Atlas Gearbox

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Feb 22, 2006
G'Day Everyone,

Could someone tell me if there is any discernable difference between an Atlas or a Commando Gearbox.

Regards Mike.
I think ( from distant memories ) it's just the layshaft length. They have a different clutch.
Someone will be more certain than me, but I have a couple here in Brissie if you want to have a look or measure up. They are for the AMC type clutch.
That would depend to a certain extent on which year of Commando gearbox you would be comparing the Atlas gearbox to?

The early 750 Commando and Atlas boxes share many internal parts according to the parts books, but changes were made to the gears at various times. The later boxes have stronger gears and stronger gearbox castings. The 2nd gear ratio also changed on the 850. The mainshaft is different between the Commando and earlier models because of the different clutch I believe.

The 850 Mk III boxes are obviously different due to the L/H gear-change mechanism.

The top mounting lug on a Commando box is slightly narrower than the Atlas (Dominator) one I think.
The reason I am asking is there is one on e- bay for sale advetised as a Commando g'box but when you read the fine print it says it's from an Atlas

I believe the Atlas/Dominator casing has a different positioning for the mounting holes as well as the other differences mentioned.
My Commando uses a 56 Dommie box and as Les says, the top mount is wider than Commando. Basically the top and bottom mountings are the same width and the Commando top bolt spacer is not used as the box slips right between the plates perfectly. (does anyone know why Norton did this?)
You will also find the outer cover may have the clutch entry further back (anticlock) than Commando meaning a more difficult route for the cable behind the ISO tube. I replaced my covers with used Commando parts.
All the gears are interchangeable in any AMC box, only the mainshaft is Commando specific. I just replaced my 1st and 4th gearsets with current parts. Gearing between 1960-1973 is same as Commando when the 2nd set got a higher ratio.
the Commando top bolt spacer is not used as the box slips right between the plates perfectly. (does anyone know why Norton did this?)
The Commando box is slightly narrower to allow the use of the spacer.
By removing the spacer you can rotate the box (after removing the lower engine bolts) and remove the box with engine cradle and engine still in the frame. With the earlier box, this is possible, but difficult to move the top of the box with the top engine mount bolt in.

Dave M. The mounting for the G15/N15/P11 hybrids are different from featherbed/Commando's to allow for the transmission to be placed closer to the engine, but all featherbed and Commando models have the same mounts, except for the narrower top mount on the Commando
Thanks for that info Ron L, I bought a case on E-bay that was described as a Dominator box and which had different mounting positions. If I'd have known it was for a P11 I would have kept it and built one of those beauties around it!
I have a buddy that built a featherbed cafe racer using the G15/N15 primary and transmission. Made his own mounting plates from aluminum. It really turned out nice. Moving the transmission closer to the engine allowed a small battery box to be mounted behind the transmission. The G15/N15 and P11 primary cases (Matchless) are some of the prettiest. The down side is assuring proper rotor/stator clearance, as the stator mounts in the outer cover and it is impossible to measure the installed clearance.

I have seen a couple hybrids smoking from the primary due to rotor/stator contact.
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