MKIII cross shaft primary to gearbox alignment

Hi all,

I have been restoring an MKIII Commando over the past several months. I couldn't have come as far as I have without the knowledge people have shared through this incredible forum. But for the first time I have come across an issue I can't seem to find information on, and was hoping for some help. To start things off I have an MKIII (Dec '74 manufacture) that I have stripped down almost completely to clean and inspect parts, replace all the oil seals and questionable bearings, etc.

Well I finally got my primary assembly put back together this weekend only to discover that my primary case and gearbox are fairly out of alignment, causing the cross shaft to take on an uncomfortable looking skew. But it seems like the distance between the gearbox and engine is pretty fixed. I've tried slacking the drive chain and loosening all the bolts at the gearbox cradle to see if I can wiggle the gearbox and/or cradle forward a bit, but it doesn't seem to have much affect. The gearbox, cradle, and engine are all original to the bike.

Has anyone encountered this issue before? I have attached some pictures of the situation. Any help would really be appreciated, and if I've left out any important information I'll be glad to clarify or answer any questions.

Thank you,
Anthony

Anvill said:

Well I finally got my primary assembly put back together this weekend only to discover that my primary case and gearbox are fairly out of alignment, causing the cross shaft to take on an uncomfortable looking skew.

Click to expand...

Yes, that's normal (if you remove the cross-shaft and fit it in the outer cover bush then it should rest at the same angle) so it should all fit together.
The ratchet mechanism in the Mk3 gearbox outer cover is also skewed and why the Mk3 has the 'spherical' knuckle pin roller instead of the pre-Mk3 cylindrical roller.

The cross shaft is angled to miss the clutch drum and its mentioned in the workshop manual.
This fact even eluded TTI (the New Zealand gearbox manufacturers) I ordered an extra heavy duty 5 speed box as a direct replacement for the box in the Mk3 that will have the Merlin engine fitted. Yes we can make that for you, they said. A few months later the well packed gearbox arrived and as soon as i got it out the packing i noticed that the gearchange shaft (that exits the inner cover to connect with the cross shaft) was parallel to the mainshaft and was far too long. In no way was this box a direct replacement for the Mk3 box.
The reply to my emails to TTI were quite frankly just excuses.
The following is the reply i received.

email from TTI
'To date we have sold around 15 Mk3 commando gearboxes with the left foot change. In talking with Bruce and the other designers here there has only ever been one instance of an issue. That was an issue with the spline length, which we shortened by 10mm. All other gearboxes that we have sold have had no reports of issues come time to install.



Bruce had a look at the photos you sent and said that he had never seen a Mk3 Commando gearbox with the angled shaft like yours.



I think there is going to be some research undertaken to see if there are different models of the Mk3 gearbox as there may be a rare model or two out there that are different to the one our left change mechanism was modelled off.'



TTI eventually supplied me with a short gearbox shaft that i was able to fit with a Hooke Joint that i cut the splines in so was able to use a standard length cross shaft.
TTI never admitted they had made a mistake, in fact they didn't believe me that the Mk3 had an angled gearchange shaft until they had inspected a Mk3 box. They did offer a full refund on return of the box.
TTi's solution to the cross shaft misalignment was to cut the spline undersize so the connector sleeve was able to cockle over just enough to allow the (extended) cross shaft to enter it. A very poor solution, frankly a bodge of the worst order as the splines would have just point contact and will wear rapidly leading to a shit gearchange.
One wonders if any of the 15 Mk3 commando TTi boxes with the lefthand change are actually fitted/used? Or just garage queens?
The rest of the box looks well engineered.

" Often wrong, NEVER in doubt!"

Glen

L.A.B. said:

Yes, that's normal (if you remove the cross-shaft and fit it in the outer cover bush then it should rest at the same angle) so it should all fit together.
The ratchet mechanism in the Mk3 gearbox outer cover is also skewed and why the Mk3 has the 'spherical' knuckle pin roller instead of the pre-Mk3 cylindrical roller.

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That makes a lot of sense when you break it down. Those assumptions get me sometimes . Thanks for this information, I was able to get things mostly put back together today instead of spending the afternoon scratching my head and dismantling things further. Its always a nice surprise when a problem isn't actually a problem! Although sorry to hear the reverse was true for the 5 speed.

Anvill said:

Hi all,

I have been restoring an MKIII Commando over the past several months. I couldn't have come as far as I have without the knowledge people have shared through this incredible forum. But for the first time I have come across an issue I can't seem to find information on, and was hoping for some help. To start things off I have an MKIII (Dec '74 manufacture) that I have stripped down almost completely to clean and inspect parts, replace all the oil seals and questionable bearings, etc.

Well I finally got my primary assembly put back together this weekend only to discover that my primary case and gearbox are fairly out of alignment, causing the cross shaft to take on an uncomfortable looking skew. But it seems like the distance between the gearbox and engine is pretty fixed. I've tried slacking the drive chain and loosening all the bolts at the gearbox cradle to see if I can wiggle the gearbox and/or cradle forward a bit, but it doesn't seem to have much affect. The gearbox, cradle, and engine are all original to the bike.

Has anyone encountered this issue before? I have attached some pictures of the situation. Any help would really be appreciated, and if I've left out any important information I'll be glad to clarify or answer any questions.

Thank you,
Anthony

Click to expand...

hi Anthony,

I just discovered the same angled crossover shaft on my 1975 Mk3. First I believed something is terribly wrong with my bike and was searching the net to find some clues on this issue. Thankfully I found your post. So, apparently it seems to be according to design. But I believe there are complications to the gear changing due to this strange engineering solution:
The crossover shaft bushing in the primary cover seems to sit in a slight angle to accomodate for the angled shaft. However, the shaft coming in from the gearchange pedal appears to be straight. Now, how do the gears on the gearchange shaft and crossover shaft mesh together in a smooth way with this misalignment? I noticed that the gear on the crossover shaft (part no. 06-6181) is only kept in place by a circlip and has quite a lot of play. Maybe this is to enable some kind of "self-alignment"?

Before I became aware of the "angle issue", I tried to eliminate excessive play in all this gearchange mess by glueing the gear on the crossover shaft in place with Loctite. But since then I found the gearchange to be stiff and notchy. Maybe the excessive play is necesary to allow the gears to engage properly, as said above... I think I will remove the glue and see what happens.

I feel the gearchange only has two alternatives: "sloppy but somehow working" or "stiff and notchy". It's frustrating.

On your bike, do you also find lot of play on the crossover shaft gear? And how is your gearchange?

Jan

Jan Huss said:

However, the shaft coming in from the gearchange pedal appears to be straight.

Click to expand...

No, it is also angled.


Replacing the cross-shaft, outer cover cross-shaft bush and cross-shaft connector (5) should reduce the play but probably won't eliminate it completely.

Jan Huss said:

hi Anthony,

I just discovered the same angled crossover shaft on my 1975 Mk3. First I believed something is terribly wrong with my bike and was searching the net to find some clues on this issue. Thankfully I found your post. So, apparently it seems to be according to design. But I believe there are complications to the gear changing due to this strange engineering solution:
The crossover shaft bushing in the primary cover seems to sit in a slight angle to accomodate for the angled shaft. However, the shaft coming in from the gearchange pedal appears to be straight. Now, how do the gears on the gearchange shaft and crossover shaft mesh together in a smooth way with this misalignment? I noticed that the gear on the crossover shaft (part no. 06-6181) is only kept in place by a circlip and has quite a lot of play. Maybe this is to enable some kind of "self-alignment"?

Before I became aware of the "angle issue", I tried to eliminate excessive play in all this gearchange mess by glueing the gear on the crossover shaft in place with Loctite. But since then I found the gearchange to be stiff and notchy. Maybe the excessive play is necesary to allow the gears to engage properly, as said above... I think I will remove the glue and see what happens.

I feel the gearchange only has two alternatives: "sloppy but somehow working" or "stiff and notchy". It's frustrating.

On your bike, do you also find lot of play on the crossover shaft gear? And how is your gearchange?

Jan

Click to expand...

I'm glad you found the post helpful Jan. LAB has you answer about the angle. I have lots of play at the cross shaft as well, in particular the coupler between the cross shaft and gearbox, which seems like more of a universal joint than a rigid connection. I think tolerances in this assembly are probably supposed to be somewhat loose since the distance between the gearbox and engine (as the mounting point for the primary case) probably varies from bike to bike. You can loosen all the bolts mounting the gearbox and perhaps move it around a bit in relation to the engine, but gauging the direction or degree to move it to accommodate for a more rigid cross shaft assembly is beyond my comprehension. In the end I determined that since it wasn't a constantly rotating part, the slop was probably (somewhat) intended and acceptable. But folks who have had their Nortons way longer than I would certainly know better.

My hope is to remove and replace the bushing on the outer primary cover since it's the wear item in the assembly. But I wasn't able to get the bushing out via a heat gun and drifting it with a socket. I'll probably try boiling some water under it next--that worked well for removing my seized rear wheel lock ring. The rest of the assembly I am planning to keep as is unless the gears actually start slipping. Having no experience with one in better condition its certainly sometimes hard to tell on this bike what's wear and what's not!

Anthony

Anvill said:

My hope is to remove and replace the bushing on the outer primary cover since it's the wear item in the assembly. But I wasn't able to get the bushing out via a heat gun and drifting it with a socket.

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If I remember correctly, I cut a thread in the cross-shaft bush and extracted it with a long bolt and something like a socket used as a slide hammer.

L.A.B. said:

If I remember correctly, I cut a thread in the cross-shaft bush and extracted it with a long bolt and something like a socket used as a slide hammer.

Click to expand...

Excellent idea!