Alternate 5 speed gearbox

[Edmund Nankivell]

I have long thought we need a total redesign of the gearbox, entirely new innards - a 100% redesign internally. All Jup and Jav owners around the world would contribute cash. The alternative is to find a gearbox of a classic car such as TR2 or such like, a classic car that will live for ever, and adapt its gearbox to fit. I am afraid that otherwise it is the gearbox that will ultimately kill the car.

[Andrew Henshall]

Dear Edmund,

Can you summarise the gearbox issues that resulted in you coming to this conclusion?

The issues that I am aware of and the solutions we use down here are:

Failure of layshaft roller bearings - replace with improved version supplied by JCCA
Failure of selector bars - replace
Wear in hole in case where the gear operating shaft enters the gearbox - machine out & fit a bush
Wear on gear operating shaft - replace or build up & regrind
Broken operating shaft spring - replace with spares supplied by JCCA
Wear in selector bar notches - replace or build up with Stellite weld and re-profile
Wear in selector lever pad - shim as necessary
Worn selector plungers - replace or build up with Stellite weld and re-profile
Noisy in indirect gears - use ear plugs
Weak synchros caused by worn cones - re-lap cones & cups
Oil leaks - machine grooves in gearbox housing where it mates to the clutch housing & fit O-ring seals. Plug the layshaft clearance hole in the clutch housing with a cup type core plug 7/8" OD & 3/4" max ID & seal OD with Loctite 290.

Now the list above is extensive, but surely any gearbox out of a TR2 will need many of the repairs above anyway?

If your concern is a lack of spare gearboxes globally, then I think you will be surprised at just how many are squirreled away in sheds belonging to club members. I have quite a pile myself!

Cheers,

Andrew

[Edmund Nankivell]

Both my Jupiters have well-repaired gearboxes. But one jumps out of 3rd on the overrun from 40 to 30mph, the other one now, a new fault, INSTANTLY jumps out of reverse, but I can hold it in reverse with the gear lever when I need to reverse the car
Do I want to get the gearbox out every time one or more of these faults occur? No I don't. I have overdrive ob one car, and a 4.1:1 cwp in the oter. 5-speed would be nice!

[Forumadmin]

The 'obvious ' issue with the gearbox is that all of the gears themselves wear and there is no alternative to making new gears. I do not think this is likely to happen. Whilst many faults can be rectified as stated by Andrew the gears do become sloppy. I have welded up broken first gear teeth on the layshaft, and you might be able to recondition clusters using some metal spraying and recutting technique. hat it really needs is someone with a spare CNC copying machine to take on the task. Some companies I have talked to at shows would be quite happy to take on the task, and some might happily pay the £1000 it would cost.

The overdrive is the best way to provide you with the fifth gear as it retains the Jowett gearbox. The alternative is to depart from originality and the Jowett engineering that makes our cars unique. Many components are now being replaced by modern equivalents and it will be a shame to not have an 'original ' car to view at future meetings. Even LED bulbs, alternators, different carbs, paint, upholstery, will all detract from the aesthetic value (and resale value) of any Classic Car.

This point on originality was made very clearly at the Anson Motor museum to me.

However, if such components keep a Jowett off the road then alternatives should be sort but with the proviso that the car can easily be returned to its previous state.

[Jack]

Both my Jupiters have well-repaired gearboxes. But one jumps out of 3rd on the overrun from 40 to 30mph, the other one now, a new fault, INSTANTLY jumps out of reverse, but I can hold it in reverse with the gear lever when I need to reverse the car
Do I want to get the gearbox out every time one or more of these faults occur? No I don't. I have overdrive ob one car, and a 4.1:1 cwp in the oter. 5-speed would be nice!

I agree that it would be nice to have, especially if it can be easily modified by the home mechanic to fit a 5th gear - the question is how to do this without losing the column change (a very visible and in my opinion important part of the cars) and assuming we keep the column change how to make the necessary changes to the mechanism without complete reengineering.

For pure useability purposes changing to an alternative 5 speed box and floor change wouldn't be the end of the world - assuming the gearstick comes through the wooden floorboard this is easily removed if an owner wants to return to complete originality.

In an ideal world we would find a fairly modern (1970s onward and common) 5 speed box or four speed with overdrive that can stay in the Jowett housing and retain the column shift, but will require quite a lot of expertise and some proper headscratching I suspect.

Isn't the Sierra box already in use for a modern 5 speed replacement? From memory the MK2 had this fitted to a Jupiter engine? Presumably this required floor change to go with it, but should be achievable by a home mechanic at reasonably small cost. Finding a replacement that fits the Jowett housing is probably more complex, but there must be gearbox specialists who would spend a couple of hours looking at a range of alternatives to see if there was a fairly straight swap?

Jack.

[Chris Spencer]

The Ford type 9 gearbox change is already documented within this thread - to re-engineer a Jowett 4 speed gearbox to a 5 speed would cost several £k - it would be easier to start again with a all new housing - the column change need not be an issue and could be retained however - with some technical application the new gearbox - and even the type 9 Ford box could be operated by servo motors with a pick up off the column change - it just needs someone with more spare time than enough to work out what and how to set it up / install it - once done it could be offered as a kit - many popular classics are now being made more drivable by 5 speed gearbox conversions / upgraded brakes / steering / engines / performance products etc - its not everyone's idea of classic or of how to use it - but if it keeps it out there - on the road and the owner happy - who am I to complain - its more the vehicles that get the bodywork butchered for sake of atheistic looks that I hate

[msuemason]

Call me old fashioned, but I can't find where to access a new post so.... This is nothing to do with 5 speed gear box but hope it can be located in the appropriate section. So......
On a recent Jowett jolly to France in our Jupiter, we were parked amongst the Glitterati going to LeMans. A young man jumped out of a Porsche exclaiming: that's a Jowett Jupiter! Amazing in one so young! To cut long stories short, he told me he was married to the Granddaughter of Reg Korner, designer of the Jupiter.
I have stayed in touch and he has passed on my accounts of Jowett in activities to Roger Korner, son of Reg, who now lives in France.
The most recent email I received from Tiger ( yes that's his name) offers a cuppa to anyone going to Goodwood who might be passing - I assume in a Jupiter.
Let me know if any Jupiters will be on the A286 south of A3 on way to Goodwood where a cuppa. Is on offer. Three small great grandsons. Would also be delighted to see their heritage.
Please post in relevant place.

Sue

[p.p.]

Call me old fashioned, but I can't find where to access a new post so.... This is nothing to do with 5 speed gear box but hope it can be located in the appropriate section. So......
On a recent Jowett jolly to France in our Jupiter, we were parked amongst the Glitterati going to LeMans. A young man jumped out of a Porsche exclaiming: that's a Jowett Jupiter! Amazing in one so young! To cut long stories short, he told me he was married to the Granddaughter of Reg Korner, designer of the Jupiter.
I have stayed in touch and he has passed on my accounts of Jowett in activities to Roger Korner, son of Reg, who now lives in France.
The most recent email I received from Tiger ( yes that's his name) offers a cuppa to anyone going to Goodwood who might be passing - I assume in a Jupiter.
Let me know if any Jupiters will be on the A286 south of A3 on way to Goodwood where a cuppa. Is on offer. Three small great grandsons. Would also be delighted to see their heritage.
Please post in relevant place.

Sue

i meet them last year in goodwood...there had a taxi drive with a jupiter and back with the javelin.....fun and a big smile...all two ways!!!

[Alf Heseltine]

There is a report of Lawrie McKee fitting a 5 speed Toyota gearbox to a Javelin. Reported in the recent
Issue of New Zealand Flat Four mag,( page 23) For those interested this might be worth checking on.

Alf.

[ganey2]

We have considered the 5 speed box question for the racing Jupiter but because of the FIA HTP papers it is really out of the question. The Jowett box has to stay if you are going to pass scruitineering at the big events. There is an Alfa box from the 70s that doesn't look too different but it would be big risk to take. We have done only modest re engineering of the Jowett box and so far it has been holding up...even using first for fairly aggressive starts. Maybe the light weight helps though.