the seals and gaskets and 3 bushings, it also includes the 3 springs. When all parts are clean place the shift shaft between the inner and outer cover with nothing else and check for excessive radial play; these 2 bushings are not included and you need to be very careful if you need to replace the bush in the outer cover.

Before reassembly make sure the gasket surfaces are as near surgically clean as you can get them and that the alignment pins will accept the cover meant for them without any forceful persuasion, they should fit by hand, but need to be fit "square"

I fit the fully populated layshaft with k/s shaft, use a new gasket (buy two) or consider that the compressed gasket is about .010" and fit with out. At this point you can check and set layshaft end play.

Fitting the shift forks can be difficult. I use a large Philips screwdriver that I put in from the drive side to hold the forks onto the camplate, then push it out with the fork shaft, piece of cake.

Best.

I'm in the middle of an incredibly slow moving gearbox overhaul right now. The layshaft bearing (the smaller of the two that rides in the case) is a known weak spot. With an unknown history I suggest changing all three bearings as it can be very difficult to identify a weak ball bearing. There are several bushings but the ones that seem to take a lot of wear are in the sleeve bearing. There are two but there's room to fit three. Beyond that you'll want to make a very close inspection for wear on the gear teeth, the engaging dogs, and of course measure your shaft diameters, hoping they are within the bounds of being serviceable. I am going to feed my box a new shifter spring (not the right name, but it's the part that returns your shift lever to 'center'). It's important to get it set up very well. The Old Britts write up with photos is very helpful. My shifter pawl shows a bit of wear. I've got it on back order and don't mind waiting for a new one to arrive.
Before you head overseas, I would consider ordering all gaskets, bearings, bushings and seals. The only items that might not be needed are some of the bushings and having these parts on hand will help you move through your rebuild fairly quickly upon your return. Best of Luck with it!!!

Check the kickstart shaft in the kick pawl area for cracks.

Besides what's already stated

- Do not remove the camplate. It is a real pain to get timed right when you put it back
- If you do, brace the quadrant with something across the studs when you unscrew the camplate bolt. Otherwise if the quadrant moves to the top of the gearbox when you loosen the camplate bolt and it will only be engaged by one tooth and that tooth will certainly brake if the camplate bolt is at all tight.
- Replace all rubber components
- Shimming the kickstarter less the .01 is too tight IMO

Good luck

TomU said:

Besides what's already stated

- Do not remove the camplate. It is a real pain to get timed right when you put it back
-

Good luck

Click to expand...

Nothing has changed.
Loose fit the quadrant and cam plate, shift the quadrant arm up to the stud as per the workshop manual.
Fit the detent plunger until it only just engages the cam plate (so it can rotate easily)

Fit the inner cover, shift to 1st, shift to 4th, its all but go, no go in the cover slotted window top and bottom.
As posted elsewhere the short end of a Allen key can be used in the cam plate hole for addressing the two external bolts for the cam and quadrant which do not need to be that tight and can get a spot of blue Loctite at the thread area under the washer if need be.

I would suggest (even though a pain working away) stripping the box and hand brass bristle wire brushing all of the internal components, kerosene washed and dried then all examined and trial fit.
The gear pairs and dogs can then be accessed for any replacement parts, AN is a 8 day parts delivery.
Any used cluster will have some varying form of wear on the tooth contact area's.

Being non circlip shafts, its a walk in the park.
I would only replace bushes if absolutely needed and feel modern bronze is not like that of 50 years ago.

TomU said:

Shimming the kickstarter less the .01 is too tight IMO

Click to expand...

If you were referring to my post I said, only, that a compressed inner cover gasket would add about .010 to the layshaft/k-s end play, for those individuals that choose to measure end play without the gasket in place. I like an end play in the mid 20 thousands knowing that GB will "grow" a bit an add to whatever end play was selected. No end play is not good, too much is worse. If you are seeking a finite number then read all the posts on the subject (lots) then load the opinionated numbers into a Standard Deviation calculation...

Best.

Referring to Old Britts. They recommend .005 in

ludwig said:

Check the kickstart shaft in the kick pawl area for cracks.

Click to expand...

I would only like to add to ludwig's comments about the Kick start shaft, which he suggested to check in this area. Also if the kick-start crank is persistently loose, and no amount of tightening keeps it tight, then the splines on the shaft are badly worn. Even if you purchase a new crank it will eventually get hogged out in short order just like the old one. Buy these two items as a set. I would recommend the MkIII type crank as it give more clearance for the pea-shooter muffler from getting scuffed. I Recommend that you stick with AN original parts here. Some of the Pattern cranks have different spline groove patterns so beware.

Regarding bronze bushes:
I would recommend using the MkIII bushes at the sleeve gear: 2 are required. These are longer than early types and don't tend to move or spin within the bore of the sleeve gear. A new 1st gear lay-shaft bush recommended as these tend to crumble, and look for worn dog holes on this gear.
2nd and 3rd bushes don't tend to wear too much but if it make you happy for peace of mind ... have at it and add to your shopping list.

A new kick start pawl is recommended.
Try using X-ring "O-rings" for the outer cover.
Purchase a set of gearbox gaskets from JS motorsport. these are silicone gaskets for a leak proof box.
The lay-shaft bearing has been covered above. two types: The Mick Hemmings type Ball bearing or the Superblend type: 06.77105 (NJ203E TVP2.C3).

YMMV
Cheers,
Tom

CanukNortonNut said:

I would recommend using the MkIII bushes at the sleeve gear:

Click to expand...

Due to the different wear patterns, you may need to replace the mainshaft if you replace earlier bushes with the later ones.

TomU said:

Due to the different wear patterns, you may need to replace the mainshaft if you replace earlier bushes with the later ones.

Click to expand...

TomU,
No I don't think so IMHO.
Have you done this Mod???? If so, Have you had problems with this Mod????
In my experience, it will fill more of the center of the 4th sleeve gear bore with less air gap and more bearing surface area. It will have enough of an oil channel still remaining providing you push each bushing in from both ends. I have done this on a quite a few gearboxes for Pre MkIII Commandos. So I don't know where you are coming from? Putting a main shaft on a set of V blocks and a dial indicator on a surface plate would quickly tell you if your shaft is bent.
If you use AN, Original bushings, these should not require any reaming what so ever. It should be a slide fit once fitted as Mick Hemmings would say. Another trick is to use 3 shorter Pre MkIII bushings in the bore.
Cheers,
Tom