4 speed Trans Tunnel mods

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Kiddart1

Kiddart1

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I have a 4 speed trans tunnel in my demon, has anyone put a 6 or 8speed Automatic trans in an A-body with a 4 speed tunnel. do i have to open any areas up or can it be left alone. I know i have to make a mount i just dont want to cut the floor. I will be happy running my 727 if need be.

let me know if anyone has done it. I have only ran 727 and 904s behind the gen 3's
 
Last edited:
Kiddart1 said:
I have a 4 speed trans tunnel in my demon, has anyone put a 6 or 8speed trans in an Abody with a 4 speed tunnel. do i have to open any areas up or can it be left alone. I know i have to make a mount i just dont want to cut the floor. I will be happy running my 727 if need be.

let me know if anyone has done it. I have only ran 727 and 904s behind the gen 3's
Click to expand...
I put a T60 in my 72 Demon and had to fabricate a new tunnel.

IMG_0315.jpeg
 
The 4 speed tunnel doesn't give any extra room for a T56 so you will do most of the same work as an auto. The T56 is too tall and wide to fit regardless of which tunnel you start with.

@goldduster318 did this conversion here and started with a 4 speed tunnel.

img_20180910_131341355-jpg.1715222331



Pretty sure an 8HP will be similar, but it depends on motor location. I think @HemiDenny got an 8HP to fit under the floor with his COC kit but the motor is forward a little and down to do it if I remember correctly.

Here is @4.7Light's 8HP swap, he cut the whole tunnel out. Can't say for sure, but I really don't think a 4 speed tunnel will make that install any easier either.

img20240421134424-jpg.1716239746
 
DionR said:
The 4 speed tunnel doesn't give any extra room for a T56 so you will do most of the same work as an auto. The T56 is too tall and wide to fit regardless of which tunnel you start with.

@goldduster318 did this conversion here and started with a 4 speed tunnel.

img_20180910_131341355-jpg.1715222331



Pretty sure an 8HP will be similar, but it depends on motor location. I think @HemiDenny got an 8HP to fit under the floor with his COC kit but the motor is forward a little and down to do it if I remember correctly.

Here is @4.7Light's 8HP swap, he cut the whole tunnel out. Can't say for sure, but I really don't think a 4 speed tunnel will make that install any easier either.

img20240421134424-jpg.1716239746
Click to expand...
Mine is based off a six speed transmission install motor trend article. The very transmission your installing
https://www.motortrend.com/how-to/install-tremec-t56-6-speed-plymouth-duster-mopar/
 
I will add this your going to have a blast in that car track mode on 8HP70 8 speed auto is stupid fun. The car with 450 plus HP for little old 360 is stupid fast. I get a good laugh out of twin turbo v6 Explorers and other modern crap and I can walk off. I need a roll cage now the car is way to fast! Even with 2 x Frame connectors and trans is a bit heavier and new interior car is heavier. It will flat out blast a 360 727 car no comparison with what I had. Hear ratios matter and of course the shift maps and stays in the power band never falls out. Manual shift with the ZF it drives like a manual simply magic.

If I didn't have bad hip I would have done the 6 speed manual.
 
I absolutely don't recommend doing mods and just taking the top of the crossmember out or welding some piece of flat plate, that does absolutely nothing at all. You need a 3D shape line in my car. The car has no stiffness then and its even worse with Torsion Bars. That crossmember is very important.
 
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