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M12

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rsrguy3 View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote rsrguy3 Quote  Post ReplyReply Direct Link To This Post Topic: M12
    Posted: Jan/30/2020 at 9:27pm
So.... The resolution is to get the 71 Z-code on the road this year! I have a 727 from a 73amx and the original m12. Both need to be rebuilt, the 727 needs to have the crank machined. I think the TF weighs less but what else should I consider? 
1. Which is tougher
2. Is there a way for me to find the parts and rebuild it myself? Any vids? 
3. Are there any substantial reasons to go with the TF over the m12? 
4. Should I use the billet steel flywheel/flexplate and bell spacer I have or try to find an originalflex plate. 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote rsrguy3 Quote  Post ReplyReply Direct Link To This Post Posted: Feb/01/2020 at 9:06pm
No opinions? Odd
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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: Feb/01/2020 at 11:58pm
Its your car how much do you want to do to it? The m12 is not a bad transmission, and would be far the less expensive way to get your car back on the road. A 727 is more durable, chrysler put it behind the 426 hemi and 440. More performance parts are available for it. One example is no valve body kits are made for the m11 or m12. I still will say the m12 is not a bad trans. The only way I would put a 727 in it would be to change the crankshaft to a 72 or newer crank that is made for a 727.The factory spent tons of money designing parts and a bunch of hand made adapters is just asking for problems. Parts for both are not hard to find, m12 bands will need to be relined, several different linings are available.
1970 390 4speed Bittersweet shadow mask AMX
1970 Amx missing most everything, or in a box
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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: Feb/02/2020 at 12:09am
I bet it will cost as much for modifications to put a 727 in it than rebuild the m12.
new driveshaft
new yoke
new mount
new cooler lines
TV linkage-dip stick
shifter linkage
adapter-or change crank
1970 390 4speed Bittersweet shadow mask AMX
1970 Amx missing most everything, or in a box
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rsrguy3 View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote rsrguy3 Quote  Post ReplyReply Direct Link To This Post Posted: Feb/02/2020 at 9:21am
That helps quite a bit thank you. 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote tomj Quote  Post ReplyReply Direct Link To This Post Posted: Feb/02/2020 at 10:33am
torqueflite will not attach to 1971 motor. bellhousing patterns changed in 1972.

is there a V8 exception to this?

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turbo View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote turbo Quote  Post ReplyReply Direct Link To This Post Posted: Feb/02/2020 at 10:34am
M12 is light duty, rough shifting trans.  Normal driving?  M12 will work.  Any performance at all?  Forget it......
they call me Capt Fun.......!
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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: Feb/02/2020 at 10:38am
Originally posted by tomj tomj wrote:

torqueflite will not attach to 1971 motor. bellhousing patterns changed in 1972.

is there a V8 exception to this?


gen 1 and 2 amc engines have the same bell housing bolt pattern. The crank shaft flange changed in 72 so they could use a torque flite trans

my screwup, gen 2 and 3 are the same.


Edited by 1970390amx - Feb/04/2020 at 10:25pm
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 White70JavelinSST Quote  Post ReplyReply Direct Link To This Post Posted: Feb/03/2020 at 11:03am
Bellhousing patterns did not change on the V8 engines.

I6 Bellhousing did change around that era (72 I think) to the same bell pattern as the V8 engines have.


Added this a day later:

The post after this one is correct. I should have referenced 67 and newer engines. I regret that I have become accustomed to discounting the first gen engines in my conversations as I have no experience with them at all.


Edited by White70JavelinSST - Feb/04/2020 at 12:09pm
70 Javelin SST, second owner, purchased 1972
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Buzzman72 View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Buzzman72 Quote  Post ReplyReply Direct Link To This Post Posted: Feb/04/2020 at 6:06am
Originally posted by 1970390amx 1970390amx wrote:

gen 1 and 2 amc engines have the same bell housing bolt pattern. The crank shaft flange changed in 72 so they could use a torque flite trans

I beg to differ. Gen 2 and 3 have the same bellhousing pattern. The Gen 1 250/287/327 bellhousing pattern was different.
Buzzman72...void where prohibited, your mileage may vary, objects in mirror may be closer than they appear, and alcohol may intensify any side effects.
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