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Courier gearbox article


gt6chris
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May be a typo but Derek's article has got its single and 3 rail boxes confused. He is clearly rebuilding a 3 rail box but the article suggests that it is a single rail box. The single rail has a single selector rail whereas the 3 rail has (you guessed it) 3 selector rails. As Derek says the internals of all the small Triumph boxes are quite similar (not necessarily the same) other than the early boxes with no syncro on first gear.

 

Chris

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the internals of all the small Triumph boxes are quite similar (not necessarily the same) other than the early boxes with no syncro on first gear.

 

Chris

 

My car has no syncro on 1st, and it is a 1969 Herald, so not an early box.

 

Elsewhere on this forum I am sure someone said that no Heralds had syncro on 1st. 

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That's correct Eddie. All the 4 cylinder 3 rail boxes were 3 synchro. 4 synchro being introduced with the single rail.

I was thinking of the early 6 cylinder boxes. The Vitesse 1600 was a 3 synchro box whereas I believe all 2 litre boxes are the 4 synchro variety.

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That's correct Eddie. All the 4 cylinder 3 rail boxes were 3 synchro. 4 synchro being introduced with the single rail.

I was thinking of the early 6 cylinder boxes. The Vitesse 1600 was a 3 synchro box whereas I believe all 2 litre boxes are the 4 synchro variety.

 

Chris,

 

The MKIV Spitfire has a 3 rail 4 synchro box, so it is conceivable that the very last Heralds were also fitted with a 4 synchro box.

 

In the Spitfire world, the single rail box was introduced with the UK/European Spitfire 1500.

In the USA, the MKIV Spitfire got a 1500 engine in 1972/3 - a good 18 months earlier than UK/Europe, and the early US 1500's had 3 rail boxes, and got the single rail box at the same time as the UK/European 1500 was introduced.

 

I'm not too familiar with the Dolomite range, so I'll leave it for someone else to say when the 3 rail 4 synchro Dolomite box was introduced.

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Many parts between 3 rail vs 1 rail do seem similar, when collecting a slave box to convert my 3 sync 3 rail to 4sync 3 rail the slave box had been refitted with a right mishmash of parts by some ill informed owner who im guessing gave up, this including the 1/2 hub being single rail and a rattling good fit on the 3 rail mainshaft followed by extra teeth on reverse which

would not engage with anything so most of it was a waste , the main shaft spigot had beed carefully replaced with boring the shaft aand adding a slug ground to size, just it was left loose and had wrecked the stem gear bore,

 

so yes seems you can mix and make the parts fit , but certainly wont operate as a gear box.

 

the joys of bargain unknowns

 

There was also gear tooth profile changes to later boxes for quiter running.

 

you cant mix these unles you loke a whine

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Good Morning.

 

Early Triumph Dolomite 1850 used the same three rail box and clutch including the release arm as the GT6 and 2L Vitesse, you need to change the bell housing. My Vitesse has a three rail gearbox, reverse up by first with a J type overdrive, but has the fine input shaft from a single rail gearbox. This gearbox came with loads of other bits bought at a show some years ago. The box works very well the only trouble was the overdrive slipped on moving off, had it refurbished and the pressure correctly set for a 2L Vitesse, now the overdrive engages very smoothly.

 

Regards

 

Paul

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I use a similar set up on my GT6 but with a D type overdrive. It has the Dolomite 20 (?) spline input shaft and matching main shaft which has the larger tip. this is built up with a GT6 gear set. My original box was made up of a variety of dubious parts and a damaged lay gear cluster so I gave it all to Mike Papworth to sort out. Out of all the boxes I have worked on over the years the biggest killer was the main shaft tip wearing out.

 

Chris

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I'm not too familiar with the Dolomite range, so I'll leave it for someone else to say when the 3 rail 4 synchro Dolomite box was introduced.

 

I think I can remember them all.....

 

As mentioned early 1850 has a GT6 style 3-rail but with a J-type. All 4-synchro. Late 1850 has a single rail

1300 dolomite will be single rail non-OD

1500TC will be 3-rail 4-synchro non-OD

Toledo will be 3-rail 4-synchro for early ones and single rail for the very last ones. Both non-OD

1500HL will be either single rail with J-type or non-OD

1500SE is single rail non-OD

 

Sprint is a TR box.

 

All Dolomite is 4-synchro.

 

Cheers

 

Colin

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