75 Commando, stuck in 2nd gear - help

Hello - My 75 Norton Commando 850 was working beautifully yesterday until a mile from home, I got stuck in second gear. I was able to get home but now I am left with a faulted gearbox. Does anyone have any advice they can give on this matter?

Thanks in advance!

Hi, welcome. How much can you do? Have any Whitworth wrenches? Have you been in the trans before? In the engine? In the primary? Any other symptoms first? Did it shift perfectly before? Who/when was the last one in the trans? Pull the trans outer cover off for a look...

Get your tools out and steal some time to open up to see what spills out or take out of cradle to take apart and list the new parts to order then as manual states, just do the process in revers till rolling again.

marinacom said:

I got stuck in second gear.

Click to expand...

If it happened suddenly then the ratchet pawl spring (04-0038) may have broken, as the gearbox would then be stuck in whichever gear it was in when it broke.

http://www.oldbritts.com/nor_mk3_75_7.html

http://www.oldbritts.com/1975_g7.html [18]

http://www.oldbritts.com/gearbox_a.html

Another possibility would be that some part of the cross-over shaft mechanism has failed?

http://www.oldbritts.com/nor_mk3_75_11.html

Pawl spring does not have to break or even look bad to loose its alignment clearance to allow pawl to swing in to next gear. I've had 2 events of no shifting joy d/t pawl springs, one had rusted to point it lost its springness and another that looked good and seemed to align fine but i just couldn't get it right - till a new one diddled at bit, exactly as the bad one - then worked for ever more. The frustrating thing on this 2nd spring was it was working fine till opened outer cover just to reseal my KS and never touched that part at all, yet until figured out and replaced I was stuck at home on my own. Next common thing I've had cause trouble in 1st and 2nd shifts was the 1st gear bush thinned to breaking up allowing mis alignment to engage and disengage 2nd. I've had other worn bushes allow cogs to tip on shaft so wore down-distorted the dog lever faces, sort of like a beaten on chisel end curls back on itself. Grinder on dog faces and new bushes solved it long term. In this instant case who knows until gone through but may be as simple as just main shaft end nut backed off some.

If the box didn't seize with a bang and there are no other symptoms then the pawl spring is my guess too. Nice and easy to change (although a bit more work on the Mk3 as the rear master cylinder is in the way). I carry a spare spring under the seat.

A spring under the seat, dang, not a bad id i will have to do as gotten pretty darn far on current spring, which only mean that must less time before you know what.
Trick to adjusting it, as none i've gotton worked right out the box, is to get the section of the legs the pawl swings by parallel and just enough space pawl swings clear - so ignore the manual distance to shoot for - or may be fussing and cussing again because that last fine tuning un-paralleled the legs - uhg. If pawl sweeps past spring legs in both directions freely then likely not a pawl spring issue, ugh.
I clear spray paint the parts above oil level or tends to rust up. Grease might work too as no oil gets there to wash off.

hobot said:

A spring under the seat, dang, not a bad id i will have to do as gotten pretty darn far on current spring, which only mean that must less time before you know what.
Trick to adjusting it, as none i've gotton worked right out the box, is to get the section of the legs the pawl swings by parallel and just enough space pawl swings clear - so ignore the manual distance to shoot for - or may be fussing and cussing again because that last fine tuning un-paralleled the legs - uhg. If pawl sweeps past spring legs in both directions freely then likely not a pawl spring issue, ugh.
I clear spray paint the parts above oil level or tends to rust up. Grease might work too as no oil gets there to wash off.

Click to expand...

I'd vote for the pawl spring, it's in the outer cover, so it's not too bad to get at. One of the legs on mine popped out of the groove. I believe I had a choice of first or second gear, though.

-Eric