Hi there,

Im currently looking at a good deal on an apparently tip top model 12 from an early v12 xjs. seeing as its a good deal and the auto in my series 3 is tired I thought I may as well buy it, change the bell housing and stick it in my 82 xj6. Ive been told that the model 12 is a stronger box then the later units and that the v12 version is stronger again with a bigger 1st gear clutch pack. ide imagine if the v12 drove it my old 4.2 shouldn't break it too easy.

Does this sound logical or am I taking a step backwards. Ive heard that they wern't the most refined boxes but like the idea that you can lock it into 2nd and that its fully cast iron and 'stronger'. I assume even if the shifts are agricultural its going to be a improvement on my slip, slide and slam auto. Ide also like to be able to tow a normal size trailer around, something my current box wouldn't like too much

Can i confirm that the torque converter will bolt up the same and has the same spigot, the bell housing from an 6 cylinder model 12 will fit and that the tail shaft is the same length. apparently the selector cable may be different, no biggie and the mount will need to be swapped?

Thanks,
Jay

 

Hi Jay, I don't know details about the fitting into a series 3, but I have a BW12 in my S1 XJ6(4.2). It was a bit agricultural when I got but replaced the vacuum modulator and played around with the adjustment screw on the modulator a bit,and adjusted bands,smooth as now.I also replaced kick down solinoid as I had a new one on the shelf for my Cherokee(Borg warner(Aisin warner) AW4) trans which is pretty much an FMX as well still being put new Jeeps in 1995. Says a lot for a design from early 1970's if your worried about its strenghts and weaknesses.
I bought an FMX modulator as they are more or less the same box,(ford part was cheaper)

Part No FVM-7000. Modulator FMX/MOD 12 Ford $31.20
Motospecs, Brisbane (07)3356 8499

They stock all trans parts and I think have stores in other states.

 

thanks for that, does your box change down when you go around corners and slow to sub 30 kph? my current borg warner refuses to change down accept if you a. boot it, or b.change down manually. its quite annoying having it hug third the way it does.

thanks
jay

 

Jay, I had a kickdown problem but traced it to a faulty micro switch on the throttle linkage. See previous thread on this(it has pics of switch)

https://www.jaguarforums.com/forum/x...pening-109454/

Here is a link to a new one on ebay.

Jaguar V12 XJ XJS Xjshe Kickdown Switch Inhibitior Switch | eBay

 

Just read you post again, Sounds like yours is kicking down ok if it changes when you boot it. Not changing when slowing down could be a vacuum problem,maybe an adjustment to the vacuum modulator( small screw inside where the pipe goes on). Or a vacuum leak in the line somewhere.
I can scan the page with modulator adjustments if you need it.

Clarke

 

Clarke,

The S3 6cyl has a BW66, with cable kickdown, and the adjustment of that cable at the rear of the engine is a PITA on a good day. Get it right, and they are a sweet transmission.

Aussie,

From memory (HAHAHAHA), I reckon teh BW12 will bolt up to the 6 cylinder block. Memory again (HAHA) is the pattern is the same, but it was 30+ years ago, so the fuzzies are as clear as mud.

The 12 is TOUGH, but 2nd gear band is the weak link.

The adjustable modulator is the only way to go.

The mounting should really be the same, and the tailshaft????, dont remember.

 

Ok so either way the bell housing should not be an issue. I can probably get a 6 cylinder bell housing anyway. What does worry me tho is if the torque converter spigot and mounts line up properly. Apparently the shift cable is different from S1 to S3?

Seeing as the box is from an v12 I would expect it to be fairly robust, but have heard about 2nd gear band. Is this a hard diy job? Ive heard these are easy to rebuild as far as auto's go. I would like to do some light towing with the car here and there as well. nothing over a 750kg probably (not that the tow bar would take much more, doesnt seem the most solid mounting system)

Thanks,
Jay

 

The snout of the '65/66 and the '12 convertor are the same size.

This I know coz the crankshafts between manual and auto are the same. Even the early V12's were the same size spigot hole. The V12 with TH400 is a different crankshaft, due to a larger snout.

This small spigot hole goes waaaaay back

I took a BW DG auto out of my 3.4 S Type and fitted a BW66, and it all bolted up sweet. I used a S2 "flywheel", as I simply did not like the S3 flex plate thing in those days. The starter motor was changed to a S2 unit as versus the old inertia throw style from the S of those days.

I really dont think you will run into too many snags.

The select cable is simply that, and apart from the ends MAYBE being different at the trans, I really cannot see anything other than a ball type connection, as is most any transmission select cable.

The shift control (kickdown to some) cable, is going to require some adaption at the throttle linkage end. A S2 donor linkage assembly will save many hours of language extension.