Gear Identification

Hi all,
I am rebuilding a Norton Commando gearbox, and the gears have no identity stamps such as AH etc, save the sleeve gear, which has 6 stamped on it.
I have seen this on other gears, anyone know its origin?
The unmarked gears look in pretty good condition, a little wear on the teeth but nothing major.
TIA

The only gear I've seen marked with a '6' is the later layshaft 4th.

Strange thing that "6". I have never found a layshaft 4th gear without it except a new one I bought from AN that had AH. I have at least 6 of them today from 141xxx to 325xxx gearboxes. I've seen a couple of sleeve gears with a 6 but sleeve gears seem to be changed more often than layshaft 4th gears.

I had a discussion with Ashley at AN a while back and he was unaware of the 6. He expected AH or nothing. I remember reading about AH and 6 some time ago but can't find it now. If I remember right, it was saying not to mix AH and 6 but I can find no reason not to. The AH lay 4th gear I bought measured exactly the same width, major tooth diameter, and minor tooth diameter and the seemed to run exactly the same in the gearbox. the only difference I could see was that the leading edge of each tooth was sharper on the AH than 6 but that could be that it was brand new.

It gets more confusing with 2nd gear AHA and AHB and it's easy to make a mistake if you have 2nd gears laying around. The main shaft and layshaft 2nd gears do not mix and match..

Your avatar looks like it may be a MK 111 . Important .
At some point in later production both 2 nd . gears were changed to help pass new noise laws .
These gears must be changed in sets if so .
Perhaps LAB has stats on this .
The 6 I've not seen .

Torontonian said:

At some point in later production both 2 nd . gears were changed to help pass new noise laws .
These gears must be changed in sets if so .
Perhaps LAB has stats on this .

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First fitted to the 850 Mk1A and then MK2, Mk2A and MK3. These gears are marked AHB and have a groove in the dog.

marshg246 said:

I remember reading about AH and 6 some time ago but can't find it now. If I remember right, it was saying not to mix AH and 6 but I can find no reason not to.

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AH and 6 can be mixed but not with the early Commando sleeve gear.
Apparently, the tooth form of the Commando 4th gear pair was modified from serial 128646 (INOA Tech. Digest).
This seems to tie-in with the '68-'70 parts book, as both 4th gear part numbers changed for 1969.

The third gear pair were also changed slightly later.

Be aware that it is possible that a LS 4th marked 6 could also measure two different major diameters, 2.00'' and 2.050'' Some of the early AMC LS 4th gears were apparently marked with a 6 and to confuse matters later with a 9. The larger gear is the version usually found in Commando gearboxes as Greg has found.

Madnorton said:

Be aware that it is possible that a LS 4th marked 6 could also measure two different major diameters, 2.00'' and 2.050'' Some of the early AMC LS 4th gears were apparently marked with a 6 and to confuse matters later with a 9. The larger gear is the version usually found in Commando gearboxes as Greg has found.

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The presence of a "6" was the common way AMC indicated a minor revision where no visual alteration was apparent. I have no knowledge of a "9" marking elsewhere - this is probably a "6" stamped upside down. If the marking "6" coincides with "AH" , as stated in #6, it seems unlikely the gears were manufactured with different major diameters! AMC had a modern gear cutting facility.

I remember having read that John Favill - the transmission specialist with NV - worked with AMC on the early Commando gearboxes and that some gear pairs were changed wrt. tooth form. Your finding suggests it was the 4th gear set and this is backed by the change in part numbers for 1969 (06.1057 & 06.1058) as mentioned by Les . This would necessitate a "6" on the LS gear as well as the sleeve gear. Finding gears with these markings in bikes with high serial numbers (rather than gears marked "AH") just means someone has swapped gears at some point in time.

- Knut