www.jec.org.uk

Part of the refurbishment of my SIII XJ12 I would like to fit a manual box. I have been offered conversions from different sources; the 5 speed Cosworth/transit box, the XJS 3.6 box, a 5 speed Supra box or I could fit a 4 speed from the E type V12. Does anyone have any thought's or views on the above... I obviously would like to take the safest but also the cheapest route which seems the E type box, I'd actually be happy with 4 manual ratios and would not have to change the diff as you would need to with some of the conversions..

By the time you've collected all the necessary parts, I'm not sure any of the alternative boxes would satisfy your criterion of 'cheap'! The V12 produces a lot of torque so whichever box you choose needs to come from a high torque application rather than a vehicle simply producing similar power otherwise you could wear out bearings and shafts quicker than planned. Going to all the trouble of making the conversion, it would be a shame not to aim for five speeds despite the relative ease of fitting a V12 E-Type four speed box. Why not consider a Jaguar four speed plus overdrive unit with a V12 bell housing? Plenty of people have made these work behind a V12. Mike.

Thanks once again Mike for your feedback, when I say cheap I mean as reasonable as possible, I really don't want to spend loads 6K + on a conversion, but if I can get it done for half of that or near enough I'd be happy and able to part with that amount... I've been quoted 6k for a used Gatrag conversion, about the same for a new T5 conversion, OR have seen a supra conversion for half that amount which retains the standard diff..... all are able to accommodate the modest (by todays standards) torque figures. I suppose I was hoping for someone on here to say, hey, I have a reasonably priced kit for you. I really like the idea of a manual V12, still have strong memories of smoking a E type manual V12 some years back...

Have you spoken to simply performance?
They have done a lot of conversion work.
https://simplyperformance.com/v12-5-speed-conversion/
https://simplyperformance.com/wp-conten ... t-2018.pdf

Have you made a decision on which gearbox you will use for the conversions?
I am just looking at the same conversion and simply performance kit looks
good.
Will be contacting them for more information.
Would be interested to know if you decide on a different set up.

I have not yet made any decision here, cash flow in these current times has been an issue.... but yes the more I delve in to this the Simply kit looks the most promising one, but it does mean a change of diff as well and that just adds to the expense... will keep you guys posted