Triumph pre unit transmission

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Joined: Tue Jul 03, 2018 3:06 pm

Triumph pre unit transmission

Unread post by Montij » Sat Jul 14, 2018 9:12 pm

Can anyone tell me anything about this transmission?

Im hoping to rebuild it but dont know exactly what i have.
I think the front cover may be incorrect cant find any pictures online of one just like this.

Images too large im going to post a link

Thanks in advance

Posts: 258
Joined: Tue Mar 03, 2009 6:47 am

Re: Triumph pre unit transmission

Unread post by graffian » Tue Jul 31, 2018 7:05 am

I haven't had a triumph box for a long time, I had a slickshift box behind my 45.

The cover is from the other type of pre unit box I used to see, I have no idea how many types there were.
Slick shift boxes have the has a ovalish/diamond cover, covering the clutch lever and the bit the
selector lifts. They also have a horizontal pointing clutch arm and they have the oil filler where it is
on your box, yours should have the cable stop there.

So it looks like you have some wrong bits. I have no idea which, check the number and see what the
shell is for?

Apart from the slick shift mechanism they were the same internaly as far as I remember.
I had a shell and stuck all the internals from an early 70's T120 in it, 4 speed, and when I had
my 45 I put T140 5spd box internals in it. But it was all quite a while ago.

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Joined: Sun May 17, 2009 8:04 pm
Location: Cheshire

Re: Triumph pre unit transmission

Unread post by Notsospeedy » Wed Oct 24, 2018 8:46 pm

Having just re-built my Triumph pre-unit box I can now recognise a few bits!

You seem to have a mix of parts there.
The Casing is from a swinging arm model because of the large mounting boss on top.
The Shell (middle bit) is a bit odd, it looks like a late model because the large filler is on top BUT there should be a bracket on top for the clutch cable to screw into, the inner cable then continues through to the lever in the outer cover.

What you have inside could be anything! Later boxes had needle roller bearings for the layshft and people commonly swap the plain bronze bushes BUT the later boxes had a slightly shorter layshaft to enable this.
Mainshafts and gears were virtually unchanged over quite a few years but the layshaft and 2nd changed significantly. You can't get early 2nd Layshaft gears and later one's don't fit early shafts!
Then there are selector forks plus camplate to investigate, later camplates DON'T fit early boxes - I found out they are significantly bigger and foul the mainshaft!

The Cover you have fits any of the shells.



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