Layshaft and Mainshaft Woes!

Hi folks,
I’ve stripped down my gearbox to see what horrors hide in there and was not disappointed with my findings.
Every bush was falling to bits. From the attached pictures you can see the wear that has caused on the shafts.
The markings are light and can barely be felt with the finger nail test. Are they safe to put back in as is or do they need replacing?
Or alternatively can they be resurfaced?

Strangely, the gears do not have any signs of wear on them. Could this damage be the result of a lack of lubricant perhaps?

If there is any sign of blueing they have been overheated but otherwise I would polish them up and use them, they look good to me.

Hello Davo,

Looks like there has been a lack of oil on those parts. But as he last guy said, try giving the area a rub over with 400 grit to see if the blue is only on the surface.
I have just done a box up and replaced all the gear and shaft bushes. Also check the kickstart case bushes in thwe case, there are quite a few bushes involved in the layshaft and little here and there add up. Glad to here the teeth on the gears looks good.

Cheers Richard

RGM sells a nice gearbox rebuild kit with all the needed parts.
050107 GEARBOX O/HAUL KIT, COMPRISING OF SLEEVE GEAR BEARING,SLEEVE GEAR OIL SEAL,L/SHAFT SUPERBLEND BEARING,M/SHAFT BEARING,SLEEVE GEAR BUSHES,L/SHAFT 3RD BUSH,L/SHAFT 1ST BUSH,L/SHAFT SUPPORT BUSH,M/SHAFT 2ND BUSH,GASKETS,'O' RINGS & SPRINGS AMC TO PRE 1964
£ 108.00

Thanks for the replies, I can sleep easy now.
An RGM overhaul kit is about to be ordered.

Cheers

Dave

Check out RGM for other goodies, they have a Norton script inspection cover, folding kick lever, belt primary................. Ohh the money that could be spent!

Since you're down this far, I would take the 2 shafts and chuck them up in a lathe with a dial indicator and check the runout.

Since you're down this far, it would be a good idea to take the 2 shafts and chuck them up in a lathe with a dial indicator to check the runout.

This is an innate-built in feature of AMC gear boxes that have been rev'd up in lower gears, a bit more than required in mostly straight-open race tracts, and is d/t to the spinning parts both throwing out cooling lube and preventing any to get back in while being reved hi outside of 4th. There IS No solution - only some relief by ATF-thin lube, after you have new bushes reamed to fit the cleaned up shaft surfaces. Save one of the old sleeve bushes to put in middle of 2 new end bushes to keep them apart nearer their load bearing jobs. Of course not enough lube to start with can aggravate in normal race or street use.

I have had shafts bent by over tight primary and too loose a final chain that rode up outside of rear sprocket and can tell ya they do not bend like a walking cane handle but like a antelope horn in a cork screw manner and takes unwinding to get mostly back to straight.

In Ozarks twisting contests it takes 30-45 min of constant lower gear use just short of blowing motor rpms to come out ahead. I look at AMC bushes now like a tire or speedo drive, not enduring friction parts like clutch or brakes.

Thanks hobot,
it all makes sense now.
You know once upon a time a scene like the one below frightened me. My Commando restoration has cured me of all fears knowing I may be devling deep into it's internals again in the future.
And yes Roger is slowly becoming the major beneficiary of my meagre wealth!

Oh gosh my davo, I too flat fogged out on just seeing the procedures and parts displayed in the manual, flipped through that fast as could thinking no way am I up for that level involvement. Ugh, now rest of life just don't seem as complex or tough to handle anymore.

Take good look at the sleeve shaft/bushes and then at how oil can get into it unless sitting still. IF running much in lower gears, especially in anger, highly suggest Dextron II ATF.

There is no need of any gaskets in AMC gearbox, in fact better w/o them as tends to relieve need to shim the kicker/lay shaft slack, more rigid assembly and no waiting on vendor to get going again. Oh yeah nicer fit in cradle too.

I found best lube level is just covering cogs as viewed via inspection hole. OK a hard hot run Peel showed me her happy level by no longer drooling into clutch.

Cam plate and lever with knuckle index right when knuckle is closest to cover edge yet covers still close.

I may try drilling the sleeve shaft cogs and bushes to let more lube in to carry off more heat, but ain't sure if it'd just let what little is there right out faster. ugh. Steve Manning on real racing Manx reports same sleeve area foul up d/t high rpm in low gears, so it ain't Cdo torque and power hurting this, just no oil flow.