BW12 auto transmission valve body

Hi Jag Lovers! I have read through a number of conversations regarding the above auto transmission. Frank_Anderson seemed to have the transmission sussed and I would appreciate hearing from him, or any knowledgeable person, regarding this particular BW12 transmission that changes too late even after all the basics have been done! (I even removed and stripped the transmission in order to check sealing rings, governor circuit through to front clutch, valve body many times etc etc) I have driven with a hand held vacuum pump, in order to trick the modulator, trimmed 10mm off the modulator pin, with the same trick in mind, but all to no avail. Up change from 1st to 2nd remains at about 3000rpm, on a flat road using minimum throttle. Does anyone have an exploded view of the valve body for this desperate, Dan?

See personal email.

John F. Quilter, Eugene, Oregon USA

Hey Bob, you’re the man for responding to a brother in need, and thank you! Sadly I have that Automatic Choice page! It helps for the tranny line up but the valve body is not exploded! I am busy negotiating with John Quilter, who worked for Jaguar North America, and he has those precious pages in a gold plated book, which he plans to photocopy and email to me! Kind Regards Dan Varoy

Hi again Bob! Just in case you didn’t see my reply on the forum?
“Hi John and the team of Jag Lovers. Just to let you know that the problem on that BW12 auto transmission was solved after John_Quilter kindly copied and emailed me vital transmission info, particularly the exploded view of the valve body. Someone had been there before us and two vital 3/16” check balls were omitted in the main body, between the two separator plates.
The exploded valve body view showed the problem immediately and even though finding two 3/16" balls was difficult in this metric society of South Africa, once installed and reassembled, that tranny was a peach! Thank you John and God Bless America"

I looked in the Mark X, XJ6 and XJ12 parts books and all they show is variations of this.
I guess they didn’t expect anybody to ever take it apart.
Anyway glad to hear you got it solved.

Thanks Rob, the spares shop only want to sell a complete body! We fix it guys, might have done one of these valve bodies way back when, but since then too many solenoids, speed sensors, TCMs and wiring looms have short circuited the memory cells! Well mine anyway! Great to know that the “library” remains open even when the search engines failed! Regards again

Dan, your reply today, less than 24 hours after receiving my WSM copies, just makes my day! Glad to have been part of the solution.

John F. Quilter
Eugene, Oregon USA

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something that may help for information! Wikpedia BorgWarner drivtrain !

the BW 12 automatic transmision was originally designed and manufactured by BORGWARNER and FORD in USA!
and has been used in all makes of machines/vehicles! an amazing device!

ALSO, Borgwarner developed the new rage trans,(DCT), Dual.clutch /Porsche/ Volks wagon Group!!
and now again all types of vehicles!
also built in many countries around the world!

I have many details of the various valve bodies of BW8, 12 and Ford FMX trans

a lot of this is gleaned from the Studebaker forum, which have BW8

in that forum it details the Ford FMX is almost identical to the BW12

Hey John, as I mentioned to Rob, cool to have the library a few key strokes away! :smiley:

Now you tell us Tony! I grew up on Borg 35s and Torqueflites in Wellington NZ, so the BW12 felt like the back of my hand, except for those missing 3/16" balls! Agree with Ron’s amazing device sentiment! Thanks, we have your number for next time!

Thanks for that info Ron! Seems Borg Warner have been busy boys! :smiley:

you did well

are they item 5…shown in my factory FSM S1 XJ6 ?



In fact, this site is an invaluable resource if you want to work upon your BW 8/12 auto trans

Yep, no 5! Except in my body there was only space for two! The lower extreme right ball had no place. The valve body might have been changed with that from another application over the years! Regards