Hi guys.
I need your experienced input on my XJS project I am starting. I have a donor Right Hand Drive 80 XJS. It has no engine or drive train(no differential either)
I have found a replacement V12 engine and now looking to put a 5 Speed manual transmission. Didn't some factory XJS V12's come with 5 speed manual? Were they getrag's? 260 or 265?
Can I use a getrag wih my V12? Will it support the V12 support? I see that there are some manual transmission conversion kits out there. Is there a better option for selecting a 5 speed transmission?
Will any XJS differential be compatible? or do some XJS years have different gear ratio? Will that be a problem?
Your input is most appreciated since I am new to the XJS V12.

 

I need your experienced input on my XJS project I am starting. I have a donor Right Hand Drive 80 XJS. It has no engine or drive train(no differential either)
I have found a replacement V12 engine There are a number of variants, which one do you have, and do you have all the electronics it needs?


and now looking to put a 5 Speed manual transmission. Didn't some factory XJS V12's come with 5 speed manual? No, only the inline 6s, and their OEM gearbox's durability is a bit iffy on the V12

Will any XJS differential be compatible? or do some XJS years have different gear ratio? Will that be a problem? All rear axle assemblies will fit the chassis. The diff ratio you need (various from the factory) will depend upon your gearbox choice.

 

Greg
Thanks for the reply.
I purchased a 92 XJS V12 engine with the ECU. I also purchased the 92 differential as well. Which 5 speed manual transmission would you suggest? Will the getrag 265 not work?

 

Different ignition systems between those years (92 &80) and may well be less trouble to convert motor to lucas ignition rather than try to adapt the existing to marelli with harnesses, amplifiers and other bits and pieces likely to be a headache.

 

Long and expensive way to get get there. You are far better off starting with a running and driving XJS. They're cheap enough. Then do a 6 speed conversion. Not that the extra gear is really necessary but itsa cleaner and easier conversion. The 5 speed 260 conversion is sloppy...requires adapters on top of adapters and other parts not meant for a v12. Also any getrag you find now will be very old and who knows how well it works. The 2 down sides to a 6 speed conversion are that it's necessary to trim about 2 inches of metal off the shifter opening on the trans tunnel and they work nest with 3:31 or 3:54 gears.

That said, an V12 XJS with 3:54 gears and a new T56 6 speeds is an absolute joy to drive.

 

Sorry to partially hijack this but has anyone here got experience with 4-6spd automatics in these cars? I'll be doing trans & performance stuff soon on my car once the 52 separate oil leaks are resolved. I can't do manual in the city, and I'm dead set on paddle shifters at any cost.

 

Hi icsamerica
Thanks for the input. 6 speed you say? Which transmission conversion kit or shop would you recommend for the 6 speed manual ? Would this be the easiest way to do a conversion? V12 Fuel injection or V12 Carbureted?

So far i have found the following sites that offer the Jag V12 transmission conversions. Are there others you recommend?
www.vintagejag.com
http://simplyperformance.com/

Thanks

 

Try conversion components in NZ
Click the ‘select a vehicle’ button at the top to get the Jaguar options.
He offers 3 different gearboxes - Supra, Tremec, and R154

Conversion Components

Prices in NZ Monopoly money !

 

Al NZ
Thanks for the link. Out of the 3 gearboxes..which is the best? I also saw a Borg Wagner gearbox on the vintagejag site. Your thoughts?

 

I'm only familiar with the Tremec TKO 600 5 speed, it will take anything a street driven XJ-S will give. As with the EFI I needed my computer sent to UK's Roger Bywater to be reworked. Can't speak for carbs.
As said above the 3.54 is the way to go, considering the trans gear ratio's and remembering (@ least IMO) the stock IRS & 10 bolt diff are now the weak link in the driver line chain. Drag racing, burning outs & hole shots are a no no

 

44 lawrence
Thanks for the input. Much appreciated.

 

They are some way from you! But look at simplyperformance.com here in the UK. They can supply all the parts to fit a Getrag 265/290 straight onto the V12 XJS. Incredibly helpful and do international shipping. Contact Jon or Ben Thompson and mention me, Andy Cloud.
Thanks

 

IMHO you want a cast bellhousing rather than a stamped bell housing.

If you don’t mind the tunnel mods required & really need the double overdrive, then the Tremec T-56 is the way to go.

Otherwise, the TKO-600 is the best choice (0.82 5th if you’re not bothered about relaxed, low revs, high speed cruising & 0.64 5th if you are).

Why anyone in 2018 would fit a Getrag 265 or 290 is beyond me: the boxes will be between 20 & 35 years old - they must have some wear & tear - that’s before you stick the poor thing behind a V12 engine whose torque they weren’t designed for in the 1st place. AFAIK parts are either expensive or NLA - AND they need specialist repair/tools.

Fidanza aluminium flywheel is the way to go as is a ‘proper’ pedal box (not an add on pedal) from the appropriate XJS (i.e. ABS or non-ABS) & you want a 3.54 rear end, not a 2.88

Spend time sourcing the correct components & you will end up with a ‘nice to drive & reliable conversion’ - rather than a notchy, unreliable PITA.

Rgds.

A.

 

The 92 engine should come with 2 ECU's one is the fuel ECU and one is ignition ECU, you will need both of these for the engine to run, or you will need to convert the Marelli to mechanical ignition timing. Personally I like the Marelli it is a much better system that the mechanical if maintained.

Dellow in Australia have cast bellhousings for a number of transmissions to the Jaguar V12.

To fit a T56 you will need to widen the transmission tunnel, a 5 speed from a V8 Ford might be a better option or a TKO if funds are available.

 

Warren, so your saying the 92 MY has two computers that have to be changed as apposed to the 91 (that mine is & also Marelli) and I didn't do anything to the Ing computer . As I mentioned above that I had to have my EFI computer reworked because of the "fuel overrun". Without getting it reworked the engine would stall between shifts, other than that I had no other computer related issues.

 

I saw the 92 engine and 80 donor with no mention of a 91 so made an assumption you were rebuilding the 80.

If your car is Marelli then the 92 engine should work, just be aware there are at least 6 different Marelli ECU part numbers.

 

Bigpigpants, Isn't this backwards (or maybe my thinking is...) It would seem to me that the 0.64 5th gear would result in lower rev high-speed cruising as compared to the 0.82. It would seem to me that the deeper we go from 1:1 the slower the engine needs to turn for a given speed. Am I totally off??

Brad

 

Since this thread was started there have been a few developments that have occurred. Both have made converting to a V12 to manual, easier, cheaper and safer.

Tremec released a new version of the TKO called the TKX. IT's lower cost, smaller, lighter and way easier to fit. It also shifts positive just like the T56 Magnum and since there is almost no reason to have a 6th gear on the V12 this new compact TKX is the way to go! Also the modified bell housing is easier to source for use with the TKX too.

BTW i do conversions but I don't sell parts becasue there is ZERO chance a DIY'r doing this for the first time with a box of parts can get the same results as an experienced installer.

-

 

I'll quote Han Solo here: "Never tell me the odds!!!"

But thanks for your input.

Brad

 

Discovered a wonderful site on YOUTUBE ( Camp Chaos Chronicles ) whereas his newest videos show you how to build / install the Tremec 5 spd for a Jaguar V12 xjs. Walks you right through it. Great site, everything from injectors to rebuilding the V12. Another good site on YouTube regarding the jaguar V12 is Living With A Classic. Hope this helps.