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M-12 to GM 700R4 Swap

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6t8amxetc View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote 6t8amxetc Quote  Post ReplyReply Direct Link To This Post Posted: Apr/04/2023 at 7:44am
Originally posted by SC397 SC397 wrote:

Originally posted by 6t8amxetc 6t8amxetc wrote:

Originally posted by SC397 SC397 wrote:

Originally posted by Gadgetman1 Gadgetman1 wrote:

I’m not understanding your use of the word “pilot”. 
The torque converter on any engine has to locate or "pilot" to the center of the crankshaft.  The torque converter bolts just fasten the torque converter to the flex plate.  The torque converter bolts do not center the torque converter to the crankshaft.  The 390 engine has a small 1 1/4" pilot hole in the back of the crank shaft just like all of the AMC V8's up until 1972.

 I don’t know what a 727 is.  It the transmission that AMC used from 1972 and later.

All of these adapters are not listing the 390 engine.  They won't but the 360 and 401 have the same bolt pattern as a 390

This is about as clear as pea soup to me.  What I’m trying to do, is upgrade to a more modern transmission that allows for less RPMs & better fuel mileage on the highway.
There is no direct kit to do that without some engineering.


Well maybe one of you should just buy the kit I have listed here for sale and I'll send it to Rick so he can engineer/machine a torque converter spacer! Then everyone can know the answers!!
I'm sure Rick has lots of free time for that little project. Smile 

Correction... He should buy the 904/727/A500/AW4 adapter kit and and find a A500 or AW4 out of a 4L Jeep and directly bolt it to the 390 and not dick around with a GM transmission that is made for a GM engine.
Common sense people..


That may be a good option. Some people may prefer the choices and selections afforded by using a very common transmission! Options are usually a good thing. 


Edited by 6t8amxetc - Apr/04/2023 at 7:46am
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Buzzman72 Quote  Post ReplyReply Direct Link To This Post Posted: Apr/04/2023 at 7:55am
If you're dealing with a 290 or 343, you swap in a '72-up 304 or 360 crank and use the Novak or Advance Adapters kit to install the GM transmission. But the 390 is different because '72-up 401 cranks are already drawing premium money due to their rarity, compared to 304/360 availability.

And with a dwindling number of '68-'70 390s [and an already small number of '71-only 401s], the market simply isn't there to PROFITABLY design and sell a 390-to-THM adapter kit. It's a niche product for what's becoming a niche engine.

Not a bad engine, mind you. Just an engine that was never produced in GM, Ford, or Chrysler numbers to start with.
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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Post Options Post Options   Thanks (0) Thanks(0)   Quote RandyB Quote  Post ReplyReply Direct Link To This Post Posted: Apr/05/2023 at 7:28pm
And people wonder why users leave this forum
Randy B
68 Javelin SST 343
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Post Options Post Options   Thanks (0) Thanks(0)   Quote jblue1555 Quote  Post ReplyReply Direct Link To This Post Posted: Apr/05/2023 at 8:36pm
And the truth makes someone triggered again. He is correct in his statement which may not please some but that’s pretty common. If some had been around with no new products at all and nothing but who knows who , who might have that part no web to communicate they would be thankful
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Gadgetman1 Quote  Post ReplyReply Direct Link To This Post Posted: May/27/2023 at 3:50pm
I stepped away from this topic for awhile to get my engine ready for a rebuild.  So, you’re saying that there may be other transmissions that will bolt up better that have an overdrive? Which ones & what make & years?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Trader Quote  Post ReplyReply Direct Link To This Post Posted: May/27/2023 at 4:05pm
All the information is posted in this thread. Just start at the beginning and work through it to make a list. Rehashing the complete thread from the beginning is likely not going to happen.
This is not meant to be sarcastic, but realistic.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Gadgetman1 Quote  Post ReplyReply Direct Link To This Post Posted: May/27/2023 at 5:23pm
Never mind then - trying to make sense of this thread is like scuba diving in a mud hole! 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Thikstik Quote  Post ReplyReply Direct Link To This Post Posted: Aug/18/2023 at 9:57pm
So the 46RH and the 46 RE IF , from a Grand Chero 4.0, would fit a 1975 258? and would crank pilot holes and flex plates be compatable?  
Regarding the designations, does the A-500/A 518 indicate that its a Chrysler trans with a non AMC bellhousing?




Edited by Thikstik - Aug/18/2023 at 10:03pm
75 gremlin x, jeep 4.0 headed 258,
264H Cliff cam, intake,header. 390 holley. I want a 282 VAM motor!

AC/PS/PDB.

72 AMX , 304 2bbl, 3speed, now disks...probably will sell, want an automatic /AC.

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Post Options Post Options   Thanks (1) Thanks(1)   Quote purple72Gremlin Quote  Post ReplyReply Direct Link To This Post Posted: Aug/19/2023 at 6:53am
Originally posted by Gadgetman1 Gadgetman1 wrote:

Never mind then - trying to make sense of this thread is like scuba diving in a mud hole! 
No, I  understand it fine.   Its alot of you guys asking why it wont work.
And its very simple.   It all come to this.   1966 to 71 engines have a flat crankshaft flange. Which means there is no hub for the torque converter to go. The Borg Warner has a hub that is the size like a standard transmission. 
1972 and later use the chrysler TF. Which uses a normal hub on the crankshaft, and the converter has a place to go in.and the flexplate is also different. 
Now if you dont understand what I said about this,  then you have no business even working on a car then.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Gadgetman1 Quote  Post ReplyReply Direct Link To This Post Posted: Aug/20/2023 at 1:16pm
I’m using a 401 crankshaft with a 72 Chrysler transmission, which solves my problem.  It’s sad that everyone is all talk, but no one is fabricating parts to retrofit newer transmissions.  It’s also sad that every reproduction part I have purchased so far is absolute crap!
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