Regards

Dono

Personally, Id leave it alone as parts can be difficult to find..

Just manually shift it..and its better if you do manually shift it

Unfortunately a transmission swap is difficult because of the small pilot bushing crank in the 68 390. I wonder if a custom torque converter could be made so the crank would need to be modified? 

Regards

Dono

There is some info about the vacuum modulator adjustment in this thread. Not sure what effect, if any, it would have on the full throttle shift point.

https://theamcforum.com/forum/bw-m11b-shift-kit-parts-or_topic110887_page1.html" rel="nofollow - https://theamcforum.com/forum/bw-m11b-shift-kit-parts-or_topic110887_page1.html

It also states going to a modern band material with more friction and oil distribution grooves will reduce heat generated substantially.

 

Isn't there a note in the Owner's Manual, that a BW, in the "2" position will automatically upshift to 3rd at 70-something MPH?

In the Jaguar Forums it talks of the odd shift points of an M12.

1 is 1st and it will stay there until you blow the engine.

2 is 2nd start and 3rd at 60 to 80 MPH, depending on which member is talking.

D is 2nd start and 3rd at approximately 30 to 40 MPH

Big no no is to downshift to 1st.

This does make sense as many automatics in the 60's if put in D would start in 2nd unless the throttle or vacuum forced 1st. Very effective in snow to start in 2nd!

If this is how your M12 works, I'm guessing all is well. For drag racing, start in 1st and move 2nd at your preferred shift RPM.

Only posted what I've read or have documentation on.

I would think a current owner or someone with a lot better knowledge of the transmission could verify what I've posted.

The AMX and Machine with the floor shifter seems to have a modified M12 valve body. Higher oil pressure (different spring) and more flow (enlarged holes) for faster shifting. Again, that would have to be verified. Very sparse on the details of the modifications. Not much documentation out there to find.

https://www.hemmings.com/stories/article/jaguars-sports-car-grows-up-1971-1974-jaguar-e-type-v-12-series-iii" rel="nofollow - https://www.hemmings.com/stories/article/jaguars-sports-car-grows-up-1971-1974-jaguar-e-type-v-12-series-iii

Not sure, but there was a TSB on this stating it will upshift at ~5000 RPM, and a note that said something like "only someone crazy would drive like this"

Edit: no one in their right mind would drive like this

The M35, the little air-cooled job, has the same D2 D1 L pattern. I forget the shift points, but moving the lever to L is suggested to put it into LOW (1st) below X MPH, and into MID (2nd) below Y MPH. I forget X and Y. I use this climbing hills, eg. to drop into 2nd on a long grade instead of lugging.

Those are some easy things to try. 5100rpm would be perfect ('68 390, 10:1, 268H, and Hooker headers). 

Regards

Dono

Correct, but the D2 position was the "first" D position (right after Neutral). Most people unfamiliar with the trans pull it into that position and assume they have a two speed trans. The "middle" of the forward drive ranges shifts all three gears. D2 wasn't intended just for slippery surfaces, but was intended to be the main forward drive position, with D1 used only on hills or when loaded. The idea was to start in a higher gear and let the torque converter get you started so the car would up-shift to high as soon as possible. It was supposed to be an economy measure, but only if you start slow. If you start quickly (just about have to in today's traffic!) it's better to pull it into D1 all the time. The engine will work a little less getting up to speed, and economy will actually improve over trying to get up to speed quickly by starting in second.

There is a big difference in the way people who came up in the 40s and early 50s drive and the way we drive now! Most don't realize how different people used to drive during different decades. When cars first started hitting the road in the early 1900s you had to be part mechanic, and if you drove 50 miles in a day you were driving a lot! Most people drove no more than a couple hundred miles a week, if that. 10,000 miles would wear half the parts on a car out at that time! Even in the 60s 100K on a car meant that it was pretty much worn out and it was hard to get much if you traded it in or tried to sell with over 100K -- I remember my father and grandfather stating that their car had 80K on it -- time to start looking for another! Now 200K is just good broke in, you have at least another 100K to get out of it! My 2003 Toyota Tundra work truck is a bit beat up now (I do home repairs out of it, so always hauling something!), but it has 264K miles on it and shows no signs of slowing down. Only regular maintenance items done to it. Might have to replace the power steering rack or pump soon... I have to put fluid in it every couple weeks now (I average 250-300 miles a week). Both are original to the truck, never replaced!

When I got my drivers license in 1970, before I got my '57 Rambler 20-series on the road I drove my dad's '61 Rambler Classic with the 196. It would hold L range to 60 MPH if you floored it, but not upshift until you selected a different button. In D1/D2, the car still topped out at about 90, which was sufficient for a new driver with a high lead content in the right foot. [The '57 Rambler with the 250 V8 and Hydramatic would top out at 120 MPH @ 6000 rpm, and would do it until you ran out of road to run that fast.]

As a teenager in that '61, I primarily used the D1 position. Dad primarily used D2. Gas was 32.9 cents a gallon then for the name-brands, and so we never paid that much attention to whether my way used more gas.

Lol, the owner's manual for my 1960 American suggests using D2 for most driving, and D1 when you need extra power! This was a flathead with the cast-iron M8 transmission -- so yeah, you might want "extra power"!

Regards

Dono

I had a Ford C4 that we played with the spring in the governor until it would shift 1-2 under WOT at 5600 rpms and 5400 rpms on the 2-3 shift. We spent weeks and weeks trying to get the rpms up on the 2-3, but finally my friend that owns the transmission shop told me that's as good as you're to get.

However like the others have already stated if you want to do high rpm WOT shifts and expect it to live you probably need to remove the BW12 and replace it with a different model transmission (727, TH400). While I have both in my opinion the TH400 is the easiest from the kickdown standpoint since it uses a switch and you don't have to deal with all the linkages require on a 727. 

Good Luck,

Tom

The trans won't shift into first over a certain speed (20 mph or so) for safety reasons. Dropping into first could damage the trans or slow the rear wheels suddenly, having the same affect as locking the rear brakes and could cause one to lose control of the vehicle. All the Borg Warner autos have that feature -- I'm pretty sure even the modern derivatives do, like the AW-4. Once speed drops below the threshold speed (I'm not sure it's 20 mph... but close) it will drop down into first gear while moving.

Regards

Dono

Regards 

Dono

Regards

Dono

I’m sure someone back in the day had the specifics of this exact governor modification nailed down, but it’s since been lost in the mists of time and would need to be gone through all over again. Which is a shame, because I doubt anyone would bother with these transmissions since everyone is convinced they’re boat anchors. So the external modulator adjustment is the de facto way to go.