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Propshaft for 3 Rail J-Type Overdrive Conversion -- Herald 1200


Anthony
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I'm planning on installing my 3 rail J-Type overdrive gearbox in my Herald 1200 shortly.

Could someone sell me what length propshaft I need?

I understand the D-Type boxes use a 46.5" -- 47" propshaft from a non-OD Vitesse, or from a 2000, but I thought I'd heard the J-Type boxes are slightly longer, and thus require a shorter propshaft.

Can anybody confirm?

Thanks.

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The J type is a fraction longer but not much, although it depends on the adapter block, too. I once changed a D type to a J type in a Vitesse and didn't have to change propshaft as the sliding spline had enough range. You may have to measure up to confirm.

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As above, if it is the late mkIV spitfire j type box it will use the same propshaft as the d type. It uses the rare thinner adaptor plate (I need one of those if you have a spare!) 

 

The idea of j type being longer comes from people fitting dolomite 1850 single rail geaboxes (or the internals in a 3 real case) as they use a thick adaptor plate. But the early dolomite 1850 OD box is still J type and is exactly the seam length as a GT6 etc box. (downside is it still has the small mainshaft tip, a much bigger issue than the OD type)

One further point to consider. The J type uses a different PCD on the flange to a herald, but is the same as Vitesse 2litre and indeed 2000. However, you may well have teh std herald diff, so will need a prop with different flanges each end (you have probably realised that though) Changing a flange or even just a UJ will probably put the prop out of balance a little. It has always done so when I have done it. Odd really, other cars it isn't an issue.

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Thanks Guys,

The gearbox is indeed out of a very late MKIV Spitfire.

 

Am I correct in saying that if I kept the standard diff I'd need to replace the rear flange on the replacement prop shaft (sourced from a Vitesse or 2000)

Or, if I replaced the 4.11 diff with a 3.89 unit I could use the replacement prop shaft as-is?

 

Out of interest, what diff ratio would everyone use on this car?

 

Engine will remain 1147cc, so it'll never have much torque, but should have somewhere north of 80hp when finished.

(I believe the first gear ratio changed from 3.75 to 3.5, all other forward ratios remain unchanged)

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I think I'd stick to a 4.11 with that engine. If you don't want to swap the propshaft flange, it's possible to swap the input flange on the diff. I believe it's simple on the earlier diff with the castellated nut - the later type with nyloc had a collapsible spacer which you'd need to be very careful not to crush any further, and you can't do the usual trick of marking position and counting turns if the flange is being changed.

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I think you might suffer on pulling away with the new gearbox and different ratio diff. Bear in mind that the 3.89 unit is whats used as standard in the 2L Vitesse...

To keep the same ratio it might be possible to fit the flange from a later differential to your existing one so that you then have the same on both gearbox and diff.  

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In all honesty, it appears you are spending a fair amount on the car. 

Don't skimp on the propshaft, one that is not perfect can make life a misery. So unless you have found a guaranteed perfect prop, I would be inclined to have one made, or get a used one fitted with new quality UJs (they are £20-40 a pop) and balanced. The correct flanges could be fitted at th esame time.

Plan B is to try a used prop, and sort the issue if there is one. 

As to ratios, a 4.11 is by far the best option, especially as you are having a hot cam etc (to achieve that 80bhp) so will be wanting to use the upper end of the rev range.

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  • 2 weeks later...

I've just found out that the 1200 gearbox uses a different "ball throwout sleeve" compared to the MKIV Spitfire gearbox that I'll be fitting -- It's the part that the release bearing mounts on to.

The Herald gearbox having a shorter "ball throwout sleeve" than the Spitfire gearbox.

Do I retain the Herald item, and fit that to the Spitfire gearbox, or do I use the Spitfire one?

(My car is a late 1200, so it probably has a diaphragm clutch)

 

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I think your car has the multi spring type clutch rather than the later diaphragm type used in the Spitfire gearbox youre going to fit. However with a bit of luck the bearing carriers you show are interchangeable and by using the old one you'll still be able to operate the existing clutch...

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According to the Workshop Manual the 1200 changed from a coil-spring clutch to a diaphragm clutch at Engine Number GA204020E.

My car is quite a bit later than that, so it should have a diaphragm clutch.

To my knowledge the bearing carriers can be swapped, and I believe they match the clutch rather than the gearbox. So, with that being said I believe I should use whatever bearing carrier comes out of my car......I just need that confirming before I start messing about.

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The manual I saw just said the change to diaphragm clutch was on the mk2 Spitfire while the 1200 and 12/50 had the coil type. Anyway, as you probably know, some Triumph information isnt 100% reliable so you wont be sure until you separate engine and gearbox. In fact the only guarantee the change is going to work is when its all assembled and you try it...

To have an alternative plan it would be interesting to know if anyone has swopped to the later type of clutch and how easy it is to do?

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Quoted from Anthony-

To my knowledge the bearing carriers can be swapped, and I believe they match the clutch rather than the gearbox.

I believe you are correct in that belief 😀

The gearbox is, in fact, identical between Heralds and roundtail Spitfires, as it the bellhousing. The MkIV Spitfire gearbox is different internally (extra synchro on 1st) but I believe the input shaft is the same, and the bell housing definitely is. So there's nothing different that matters where the gearbox is concerned. The only thing left, then, to explain that "ball throwout sleeve" difference, is the clutch.

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Looking at other threads Ive found the short carrier is for a coil clutch and although the operating arm is the same the slave cylinder maybe different. Certainly the coil clutch friction plate is thicker and the flywheel has different dowel holes for mounting the pressure plate.

Hopefully your car has a diaphragm clutch and then there should be no problem with the new gearbox operating the clutch as is... 

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This is interesting, I wasn't aware of the different bearing carrier lengths. I bought an aluminium bellhousing recently though, and noticed that its release bearing looks shorter than my existing one - and this would explain why. It's a Stanpart housing not repro, so will have come off an early Herald or Spitfire. 

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By the way, Anthony is that a wire wheel coffee table or something?! Looks like you've got a piece of glass cut to sit on top. Very nice. 

Quoted from Anthony-

I've just found out that the 1200 gearbox uses a different "ball throwout sleeve" compared to the MKIV Spitfire gearbox that I'll be fitting -- It's the part that the release bearing mounts on to.

The Herald gearbox having a shorter "ball throwout sleeve" than the Spitfire gearbox.

Do I retain the Herald item, and fit that to the Spitfire gearbox, or do I use the Spitfire one?

(My car is a late 1200, so it probably has a diaphragm clutch)

 

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Quoted from glang-

Looking at other threads Ive found the short carrier is for a coil clutch and although the operating arm is the same the slave cylinder maybe different......

Yes, according to Rimmers:

The Coil-spring clutch has a 0.75" slave cylinder, whereas;

The Diaphragm clutch has a 0.875" slave cylinder.

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  • 2 months later...
Posted (edited)

Update:

I've just tried to fit my aluminium bell housing to the gearbox and I can't get the bell housing past the input shaft.

The splines on the shaft seem to be a larger diameter than the hole in the scroll-seal opening.

Anybody got any ideas what's going on? --  Was expecting the bell housing to slide straight over the input shaft

Edited by Anthony
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The input shaft on the gearbox is 1" in diameter, with 10 splines.

It's difficult to accurately measure the diameter of the hole in the scroll-seal, but it seems to be approximately 0.938"

The release bearing on my aluminium bell housing is the later item (part number grb207) which corresponds to the diaphragm clutches.

 

Any ideas? -- Do I need to swap the scroll-seal to the later rubber seal set-up?

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4 hours ago, Anthony said:

I've just given the input shaft a closer inspection and I'm staring to think I might actually have a GT6 gearbox with a J-Type overdrive conversion

Have a measure of the input shaft length, tip to bearing/main case.

No idea where you are, but I have a late spit IV j type box here that I may be persuaded to part with, and I know a local who could swap your OD parts over to it.

Or if it is easier, see what you have and purchase the correct OD conversion complete. A d type OD will be plenty strong enough if you cant find a j type.

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I am in Brighton. It is a 3 rail late mkIV Sputfire box. No overdrive parts though, so would need your adaptor plate, od etc. I bought it as a recon box from Speedy Spares (mainly rootes now)

I have a local gearbox man who is good and very reasonable. He has built many triumph boxes for club members...

 

 

 

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