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gearbox and overdrive to be fitted into.... what?


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So, I came across a cheap gearbox plus J-type out of a Saloon and bought it. Big question now is in what car should I put it! 

TR4? I have owned this car for 25+ years. Has the non-overdrive gearbox. Love this car, good on the motorways up to around 80 mph which is about the top speed when driving open (which is most of the time). When going faster too much wind (noise and the wind itself). I never really thought an overdrive would benefit much. On the motorway the rpms would go down what, 700 rpms? Maybe the faster shifting from 3 to 3OD instead of the change from 3 to 4 would come in handy on curvy roads.

GT6 Mk2. This is a car I bought a couple of years ago to be restored which will be done in 2/3 years time (I hope). Now has the standard 4 speed. I can imagine it will be more of a benefit compared to the TR4.

Stag. Same situation as the GT6 however this car will be road-ready much earlier. Now has the standard 4 speed. As more of a Grand Tourer having an overdrive will be a benefit on the motorways I think.  

I have not looked up what is needed to fit the GB+OD to either car.

It will bolt on to the TR4, which would need a Saloon clutch and a adapter mounting at the rear. And an angle drive for the speedo cable. Anything else?

I would guess the GT6 and the Saloon both using the 6 cylinder it would fit straight onto the GT6 engine but could be wrong. Do they have the same back plate? Did the GT6 have another gearbox compared to the Saloon? Any physical differences? Is there room in the frame to fit the Saloon GB+OD? 

Stag - I seem to have read that this will go but not sure what would be needed. Straight fit? Is the Stag GB same as the Saloon GB?


But regardless of how difficult it is to install, main question is what car would be best having the overdrive? What would you do and why?

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Stag uses a longer, unique input shaft. But there are people around who can do q mix and match from your  2 gearboxes. That is the best bet.

Tr4, simple fit and the benefit of a nicer clutch action after.

GT6 not so easy.... It uses a smaller box, essentially a herald box with different internals and input shaft.

One more thing, the saloon box had a low first gear, doesn't sound much, but very noticeable. As are the benefits of overdrive ...

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19 hours ago, badhuis said:

But regardless of how difficult it is to install, main question is what car would be best having the overdrive? What would you do and why?

I like overdrive; it's like having a modern car with four gears when others have five or even six.

I used to drive round town in third, just flicking overdrive in or out as the need arose without having to go near the gear lever, and of course at higher cruising speeds it drops the revs to a more comfortable level.

It all depends on the car, and your intended usage, I felt that my GT6 needed it but none of my Heralds have it.

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