Triumphrat

moharrow

I am currently rebulding my 1978 t140 and was given by a friend of mine a set of T140 cases with the transmission intact (he bought the motor for the head and other top end parts) I believe the motor he gave me is a 1977 will the high speed gear fit?

pookybear

Moharrow,

What? I read this twice and still I am missing the point. I am
sure it is just the terms being used and it will all become clear
to one of us.

The stock transmission for a 1977 is a five speed gear box.
But please note that the earlier four speed gear boxes have the
same top gear ratio. Both have a top of one to one. The
only way to change gearing is to change sprockets on the secondary
drive or some of the belt drive conversions for the primary can
also change the ratio some.

So unless you have something made for racing that I do not know
about, which cover a lot really, I do not know about a high speed
gear.

Pookybear

thirdbike

Welcome to the site. You do have to try and be a bit more clearer when asking these type of questions to get the answer you need.
i think I know what you are asking.
If your question is, will the top gear from a 1977 fit in a 1978 Triumph 750 gearbox? In other words, is it (they) the same part? The answer is maybe. The layshaft top gear is the same part number but the mainshaft top gear assembly has a different part number. That, however is not to say that they cannot be swapped.
Someone else may know more about that