Broken Tooth Gearbox

[duncan4000]

So managed to snap another gear. Yes the second in 32000km.....never had gearbox issues with anything else I've ever owned.

Mechanic is recommended to replace gears that also mesh with broken one. Unfortunately it appears triumph only sell this as a whole kit. T1183700

Thoughts on just not replacing this bit. Not currently broken. Or alternatively can you buy each seperate and it's just not shown on triumph

 

[Vector]

What model bike?

 

[duncan4000]

What model bike?

2017 triumph bobber

 

[atomsplitter]

Sounds like something Triumph needs to investigate with some hardware failure analysis. Try and get Triumph involved with this repair. I'm curious what they will say since I have three Bonneville engined bikes.

 

[sikatri]

Definitely something to inquire about! How did it happen and how did you notice it?

 

[duncan4000]

Failure went from running perfect to the gearbox jamming up. Pulled over and managed to get gear changing again. But eventually jammed up again. Turned out it was the tooth had fallen down and jammed in the gear change mechanism.

Had the gears inspected. Impurities and cracking on nearly all of the gears. The gears are cast. So being brittle impurities and cracks are highly likely.

Failure appears to be a stress fracture. Caused over time and most likely started at one of the impurities in the cast iron

Examples of some of the impurities and cracks shown below.

 

[Vector]

Darn thing should last more that 7-8 years.

 

[sikatri]

Darn thing should last more that 7-8 years.

I agree, don’t know exactly what to think. OP have you had any conversation with Triumph over this? I’d be interested to know what they say. Your OP mentioned another broken gear. This has happened before? Are there third party performance parts to replace these components? Seems like you have it all apart, I would be looking at building it new with components that are geared for high performance. Perhaps they’ll be less likely to break.

 

[duncan4000]

I agree, don’t know exactly what to think. OP have you had any conversation with Triumph over this? I’d be interested to know what they say. Your OP mentioned another broken gear. This has happened before? Are there third party performance parts to replace these components? Seems like you have it all apart, I would be looking at building it new with components that are geared for high performance. Perhaps they’ll be less likely to break.

Had a look. Can't find aftermarket options

Yeah it happened at 18,000km just before warranty ended. They replaced it that time. That was second gear. Similar failure pattern.

This time 3rd gear at about 32,000 KMs.

My first message to triumph about this was met with an unlikely to do anything about it. But that was before I diagnosed the exact issue. I'll be drafting up another email with a better case shortly

If I had to guess I think the gear selector shaft contributed to the failure. Both times it was extremely worn. I could see this jamming up on gear changes putting extra stress and load on the gearbox

 

[sikatri]

Keep us posted.