m12 shift kit

anyone know where to get a shift kit for m 12  ?

Transgo did many years ago, and I suspect they stopped because there was limitations, and 1970390amx is correct

cool,let me know.

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.

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 ?