Can you fit 'Sport Mode' to the Gearbox on an XJS V12?
 

Hi Guys

Is it possible to fit 'Sport Mode' to the Gearbox of an XJS V12

Would that even be a desirable option to have?

OB,

The late XJS V12 do have 4-speed boxes with Sport Mode options. As regards the early 3-speed boxes, you could do a lot worse than just change the modulator then tweak it to change the upshift points. Apparently, it can really change the driving experience and is a really cheap mod.

Paul

A B&M adjustable modulator works wonders as PTJS said. So does lightening the governor. So does sticking it in 2 and leaving it there (the cheapest option)!
All sport mode does is alter the shiftpoints, ie: make an autobox hold the lower gears longer to higher revs.
Greg

Transmissions with sport mode are all electronic and the sport mode changes the shift and pressure control maps, it may also change torque converter lockup.

I would steer clear of shift kits, these usually make the 1-2 shift painfully hard.

Not 100% about the S Mode... The X300 4.0l and 4.0SC both had the ZF 4hp24 or 26 (can't quit remember what shaft size but it wasn't the 22) but that was fully mechanical. The S still worked by a small modulator inside the tranny.

Otherwise I agree. To get a properly working S Mode you will need a fully electronical tranny. Like the 5hp24 (as fitted to the NA X308 models) which has solenoids instead of mechanical valves etc.

@OB

To get a properly working S Mode, you'll need to do a lot of work. You'll want as said, a fully electronic transmission. This will require fiddling with the engine ECU, as these electrical trannies need a signal from the ECU to shift up or down a gear. Like in the case of the 5hp24. As the 4 speed in the 6.0l was from GM, and as I am more familiar with ZF and AW trannies, I don't know how they managed to incorporate a signal from the ECU to the TCU for upshifts...

You then would want, if ypu don't take the GM box, an adapter between tranny and engine to mount it, custom linkages etc.

A lot of work for a Button that only Lifts the standard normal shift points. In the X308 it keep it in gear just a little longer and will prevent upshifting at lower speeds. For example the 5hp24 shifts in my 3.2l at 50 kph into 5th speed. In S Mode it will keep 4th. It will more commonly use the kickdown and increase fuel consumption...

Hi Greg

It sounds like a 'Modulator' might permanently increase the Fuel Consumption.

So may be better to stick her in 2nd when required.

OB,

Changing the modulator won't adversely affect your consumption per se. It's all done to how far down you press your foot and whether you use the additional upshift point capability

You'll probably find that just fitting a new modulator and even setting it as per the original change points will still give you a nicer shift change. Your original modulator is now 30 years old anyway. There really is no downside and they are not expensive.

Cheers

Paul

The X300 4.0SC XJR used the GM 4 speed same as in the 6.0L V12. The TCU in these did not talk to the ECU they were standalone.

+1 on the modulator.

My car runs the 4L60e which is an electronic version of the 700R4, great transmission with a very tall 4th gear. These are plentiful here in Aus although might not be so common in the UK. With the 3.58 rear gears the engine is spinning at 2100rpm @ 100km/h about 300rpm less than the TH400 and 2.88, very relaxed cruising.

They do talk to each other, there is engine speed into the TCU and a timing retard during shifts. The climate control ECM also talks to the TCU.

Wasn't that sure about the 4.0SC but the normal 4.0l also has a S Mode button and being a ZF tranny it is purely mechanical. At least for that time...

Sorry I didn't phrase this very well, what I was meaning was that the sport mode did not alter the engine mapping.

I don't think anyone even thought of that!?

People say their X308 R models alter engine, tranny, suspension etc. by pressing the S Mode button. Utter BS :D