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m12 shift kit

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tumbleweed View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote tumbleweed Quote  Post ReplyReply Direct Link To This Post Topic: m12 shift kit
    Posted: Mar/01/2014 at 9:31am
anyone know where to get a shift kit for m 12  ?
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1970390amx View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote 1970390amx Quote  Post ReplyReply Direct Link To This Post Posted: Mar/01/2014 at 12:28pm
No one makes one.The best you will be able to do is to shim the pressure regulator valve to add line pressure.
1970 390 4speed Bittersweet shadow mask AMX
1970 Amx missing most everything, or in a box
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Post Options Post Options   Thanks (0) Thanks(0)   Quote purple72Gremlin Quote  Post ReplyReply Direct Link To This Post Posted: Mar/01/2014 at 2:34pm
Transgo did many years ago, and I suspect they stopped because there was limitations, and 1970390amx is correct
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george w View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote george w Quote  Post ReplyReply Direct Link To This Post Posted: Mar/01/2014 at 10:11pm
AMC offered a shift improvement kit for M-11's and M-12's. There was a TSB on it and I'll look it up. The features of the kit were worked into production sometime in early 69 I believe. I'll look up the TSB and post it.
You can also tweak the vac. modulator adjustment to some degree to increase the line pressure, raise the shift points and to firm up the shifts. The adjustment screw is inside the stem of the modulator. It's a fine adjustment so it can take several turns to notice a difference.
If you crank it in too far the trans. will shift very harshly and very late or not at all if you go too far. It's easy enough to fine tune by road testing. AMC's posted line pressures in the shop manual were for typical passenger car smoothness and to get into high gear as soon as possible. To my knowledge AMC never released revised pressure specs for the performance applications.   
Long time AMC fan. Ambassador 343, AMX 390, Hornet 360, Spirit 304 and Javelin 390. All but javelin bought new.
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tumbleweed View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote tumbleweed Quote  Post ReplyReply Direct Link To This Post Posted: Mar/01/2014 at 10:19pm
cool,let me know.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote pacerman Quote  Post ReplyReply Direct Link To This Post Posted: Mar/01/2014 at 10:24pm
Here's another older thread on this topic:

http://theamcforum.com/forum/borgwarner-parts_topic11161_page6&SID=347323266zcfe86aac378c4dd41511373726852.html
Happiness is making something out of nothing.
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george w View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote george w Quote  Post ReplyReply Direct Link To This Post Posted: Mar/02/2014 at 8:00am
The TSB was dated Oct. 31, 1969. The subject was: Automatic Transmission Control Valve Design Improvement. M-11 and M-12 Shift Command Transmissions.

The description stated: "A revised control valve assembly, providing higher transmission pressures was incorporated, at the following transmission serial numbers, to improve transmission durability, especially for those drivers who expect to place abnormal demands on the units." "Transmissions built earlier are entirely adequate in performance for all normal types of driving." ( Keep in mind the mind set that AMC was was coming off of at the time the AMX was introduced. "Abnormal" and "normal" are the keys words here. What's abnormal for a typical Rambler granny is very normal for a performance car buyer )

The bulletin goes on to list the various transmission partnumbers and serial numbers where the mod. went into effect. It applied to both M-11's and M-12's

The "Shift kit" part number was 4488283. It increased operating pressures at the 1-2 shift point. There were three hard parts involved. Throttle modulator cutback valve, cutback valve spring and valve body end plate. Interestingly, there were no instructions or referrals ( at that time ) to make any transmission pressure setting changes. These may have come later. I don't know, someone would have to refer to the 70 to 72 shop manuals or to later TSB's as mine set of TSB's are only for the 68 through 70 model years. I did install one of these kits in a 68 343 AMX that I owned that is now owned by Ross Peterson. It did improve the 1-2 shift but it did not raise the 2-1 downshift kickdown point which was still somewhere around 20 mph. My 69 AMX with the same engine-trans. combo, which I still own, clearly has the revised transmission calibrations as the 2-1 forced kickdown speed was raised slightly ( to about 28-30 mph and both the 1-2 and 2-3 shifts are substantially firmer at any upshift speed. At full throttle my 69 will easily chirp the tires on the 1-2 shift and has a very positive and firm 2-3 shift. As a side note though there is a bit of a "clunk" when the trans. shifts back to first gear at about 5 mph on idle, closed throttle coast down.
Long time AMC fan. Ambassador 343, AMX 390, Hornet 360, Spirit 304 and Javelin 390. All but javelin bought new.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote 401MATCOUPE Quote  Post ReplyReply Direct Link To This Post Posted: Mar/02/2014 at 4:38pm
George...that "Factory" shift kit is awesome in the 68 AMX, I bought from you...I have had that "little" 343 engine chirp 2nd all the time under WOT...but only once in 3rd, right outside air temp, right humidity, empty gas tank, right phase of the sun/earth and moon!!!  It does improve and I guess I need to talk to a Texas friend to borrow the NOS one he has and try and reproduce it...I had it in my hands and 3 pieces kit is correct.
Ross K. Peterson
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Post Options Post Options   Thanks (0) Thanks(0)   Quote george w Quote  Post ReplyReply Direct Link To This Post Posted: Mar/02/2014 at 5:19pm
Ross,

I've caught a 2-3 chirp on occasion on my 69 as well. As you said, under the right conditions. You should also get a 1-2 chirp at less than full throttle too. Did you change to stickier tires ? I still have the Michelin 70 series on the original Rally's and Coker redlines on the chrome wheels. Neither have particularly good dry traction on acceleration.
There must have been other minor valve body or other internal changes though between the 68 and 69 transmissions as my 69 will kickdown or shift down into first at a higher speed than the 68 would. I don't know if this was a running change in 69 but I have to assume that all BW's had the mods in 1970 and on up. My next new AMC was the 73 Hornet X 360 which had the Torque Command Torqueflite so I don't know what advances were made between 69 to 72. The TorqueCommand had better responsiveness to kickdowns but didn't shift as firmly as the M-11's in both AMX's.
Are you back from Dallas yet ?
Long time AMC fan. Ambassador 343, AMX 390, Hornet 360, Spirit 304 and Javelin 390. All but javelin bought new.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote txamx Quote  Post ReplyReply Direct Link To This Post Posted: Mar/02/2014 at 5:55pm
Originally posted by 401MATCOUPE 401MATCOUPE wrote:

George...that "Factory" shift kit is awesome in the 68 AMX, I bought from you...I have had that "little" 343 engine chirp 2nd all the time under WOT...but only once in 3rd, right outside air temp, right humidity, empty gas tank, right phase of the sun/earth and moon!!!  It does improve and I guess I need to talk to a Texas friend to borrow the NOS one he has and try and reproduce it...I had it in my hands and 3 pieces kit is correct.

Ross,

I will be more than happy to send you the shift kit with the hope that you can reproduce it for others. I'll get it sent your way this week.

John B
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