Fitting a gearbox With Overdrive (and an update on our Jupiter)

[harrynaerger]

Good evening all,

Hopefully you can see the images that show our spare gearbox with attached overdrive? Could anyone (Keith perhaps??) let us know how easy it would be to switch from our original gearbox to the new one? Does the propshaft have to be modified in anyway or does it just simply slot straight in having taken the original gearbox out? Our original gearbox is in need of an overhaul so we thought we would try the spare and see what its like.
We thought the overdrive might be useful for the Mulsanne Straight if we do get accepted for Classic Le mans!
You may also be interested to know that we put the car on a rolling road at Aldon Autos in Stourbridge on the advice of Julian Crossley and after the excellent technician had played around for a few hours he managed to get us 104bhp at the flywheel with max power at 5640 rpm which we were delighted with. I think we might be 20 hp better off than we were! We think that might even be slightly better than Julian but don't tell him!!
Any advice on the gearbox fitting would be very much welcomed.
Yours Harry N

[Forumadmin]

Good news on the power output. Do you know what was done to tune it?
Was that with the standard or modified exhaust?

Regarding overdrive. Every overdrive mod is individual, so you need to check if any mods have been done to the clutch housing, gearbox supporting bracket or chassis cross member, or the prop shaft and its yoke/layrub.
You should be able to put a standard box in with a standard prop if the chassis mounting has not been altered.

You will definitely need a very low ratio to do the Mulsanne any justice. 16 inch wheels , low ratio diff, and overdrive as 120 mph is possible with enough power. You will run out of revs otherwise. As you know your peak power revs just work it out.

[harrynaerger]

First thing he did was take the distributor to bits and rebuilt it.
Then he drilled out the jets in the carbs.
I think one of the HT leads was a bit iffy so he replaced that too.
It was with the modified exhaust.

After some further thought we think we'll try and get hold of another gearbox and get the guy that Julian C used to rebuild it with modern parts.
We can then stipulate which ratios we want.
So if you know anyone with an old gearbox that they no longer need we would be happy to purchase!
Presumably Javelin & Jowett gearboxes are interchangable??

[Keith Clements]

I have a gearbox or two what parts do you need if you are putting new parts in it?
I have many casings and mainshafts.

[harrynaerger]

Thats good to know!
I haven't heard back from Julian yet as to where he took his gearbox but I will chase him over the weekend and find out just what we need.
Many thanks Keith