Triumph pre unit gearbox

baz

baz

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Does anyone have first hand experience of what fits what on a pre unit gearbox
IE will the unit outer and inner cover fit the pre unit?
The box I have has the inner and outer case shortened
So no kickstart
 
No. Unfortunately not.

There's two options, the slick-shift and the standard shift. The slick-shift internal mechanism can be removed and used as a standard, but only the pre-unit inner and outer covers will fit on the case, not unit.
 
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t ingermanson said:
No. Unfortunately not.

There's two options, the slick-shift and the standard shift. The slick-shift internal mechanism can be removed and used as a standard, but only the pre-unit inner and outer covers will fit on the case, not unit.
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I thought so but wasn’t sure, so didn’t comment.

But what I do know is, some parts that reside the inner cover, like the gear change quadrant and plungers, are also different for the 5 speed. Annoyingly, 4 speed parts DO fit… they just don’t quite work right… giving missed changes and false neutrals. Yes, I found out the ‘practical’ way !
 
Fast Eddie said:
I thought so but wasn’t sure, so didn’t comment.

But what I do know is, some parts that reside the inner cover, like the gear change quadrant and plungers, are also different for the 5 speed. Annoyingly, 4 speed parts DO fit… they just don’t quite work right… giving missed changes and false neutrals. Yes, I found out the ‘practical’ way !
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Yes. Very true as well. The Triumph 'box has enough neutrals as is. There are some thick gaskets out there that cause a scenario that turns every shift into a new false neutral. Make sure you put it back together with none, or very thin ones.

If you need a new inner cover, make sure the threads are good on the cable adjuster boss. Often times those are stripped out. It's a fine thread (that I don't think exists elsewhere in aluminum), and I found it cheaper to get a new cover than the odd size helicoil kit that you'll only use once.

The entire 5 speed gear set can go into a pre-unit case with a bit of work, but it does have to be the whole kit and kaboodle. The early 5 speeds were a bit fragile, but have probably removed themselves from eligibility by now.
 
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When set up right, using the right parts, that are not worn out, a 5 speed Triumph box (it’s a Quaife design after all) is sweet and precise. So if it’s not, there’s something not right.

But when mixing and matching components that have come from a 50 year plus time span, that were never actually designed to be put together, some trial and error, and patience with the setting up, will most likely be required.

The last 4 to 5 speed I did was in my ‘68 T120. That was a new Harris cluster, and quadrant, and plungers. That went together easy and is as sweet as. And it really compliments the light crank 650 motor well !
 
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The pre unit box I have has a nourish splined main shaft
So a commando clutch fits straight on
It was built around the early 2000s by Phil Pick at triple cycles I believe
But the box has been cut for racing
So no kickstart
 
Fast Eddie said:
I thought so but wasn’t sure, so didn’t comment.

But what I do know is, some parts that reside the inner cover, like the gear change quadrant and plungers, are also different for the 5 speed. Annoyingly, 4 speed parts DO fit… they just don’t quite work right… giving missed changes and false neutrals. Yes, I found out the ‘practical’ way !
Click to expand...
I once saw a slick shift outer cover on a heavily modified trident/ R3 hence my question
It's a long time since I played with unit and pre unit triumph stuff and I can't remember the difference in the components
 
Perhaps it was a hacksaw pre unit?

You also some times see unit covers on a pre unit… but that’s when it has a NRE gearbox shell.

The NRE shell was bomb proof, and clever. It had Norton mounting points and took 5 speed Triumph internals and covers.

Hens teeth today though.
 
I know of one fitted to a trident ;) (But why? :( )
Triumph pre unit gearbox
 
Fast Eddie said:
Perhaps it was a hacksaw pre unit?

You also some times see unit covers on a pre unit… but that’s when it has a NRE gearbox shell.

The NRE shell was bomb proof, and clever. It had Norton mounting points and took 5 speed Triumph internals and covers.

Hens teeth today though.
Click to expand...
I'm considering welding ribs to the gearbox case
But I'm not going racing with it so probably unnecessary
I'm going to weld up the mount holes/slots and re machine them on my commando gearbox cradle
As for the kickstart I don't ever use it so I could do without
But it'd be nice to have as backup
 
Yes I could see ribs helping stiffen things up.
Provided the welding doesn’t distort things ?
 
Baz I have a cut back case on a unit box, nicely done, with a kevlar/fibreglass end plate. Gives you more room in the frame/ footrest area.
I will have a look in my Triton boxes & see if I have any spare pre unit gearboxes/shells/cover/bits lol & swap you. Still have my vintage sidecar to build so wont need a kickstart in the platform.
 
Chris said:
Baz I have a cut back case on a unit box, nicely done, with a kevlar/fibreglass end plate. Gives you more room in the frame/ footrest area.
I will have a look in my Triton boxes & see if I have any spare pre unit gearboxes/shells/cover/bits lol & swap you. Still have my vintage sidecar to build so wont need a kickstart in the platform.
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https://www.ebay.co.uk/itm/20421725...gGXShiHQWK&var=&widget_ver=artemis&media=COPY this is what I bought
The outer and inner look extremely well modified
I'll possibly/probably run it as is initially
I will modify the top and bottom mount to put the output shaft exactly where the amc one was
But I would like to have the kickstart as an option at some stage
 
t ingermanson said:
That does look really nice. Hope it's as clean on the inside for you.
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Found time to take the outer cover off this evening
It's a very clean conversion
 

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I’d your box was built for racing by Mr Pick it’ll most likely have his semi close ratio conversion and will be a really sweet box.

As you have an electric leg, my advice would be to leave it be and fit it as is.
 
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