Need advice from MK2 S-type owners please. Any photos would be a big help.
I got a 4 synchro gearbox JBN7307 with overdrive (28/60572) to pair with my 1987 4.2l XJ6 fuel injected engine. replacing a BW-66.
1. How do I wire the OD engagement switch? 1.(a). Is it on the Colomb, dash or shift lever?
2. How/where do I wire the reverse switch? 2(.a). Engage only in 4th switch? Photos if able, please.
3. Do I make the park/neutral into a clutch is depressed switch or should it be a start only in neutral switch?
4. Is the Eletronic transducer able to be swapped into the gearbox for the speedometer? 4.(a). Will I have to swap to mechanical speedometer? 4.(b). Right angle drives and calibration?

 

I assume this is for your Aristocat.
1. Where you like. The Mk2 has it on the column, the XJ6 on the gear knob, 1950s Jaguars on the dash. I'd go for the column.
2. The reverse switch on the top of the gearbox connects to the reversing light on the back of the car. 2a The 4th gear switch is in the overdrive circuit to prevent engaging overdrive in any gear other than top.
3. Unless there are some rules in your state that force you to do otherwise, I would leave it out.
4. It's not obvious to me how the transducer could be swapped, but it is an attractive mod. 4a - a mechanical speedometer would be straightforward, but I guess it wouldn't match your tacho. Smith's mechanical speedos have turns per mile on the face. Most from Mk2 and S types will be calibrated fir a 3.54 (auto trans and non overdrive) or 3.77 (manual with overdrive) axle ratio.

I hope that helps

 

Peter,
Yes, that helps me getting started for the Aristocat build. I guess that I would have to put the Park/neutral relay to earth, so that it will start in any position and not worry about the clutch. Will also have to source a column switch (nice looking, if able).
Will need to look for the wiring diagram for the gearbox section of the MK2 S-type, to get reverse lights and OD engagement correct.
My diff is a 2.88 but will still try to figure out speedo transducer although I would like to get a new/referb speedo with zero miles on it, as the drive train and axels will all be refreshed along with brand new chassis.
Thanks for the reply,

 

Have you tried to fit the electronic transducer on the gearbox? From memory, it's a very similar type of fitting to the end of the Mk2 speedo cable. You might just be lucky. And if not, it might be possible to improvise an adapter.

 

If it all gets too hard for a speedo then I suggest you consider a GPS speedo.
Far, far more accurate than most automotive systems.
I have been using them for over 10 years.

 

Depending on the overdrive ratio, you might consider changing the rear axle ratio too. When I put a 5 speed into my S Type, it really lugged in overdrive at normal highway speed and wasn't happy. I changed the 5th gear ratio from 0.63 to 0.73 and the car was much happier.

As rule of thumb, I wouldn't want the overall ratio ( od x rear axle) to be smaller than about 2.50. My S Type actually ended up at 2.75 (3.77 axle x 0.73 OD), originally it was 2.37 and that was too steep. Maybe if you cruise at 90mph that ratio would be fine, but at 70 mph it wasn't.

 

... and at the other end of the scale, you don't want an over all ratio much below 9 in first gear even for a lightweight.