Gearbox Interchangeability

[yellowbelly]

I have a 1972 Marina 1.8TC based roadster. The gearbox is useable, but third gear doesn't always select smoothly.

A friend has a NOS gearbox that he bought years ago for a 1970s Triumph Dolomite Sprint, but never got around to fitting.

He thinks that BL used that box across their range, and is confident that it would be a straight swap.

It sounds too good to be true, but is he right?

[martinclan56]

As I recall the internals are the same. But I have a feeling that the mainshaft nose may be different. The bit that locates in the crankshaft.
The guys on the Morris Marina Owners club will be sure to tell you.Their website is fastmarinamagazine. I think you can post a question without a login. If not you can probably search as I think the question has been asked before.

[Ye Ol Ripper]

With regards to the selection problem, do you currently have a lot of play on the gearstick? I ask as I can advise of the replacement part to order to tighten things up. I replaced mine last year. Another problem is a failing clutch slave cylinder. Is there any evidence of fluid leaking from behind the dust cover. Have you checked the oil level as they leak & it might need topping up?

[A_Hogg]

Regards the use of a Dolomite box - take a look at the Tech Tips articles part one for the Roadster . It's all there and is easier for me not having to write it all down!

[yellowbelly]

When I got the car, there was some evidence that the slave cylinder was had been weeping. It appeared to be the only part of the system that hadn't been replaced, so I bought a new one, butas the fluid level has never dropped, I didn't get around to fitting it. I've now done so, and I'll report back when it has been bled through.

[TVRFan]

This might be wrong, but -

As far as I know Marinas used 'small' Triumph gearboxes and diffs, from the Spitfire/Herald/Vitesse and onwards to small Triumph saloons (1300,1500,Dolomite). Dolomite Sprint used the 'big' gerabox (TR4,5,6, 2000,2500 saloon,Stag) and diff. So some parts would likely be interchangeable from Spitfire range. It may not fit directly to your 'B' series depending on whether the bellhousing is same depth (i.e. from engine block) or may need correct input shaft. If you take a good look at a Stag or Dolo Sprint, you will see they actually have a factory made adaptor plate, as the 'big' box doesn't have separate bellhousing, so Triumph made a longer input shaft and a plate .... Both gearboxes came with overdrive options.