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Rebuild gearbox fail


wimpus

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Hi, 

I again rebuilded a failed gearbox for my Spitfire 1500

Now 2000kms later.. 

Yesterday drove onto the main road.. bang!

And prop banging..

 

Stopped on the side of the road, making noises in all gears, needed a pull to home  😔.

 

Today took the gearbox out.

Clutch like new, opened up the box.. ffs..

Tooth missing on the laygear and input damaged.

 

This gearbox did fail before.

Also laygear(mostly shaft failed) and took everything with it.

So now it had:

-new NOS laygear

-new input

-new OD mainshaft

-new japaneese gearbox bearings etc.

 

Now the latest bang it made.. what could caused it ? 🤔🤔😔

 

It was all very smooth exept gear changes (suspected the syncro's)

 

Ps.. truelly hate Spitfire gearboxes now, had them fail lots of times now.

20220502_091311.jpg

20220502_092508.jpg

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Dont forget Wimpus that sometimes fails can just be bad luck and a new components break from manufacturing defects.  In industry theres a 'bathtub' curve produced for failures where proportionally more occur at the beginning, then there tends to be a quiet period before the failures increase again as the equipment wears out....

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Oh dear….. how very upsetting 🙁Were all the gears from the same set or have you mixed parts?

Even if all the same set, new bearings means that the gears will be meshing slightly differently, applying forces to the teeth differently? This can cause noise (which sometimes improves after a period of running) or, rarely, if you are unlucky, sudden breakage. Seems you are unlucky ☹️
 

Have to agree with you on Triumph gearboxes….. (though 1500 single rail not normally the most troublesome). Getting hard to find parts in good condition.

Nick

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In all my recent searching for gearbox parts (3 rail 4 synchro but there is some crossover with the single rail parts wise) I saw no trace of anything new new rather than NOS when it comes to gear sets and input shafts. I’ve seen at least one gearbox rebuilder ad where there’s an extra, high, surcharge if the laygear is unserviceable too. So I don’t think anything of that sort is currently being remanufactured.

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When I lost some teeth off the third gear of the cluster in my Vitesse gearbox Mike Papworth suppied a NOS third gear but the cluster had had the needle roller bearing area bored out and sleeved. He told me there had been cracks for a while as the broken area was partially bright and partially stained.

Regards

Paul.

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4 hours ago, Josef said:

In all my recent searching for gearbox parts (3 rail 4 synchro but there is some crossover with the single rail parts wise) I saw no trace of anything new new rather than NOS when it comes to gear sets and input shafts. I’ve seen at least one gearbox rebuilder ad where there’s an extra, high, surcharge if the laygear is unserviceable too. So I don’t think anything of that sort is currently being remanufactured.

Bastuck are offering laygears which presumibly are new as theres no mention of exchange or reconditioned...

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The other thing that can be a factor in that particular spot is whether the spigot bush in the back of the crankshaft is a) present and b) in decent condition as it plays an important supporting role in keeping everything in line.

Nick

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3 hours ago, johny said:

Bastuck are offering laygears which presumibly are new as theres no mention of exchange or reconditioned...

If the problems someone on here had with the dimensions of one of Bastucks new mainshafts are anything to go by I wouldnt be very optimistic about their gears! 

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3 hours ago, johny said:

If the problems someone on here had with the dimensions of one of Bastucks new mainshafts are anything to go by I wouldnt be very optimistic about their gears! 

Oh, do you have a link to that? Just out of interest as to what was wrong! I’ve just used a Bastuck mainshaft (via Canley’s) myself. While I didn’t go over the shaft itself with a micrometer, everything fitted on it fine and I was able to build up the gearset to acceptable tolerances. 

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8 hours ago, johny said:

Here you go and the worst bit was Bastucks response....

Oh. Great. Well that’s a nice quandary now. Do I yoink it back out the car and strip the whole thing back down to check the shaft. I read through three different manuals, including the reprint of the factory one, and nowhere did it mention measuring the bush to shaft clearance. Though presumably cause Triumph could rely on their own parts being the right size…

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I think theres a good chance the previous shaft was a rogue one as, because of the small production quantities, they are probably made one by one on a conventional lathe rather than some computer controlled automatic thing. Then, if quality control is poor, out of spec components can slip through but hopefully this is just an occasional occurance.

A similar problem has been reported with oil pumps for our engines where different internal clearances result in some pumps giving lower output pressure...   

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On 07/05/2022 at 14:40, Nick Jones said:

Oh dear….. how very upsetting 🙁Were all the gears from the same set or have you mixed parts?

Even if all the same set, new bearings means that the gears will be meshing slightly differently, applying forces to the teeth differently? This can cause noise (which sometimes improves after a period of running) or, rarely, if you are unlucky, sudden breakage. Seems you are unlucky ☹️
 

Have to agree with you on Triumph gearboxes….. (though 1500 single rail not normally the most troublesome). Getting hard to find parts in good condition.

Nick

Input, laygear and 1 gear where changed to used or in the case of laygear.. NOS.

This was a very silent box,

But didnt want to go into gear good (mostly 3rd).

As you mention the crankshaft bush, all new as I renewed everything on my new engine.

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On 09/05/2022 at 08:08, johny said:

Here you go and the worst bit was Bastucks response....

Well.. i bought a new mainshaft for the box that failed now.

It was really tight.. 

But with only 1 working hand its a bit hard 😅

 

Time to get it apart, do know a sourcebfor nos mainshafts now.

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is it O/D or non OD shaft, I have a single rail original non overdrive main shaft spare from a J type conversion i did, your welcome to it gratis, it looks in good condition i'd have to check postage from Aus and time for delivery. If wanted can supply photos.

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On 13/05/2022 at 05:50, wimpus said:

Input, laygear and 1 gear where changed to used or in the case of laygear.. NOS.

This was a very silent box,

But didnt want to go into gear good (mostly 3rd).

As you mention the crankshaft bush, all new as I renewed everything on my new engine.

So the part that failed was NOS and previously unused…… That is REALLY irritating!

Any evidence of anything that might have got caught between the gears and caused the break? Broken circlip under 3rd gear?

Nick

 

 

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8 hours ago, Nick Jones said:

So the part that failed was NOS and previously unused…… That is REALLY irritating!

Any evidence of anything that might have got caught between the gears and caused the break? Broken circlip under 3rd gear?

Nick

 

 

Need to take it apart fullt 

Sadly with my recent angle grinder accident its hard to get it apart with only 1 fully working hand 😔

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depends on evolution of  clutch /input shaft    there seems there are two   mentioned in the Moss if converting from 6.5 to 7" clutch 

so its tied in with cut spline and rolled spline shafts must have different spigot diameter 

sorry all a bit vague but to have so many input failures we are looking for something obscure  like its unsupported correctly  just a thought 

Pete

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I see Rimmers have the same part number for many small chassis Triumphs but others for Dolomite 1850/Sprint (including a needle roller type) so maybe these could be used by mistake and not support the input correctly... 

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