Gearbox

[David Kemp]

If a Jowett Javelin gearbox needed rebuilding, would money be better spent adapting a modern five or four speed box? Particularly if the car is going to be driven, I ask as the box does appear to be Jowetts weak point. Or are all it's faults now got permanent cures? ei jumping out of gear, stripping 1st gear........ What are the common boxes people have used?

[Jack]

Rumours abound that the Sierra 5 speed box is pretty much a straight fit with an adaptor plate to the Javelin engine.

Not sure who did it, whose car or engine it was done to, but I am sure that a friendly breaker would sell you a Sierra box for very little (sub-£50) to try it on a sale or return basis.

Of course this would mean a floor change unless you did a lot of work to make the column shift somehow fit with it, or I suppose an auto box would be fairly easy to control using remote shifter - a lot of modern auto boxes aren't actually connected to the lever next to the driver!

Jack.

[Robin Fairservice]

I have seen a Jupiter in Australia with a Ford Sierra box. I think that the owner's name was Brian, possibly, Cooper. Keith was there, so may be he would remember the name.

[george garside]

a couple of thoughts!

- In many years driving Javelins fairly hard as everyday cars I never had any gearbox trouble so for the limited mileage most (non competition) Javs now do the ordinary box, properly checked over and overhauled as required, should be absolutely fine.

- Fitting any 'modern' box will result in a much higher first gear which could well be a disadvantage in starting on steep aclivities or towing a trailer or whatever.
In my view it would also be a bit too much of a departure from origiality

- there have been and presumably still are good overdirive conversions dating back many years slinging the overdrive in place of midship bearing. this would not interfere with the first gear ratio which was chosen because it was needed, would give a higher top gear , be easily reversible, wouldn't result in gear leavers poking out of the floor and could be deemed to be a ''period'' conversion as Borg Warner overdrives were widely used by other makes in the 50's and indeed one was fitted by the factory to one of the prototype R4 Jups.

To be honest, in my view, if you want a ford sierra gearbox you might just as well retain the rest of the ford sierra!

george :

[Forumadmin]

I do agree with George and the answer is to overhaul the Jowett or Meadows box properly. Most boxes have wear in various places and most of this can be overcome with some refurbishment, but it does take time and experience and of course money. I must admit I have got through more gearboxes than engines in my many years of driving Jowetts. But many of those were not thoroughly refurbished, just the obvious bits were 'fixed'. You also have to realise that I hammered the boxes on many long gruelling journeys.

There may be some parts of the box such as the gear clusters where it is not only difficult to detect the wear but very costly to overcome the wear. The real issue is cost if you are paying someone to rebuild the box. Cost will go up exponentially as you try to fulfil your desire for reliability. A simple rebuild with parts available from JCS such as washers and bearings may take 20 hours. The degree of checking would only be superficial. If you then wanted wear to be eliminated on the gear clusters and synchro rings then expect many more hours and much more specialist refurbishment cost.

I did have gears checked, blued and honed on one box; but that requires expertise that is now difficult to find.

The question is 'are you employing fitters or engineers to do the job'?

The other issue with gearboxes is the drivers. Many are not sympathetic with the unusual gear change and older car driving technique. So just one impatient move can destroy a box. Probably the majority of boxes in use are not perfectly set up so wear and problems accelerate in frequency. The propensity for boxes to leak oil also means that at sometime in their life they were without oil, thus accelerating wear. Add to that poor original manufacture and you will need time and effort to rebuild a box well.

[Jack]

Another idea - what about if you could retain the column shift and the reliability of a more modern box?

Nobody ever gets to see the gearbox - it is hidden underneath and behind the engine, the only visible part really are the linkages from the column shift if you really check under the bonnet of a Javelin.

Ford Type F gearbox - if a Sierra box fits, it can't be a huge modification to get this to fit too - it has the same 1" 23 spline input shaft and very similar shape.



Those levers on the side should make a column change an achievable task.

All this said, there is no shortage of post war gearboxes. Everyone seems to have half a dozen of the things, and every pile of spares collected seems to have another 3 or 4 included, many of which are perfectly useable and reliable with minimal work. I guess because people took the engine and gearbox out before scrapping cars, but we should consider planning for the future.

There may come a time when replacing a gearbox with something different is the only option - either because of cost, lack of awareness of how to rebuild a reliable box, or just to fit a day to day box which is one of millions manufactured to avoid wear and tear on an original item.

I certainly think it is worth our time finding out what fits, and what modifications are required in order to make it work. Perhaps a job for the winter. If looking at Sierra boxes, worth considering a 5 speed Type 9 box from the Capri and a couple fo others instead of a 4 speed Type E - the 5th gear gives a better ratio for motorway use, and no shortage of either available second hand.

Jack.

[george garside]

As it is now 60 years since the Jav ceased production and we still have a surfeit of gearboxes and taking into consideration that a great many of the surviving cars) ( like most of their contempories of the 1940's may well take 10 years to cover the mileage that many once covered in a single year it is highly unlikely that we will need to source 'foreign' boxes.

A higher 'crusing' ration can be had byh using an overdrive which will also provide a useful ''high third'' on the Meadows boxes


Whilst in engineering terms many things can be made to fit many things the Ford box has both selector leaver moving in a for and aft plain a
ginst the Jowetts one for and aft and one across the beam so to speak so would the added complication realy be worth the effort for a maybe a few hundred aand unlikely more than a few thousand miles a year.

I am sticking to my view that retaining the Jowett/Meadows box is the way to go and that so doing will meet all future needs!

george

[David Kemp]

Would it be better to find a few Meadows box's & rebuild them , than rebuild the Jowett box's? Or are they just the same, in design & durability? Any one fitted an overdrive?

[Forumadmin]

Meadows boxes are better but of course they too will suffer from wear and abuse. Since they would also be older than Jowett boxes and more desirable they may also have done many more miles.

Many people have fitted overdrives. Just search JowettTalk to answer your question. e.g. http://jowett.net/forum/viewtopic.php?f ... ive#p12914

[george garside]

It is possible to use a secondhand overdrive unit eg the one that was on a lot of rootes smaller models , sunbeam rapier, Hillman hunter etc, It was also on somme Vauxhauls mongst others. The larger one used on Mk2 Jags is probably too big for the jav. I don't know whether anybody is selling adaptor plates for the front incorporating with oil seal and bearing but an engineer friend made one for me without any problems . It is also necessary to moify a chunk of the doner gearboxes mainshaft to take a prop shaft coupling.

george

[Chris Spencer]

The Ford type 9 gearbox will fit (Serria / Scorpio) - it requires a 25 mm spacing / mounting plate off the bell housing - the original Jowett clutch plate can be used but the centre requires swapping over to match the gearbox main shaft splines - the prop shaft would also require modification to shorten it - whilst you probably also have to look at lowering the engine within the chassis by 25 - 40 mm in the Jupiter - in order to clear the floor - Javelins should be ok without engine mounting modification - downside is that you end up with a floor change gearbox - but the type 9 box is very close in ratio to the Jowett box and you get the all important 5th gear - I appreciate not something for the purists - but for someone like me that has virtually enough bits (from several cars) to build a Jupiter Special - hence the research - Alan Fishburn has already tried & tested this conversion.

[David Kemp]

Any one tried an 80's Volvo? as many have overdrive. Anyone tried putting Amazon hubs on Jowett back axle, as they have the same 3ha diff?

[Jack]

Interesting discussion this afternoon at the Bletchley Park meeting. Richard Gane has started racing his Jupiter, and has got a floor change gear mechanism using a Jupiter gearbox.

No idea how, or even why, but it has now been done. Hopefully we can get him to share how this operates. Not sure if this has been done before.

Jack.

[george garside]

possibly sometime in the 70's somebody in New Zealand fitted a jav/jup box to a CC Bradford the conversion incorporating what I remember as a very straight forward conversion to floor change. It was fully written up in ''flat four'' and , not sure, but may have been reprinted in the Jowetteer. The conversion would haave wrked just as well in a Jupiter. There is also the R4 ''conversion'' of the same box to floor change with long horizontal tube to the remote gear leaver. I don't know whether the box was turned round to bring the selectors to the top or whether it was a different casting. The jav/jup box was based very closely on the 1940 8/10 box which of course had a floor change but not the long stern tube , maybe the R4 boxes used 1940 casings with the addition of a stern tube. Jowetts certainly used one experimentally on a twin carb CC Bradford so probably had quite a few in stock as a result of the curtailed 1940 production.

george

[Forumadmin]

It is a long time since I looked at the R4 box at Rushden when it was being rebuilt. From memory it was a completely different casting and clutch housing.