Gearbox Killer

Ned · Jan 24, 2016

Here's some pics of what I found the other day when I opened my gearbox up to replace the kickershaft and seals.

Who ever had this apart before made a bit of a mess.

The main shaft nut has some slots in it from a screwdriver smashing it on and off.

Also every thread in the case is ruined as they have used the wrong pitch studs.

The box now is coming out to try and fix the threads and will also be gone through to see what else has been stuffed.

I'm hoping it doesn't get any worse.

Ned

fiatfan · Jan 25, 2016

That doesn´t look good, sorry for you. I have a similar problem with bad threads in the same place, but not as bad as yours. Time for helicoils or similar :wink:
Tommy

SteveBorland · Jan 25, 2016

I would be inclined to go looking on Flebay for replacement casings. Probably cheaper than helicoiling all the threads, quite apart form any other damage in the box.

OldForge · Jan 25, 2016

Heli-Coil & Time Sert kits are $20 to $60 & take about 2 minutes/hole to do right.
Replace the case w/a mystery item from E-Bay? Not really a good option.

kommando · Jan 25, 2016

Check the back of the case for cracks between the bearing housings, replace the shell if there are any. If no cracks keep the shell, get it helicoiled, doing them all is a lot cheaper per hole than doing one at an engineering place. If you pay using full beer cans or contributing cash to the Xmas party fund even cheaper

, paperwork is costly.

concours · Jan 25, 2016

OldForge said:
Heli-Coil & Time Sert kits are $20 to $60 & take about 2 minutes/hole to do right.
Replace the case w/a mystery item from E-Bay? Not really a good option.

+1
Disassemble, clean, inspect (don't fear the taint crack), repair threads and use it.

J. M. Leadbeater · Jan 25, 2016

I hear they look a LOT worse if you have ever had a non genuine Andover Norton gear lose an engaging dog while the box is in use!!!....Some idiots made gears leaving a sharp corner / stress raiser at the base of the engaging dogs enabling them to break off more easily......mind you they probably also used the wrong material to manufacture the gears to start with. A friends workshop used to have two such gears nailed up for his customers to notice so he could tell them who NOT to buy spares from......

ashman · Jan 25, 2016

Ned it looks a bit rough but it will be a easy fix, the gears and shafts look good, the main shaft nut just replace it with a new one and all good again, its just been undone and done up by someone that didn't have the right tools, the studs will be easy to fix by helicoil or timeserts and be good as new, no need to buy new cases, just pull it all apart and fix its properly, I have seen worst.

Ashley

fiatfan · Jan 25, 2016

My original 1970 box actually split horizontally once :shock: , luckily I was just driving around town doing maybe 20-25 MPH. I was slowly accelerating out of a junction, when all of a sudden there was one h-ll of a racket and I had no drive, so I looked down and behind me, and saw a long trail of oil...

. When taking the box apart it turned out there was an absolute sharp edge on the main shaft, where the diameter changes. No soft corner, dead sharp. That´s where it snapped right off. Glad I wasn´t doing 80 on the highway...
Tommy

grandpaul · Jan 25, 2016

How did such a rough-looking gearbox get into such a clean looking frame?

mschmitz57 · Jan 25, 2016

Yeah, This is all part of the process of making the bike "your own". It's a bitch discovering what some ham-fisted shop-monkey did to the bike in a previous life, but afterwards I find it extremely satisfying knowing I did the job right and that I brought it back from the brink. On the plus side the gears and shafts look to be OK. It's not that much work and It'll be better than new when you're finished.

Ned · Mar 18, 2016

Finally have my box sorted

The gearbox was completely torn down and inspected and as I thought it didn't get any better.

The cases ended up being replaced, was not worth fixing the threads as the bearing Journal was not up to scratch and was Flogged out.

Inner cover on inspection also had shonky threads and also one thread was missing some metal. Again not worth fixing so it was replaced.

The guts could of been worse but I still ended up replacing 1st and 2nd gear sets, the kick start shaft and of course all the bearings n bushs got renewed.

I also had the outer cover machined and fitted with a new seal.

The up side of all this is I now have a new gearbox.

Torontonian · Mar 18, 2016

Lots of damages. Roller layshaft bearing ?

Ned · Mar 18, 2016

Torontonian said:
Lots of damages. Roller layshaft bearing ?

Yes, Andover Norton sourced Part 067710.

Torontonian · Mar 18, 2016

Goodly.

CanukNortonNut · Mar 19, 2016

Ned
good job, That kick start shaft at the splines is what holds the crank from constantly loosening. Its false economy to buy a new crank and place it on something like the old one in your thread pics. Whats with the jumbled numbers on your gearbox outer cover shift indicator embossment.
Les Emery special? :lol:
Cheers,
Thomas
CNN

Ned · Mar 19, 2016

CanukNortonNut said:
Ned
good job, That kick start shaft at the splines is what holds the crank from constantly loosening. Its false economy to buy a new crank and place it on something like the old one in your thread pics. Whats with the jumbled numbers on your gearbox outer cover shift indicator embossment.
Les Emery special? :lol:
Cheers,
Thomas
CNN

At one point I'd say the shift indicator made lots of contact with that area.

I cleaned it up a little.

Gearbox Killer

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