To grind or not to grind...that is the question

I got the gearbox apart, looks pretty good, some things nice, some not so. Second main is the only one showing any geartooth wear. Took the gears and shafts to work and used the microscope to examine. So, here is a couple of questions on which I would greatly appreciate feedback.

1) A couple of dogs show mushrooming on corners - like 30-40 mils of displacement from a crisp corner. Do you grind it off or leave it? (If i grind it off will I screw up the hardening of the rest of the gear.)
2) The layshaft bearing on the left side doesn't not slide on and off easily, I assume a little scotchbrite scrub is ok to clean up the shaft ?

I am new to digging into a transmission, reading alot and studying videos(all your old posts are extremely helpful when I search, folks on this forum are great), I am learning a lot, just don't want to make a "you did WHAT?" kind of decision.

thanks in advance.

I only know down and dirty AMC gear box servicing. Found the cause of my dog face smearing to be worn bushes shifting alignments. Found my cause of bush wearing was excessive throttle too long too often in lower gears. I dressed mine and worked fine after new bushes reamed. There's a simple sugar solution way to re-harden that may be worth the effort. None of my layshaft end bushes slipped on/off w/o some heat and tapping to seat. Enough so made me pensive each time, [4] that I'd fully seated. May not be normal Norton, just Commando common with me - but so far so goodie. Get 2 first cog bushes as first to go away.

Hi Hobot, my shaft bushes are pretty messed up, and lots of brass chips in what was left of the gear oil, i was wondering if the PO ran in low gears alot, your comment of too long too low rings a bell. 1st lay bush is a press fit, but mine spins loose, is that not good?

and the kick bush that fits inside the kick shaft slips in and out, is that one supposed to be loose like that?

No none of that is good.
1st gear bush is a press fit as well as the kick shaft bush.
There are other bushes which are supposed to spin in the gears, floating bushes. Those tend to freeze up.
You need to go complete rebuild of the bearing and bushes.
Your luck the gears are ok as the will set you back a pretty penny, or quid, yen, whatever.
Some of the wear on the dogs can be clean up with a Dremel tool without ruining the hardness.

and the kick bush that fits inside the kick shaft slips in and out, is that one supposed to be loose like that?

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Ugh is easier to type than -Oh No for you, but just flash on the grins gotten by DPO, I do. Only takes one over tight 1' chain to accelerate bush destruction too. The kicker bush is usually a real bear to get out, special pullers or grinding to cut it out, like in my case. In for a penny down for pounds and pounding. Soup to nuts AMC time and more learning Cdo curve balls. Keep the old sleeve bushes as spacer between 2 new bushes and not a bad ID to oil groove em as no oil can get in while in lower gears. Simple as AMC boxes are they can be tricky first couple times through. I don't think its critical the bush is bang on tight, but might put in boiling water to see if they hug each other better or worser. Possible shaft bent form the fun factor and floppy supports helping to wallow it. What's is a more serious issue is if the bearing bores are wallowed loose. 4 solutions I'd read, new shell, intensive repair process, set screws/stakes or JBWeld. Spend for or barrow the newer gear box video and call us when thing don't follow the script. I've been through the gear box blues and it was hard on me to get pass them, knowing I'll face em again someday if I continue to enjoy my Combat, even sanely as can't avoid lower gears too long to get to terra firma .

Thx for replies. I have vids, books, etc. Sometimes just like to ask some questions to get grounded and avoid the "you did WHAT?" response. Hobot, I will play with bearings and shafts i think I get the extra bearing bit. However, can you please elaborate on the oil channel bit on the sleeve bearings? I assume you mean to scribe a groove 5 mils or so deep and 10 - 20 mils wide in a spiral on the non-shaft side of the bearings with a dremel grinder tool. i have not gotten pressed in bearings yet, I see holes in them, not sure about grooves. Thx, Hobot.

Bushings are not called bearings . Just took apart my gearbox to find wear to the mainshaft sleeve gear bushings. Will be tapping in one new followed by a worn old one to act as a spacer then followed by a new third. The first gear bush layshaft looks like it was drifting and one end is ragged. Im going to change that one too with new. My question is could the worn sleevegear bushes allow oil to enter the primary ( new belt drive with pushrod seal kit ) . It's either that or my crankseal is going.

Oil groove 3 sleeve bushes in a spiral, but stop just short of the outer edge of the first one in, ie: where it can and will leak out of the gear box, either on sprocker or into primary. It don't come with a seal nor really needs one the factory found because it don't even get enough oil up- in there to oil itself when spun above oil level. Groove goes on bush ID against the center shaft as that's where it gets most force least oil and greatest heating when engaged. Don't worry your belt can be run in oil bath it ya like and likely not see any oil from gb as long as not over filling over the tops of lowest gears seen down in inspection hole. I broke my own rule this spring and had a mess out drive sprocket that oiled drive chain about as good and disiplined exerpts reccomend and csaued such grinding paste it ate up half chain life in a couple weeks as oil reached natural level. Chain adjustment is holding again now dry as a bone but now rides too tall in valley to sustain teeth life if I kept up on my max out to find out runs this month.

Let us know if dressing the dogs and renewing bush and bearing support is enough to get sweet shifts again. Curious how easy the old bearings drop out with or w/o heat and reinstall and stay put. This may give insight on the lay shaft bearing being beat a sloppy fit. If ya can bump out the bearings when just warm to touch likely not stable in the long run.

The kicker bush is really note worthy news-mystery how it could bet worn on its outside dia. as mine are all fixed tight to that only inner shaft turns in it. If new bush here just slips in-out then I'd use JBW and foregetabout it. I oil grooved this too, just in case, to delay next time.

Guido said:

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There are other bushes which are supposed to spin in the gears, floating bushes. Those tend to freeze up.

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G'day Guido
I recently rebuilt my box, including replacement of the bushed gears. The floating bushes threw me into a flat spin at first, because the original gears had pressed in bushes.
I couldn't get any advice from the supplier, so the job was held up for a while until I just got on with it and realised that the bushes are captive when assembled onto the shaft.
I second your dismay at the 1st gear and kickstart inner bushes being loose:- must make kickstarting a bit iffy.
My layshaft 1st gear was good so I just replaced the bush (pressed in) as recommended to square up the gear for kickstarting, also replaced the pawl of course.
Cheers Martin

Torontonian said:

Bushings are not called bearings

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..Indeed, my mistake, thank you for correction. These posts can lose some value when one has to figure out what someone meant, not what they said.

actually, a bushing seems to a type of bearing

from wikipedia:

bushing (plural bushings)

(mechanical engineering) A type of bearing, a cylindrical lining designed to reduce friction and wear inside a hole, often used as a casing for a shaft, pin or hinge.

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I suppose seeing as a bushing takes a load it is a type of bearing.

Ok, first try at photos, so this is the layshaft.

I intend to reuse all the parts (gears, etc.) except re-bush the whole thing (three bushes), and replace the left side bearing - parts on order. Any comments? I have the vids, and books, but I would like one of you helpful folks to render opinion if you care, because I don't know a lot more than what I read about what to look for - I have no experience in this.

Again, this was a basket case non-runner when I got it, but not really very worn out. Who knows.

Fig 1: The total group. Please note the bluing of the shafts, is this a concern? The shafts are straight as far as i can tell (I used a steel straight edge.)


Some close ups next.

Fig. 2: First lay gear - don't know if you can see well, but the outer edge of the bearing is totally chewed up, kick teeth inner look good, however. The bush spins free, but both ends are mushroomed and the bearing will not slide out, even though it is loose. I got to get it out and inspect inner surface of the gear.


Fig. 3: Kicker bush (right end on layshaft), turns loose and free in kick shaft, and layshaft turn looser and free in this bearing. This bearing but does not show free play in the kick shaft, just can spin like the kick shaft inner diameter is a mil or two less than the kicker bush outer diameter, if that makes sense. The outer diameter of the kick bush shown is 0.873 - 0.875" on the main body that slides into the kick shaft - my calipers to measure ID are not long enough to reach into the ID of the kick shaft. The surface shown is next to the 1st lay bearing (above photo.)


Also, that left hand side bearing (original I think, imprinted S P, Portugal, ROL, 6203) was stuck to shaft and will not slide on now (heated it up to get it off.) Took heat to get it out the the case, case looks ok. Of course, I took the picture with the left bearing on the right side of the photo. (convention being left is to drivers left, right is to drivers right, at least that is the way folks restoring Austin Healey's do it.)

This is an example why you all are so helpful - most decisions are random without the benefit of experience.

Third gear bearing nice and tight, not chewed up at all.

Kick shaft has one lost tooth outer spline, one lost tooth inner spline. I intend to reuse it.

Gear tooth faces not hardly worn at all, however, second main pretty pitted. Photos of main shaft later.

Again, thanks for help.

Gear tooth faces not hardly worn at all, however, second main pretty pitted. Photos of main shaft later.

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The non rolling element bearing bushes are the weakest links in AMC gear boxes for a few reasons and should be what's thought about when thinking about lube, not the cog teeth, which essentially only rot away by corrosion. Teeth don't hardly wear on faces to matter only break off if over powering them in drag sprints, which no amount of perfect lube can help.

The first cog bush can even break up and fall out. Wearing thin can allow jumping out of 1st when going slow the instant engine + coating loads match, to release drag ya might be expecting to hold turning aim.

I want to know how tight your new kicker bush fits. Mine have all be rather tight to hardly get all the way in and then needed reaming for the internal shaft.

Glad to get some reviewing on this as got to assemble a gearbox for my special this year. So far last one in my Combat has lasted since '05.

Hey Hobot, If you like I can send you my kicker shaft and the new bush when I get it before I put it in if you want to inspect it in person, just send the parts back when you are done. Or any other stuff you want to see. It would be a $6 thing to mail it, I bet, no skin off my nose to do that. I am in no rush. Only about 110F+ here, no reason to worry about riding a bike until weather gets good in October or November...

Hobot, I will send you the old one too, if you take it up. I also want to observe the difference.

Its hair dryer blasting to ride here too and not in a heat wave. I'm confused, I don't want more clutter of used up parts. Just I've never heard of kicker bush loose on its OD so just want to know if your new bush is normal Snug fit again, as a clue to the wear being on the brass bush or the steel shaft. My next build has a brand new bright chrome or nickle coated kicker shaft so expect a task to get bush seated. if your new one just slips in its not a good thing.

LOL Hobot, just offering to let you see it in person, no problem if you don't want to. Pretty cheap to send to you and have you send it back by the mail.

Sometimes I prefer to just take your word for it. Your annoying offer does bring up a sideline issue with Commandos hobby. What to do with used items, either for someone's future use or just your own flash backs. Also is it still just a hobby when it consumes most of ones attention? I never think about this when on a fully fettered Cdo, but do on first hint of its next issue.

Oh yeah, I don't use no stinking gaskets in my AMC's no more.