Gen 3 Hemi Trans advice

[amvenne]

I'm swapping a Gen3 5.7L in to my '66 Charger. Curious what recommendations you guys have for an automatic tranny. It's not a race car so I'm not concerned about max HP/speed. Just an occasional cruiser. I also have the interior put back together already, so would prefer to avoid modifying the tunnel if at all possible. Thoughts?

 

[wish4hemi]

904 automatic. Cheap, lightweight, no cutting required, stronger than people give it credit for.

 

[70chall440]

I second that but would add that any SB 727 will work as well as an A518 (if you can find one). The 518 has OD which is pretty nice.

 

[493 Mike]

If available I would go for a A999. It is the beefiest of the small TFs.
Mike

 

[amvenne]

Thanks guys. Right now I've got a lead on either a 4L60e or an 8HP70. I know the wiring and computers will be different with those but, more importantly, do any of you know how much modification will have to be done to the trans tunnel for either of those?

 

[furious70]

8hp requires opening and widening the tunnel

 

[70chall440]

Thanks guys. Right now I've got a lead on either a 4L60e or an 8HP70. I know the wiring and computers will be different with those but, more importantly, do any of you know how much modification will have to be done to the trans tunnel for either of those?

From what I have seen a considerable amount, those are large transmissions requiring a significant amount of effort to get them in.

 

[65rbdodge]

I’m pretty sure any auto transmission besides a 727/904 will require tunnel mods. The 500/518-42/46rh/re and have a bigger tail shaft section where the OD fits. The modern transmissions that are behind gen 3 hemis are even bigger.

 

[TTSaleen]

For ultra simplicity one of the older 3 speed style autos (904/727) would be easiest.
However if you are planning the modern 8HP (dodge) you will need a few things to make it work including mount, crossmember, custom driveshaft, correct shifter and standalone computer system and harness to run it. The tunnel will require cutting and opening up to accommodate the much larger 8HP transmission.
I have the NAG1 5 speed auto in my swap (donor car was 2006 Dodge Charger).

I used the Hooker Blackheart pieces to mount it.
I used the Sound German Automotive transmission controller and harness kit.
I used the stock 2006 Dodge Charger shifter.

I originally used the Hotwire Auto harness kit to run my HEMI swap.
When my factory 2006 computer died, I pulled all that out and installed a Holley Terminator X computer system.

Good luck!
Ryan

 

[Sixpactogo]

If you don't want to modify the tunnel, you are pretty much stuck with the 904. When I updated my 68 Charger with a 6.1 Hemi, I wanted the extra gears for fuel mileage so modifying the tunnel was the only option I had. Back in 2014, no one was using the NAG 1 because of all the issues with management which have now been dealt with. I used the 545RFE (truck transmission) because of the two extra gears and it doesn't need any special regulation. I had to raise the tunnel 2.5" and widen it a little to make things fit but I am happy with the results. My console is higher than normal but no one notices the difference. It don't have the best gear ratios but it provides me the fuel mileage (+20) I wanted and the only time down the track it ran a 12.88 @ 103 mph. With the 3.23 sure grip, the RPM's are at 1700 at 70 mph.
I didn't like the looks of that ugly fly by wire gas pedal so I used the factory pedal and a truck bell crank to run the throttle. With the hood closed, the car looks completely stock. You didn't say what your final expectations are so no leadership here. Just some reasoning behind mine.

 

[Runcharger]

I bought a 15 Ram with the 6 speed in it, it was pretty disappointing as these engines aren't as tractable as an LA or B engine are. I ended up trading for an 18 with the 8 speed and it is much more drivable. IMO you need lots of gears with these engines. and 3 speeds and maybe even 4 speeds would not be enough.

 

[amvenne]

For ultra simplicity one of the older 3 speed style autos (904/727) would be easiest.
However if you are planning the modern 8HP (dodge) you will need a few things to make it work including mount, crossmember, custom driveshaft, correct shifter and standalone computer system and harness to run it. The tunnel will require cutting and opening up to accommodate the much larger 8HP transmission.
I have the NAG1 5 speed auto in my swap (donor car was 2006 Dodge Charger).

I used the Hooker Blackheart pieces to mount it.
I used the Sound German Automotive transmission controller and harness kit.
I used the stock 2006 Dodge Charger shifter.

I originally used the Hotwire Auto harness kit to run my HEMI swap.
When my factory 2006 computer died, I pulled all that out and installed a Holley Terminator X computer system.

Good luck!
Ryan

This is perfect Ryan! I'm leaning towards a NAG1 as well. I saw the Hooker Blackheart pieces and those look simple enough. I was also thinking stand-alone computer system as well, though I havent picked one yet. The shifter wasnt something I had thought through yet...

 

[Don selleck]

the 8 speed is bad *** though

 

[67Charger]

I'll just weigh in here. I'm running an A904 behind my 5.7 with the 6.4 VVT/non-MDS cam. It rips on top, thought a little laggy on the bottom. At the strip, the lack of a good low 1st gear is a little sluggish off the line. I've killed 2 of them, but I am also spraying it with about 150HP of N2O and ticking the 11's with a tight 2800 stall 10" converter and 3.55's. As a cruiser, it is just fine, it's the strip that kills them. I'm going to an A500 very shortly here. I don't want to cut up the car, but I need more rear gear to get moving, but less gear for cruising without spinning 3200 at highway speeds.

 

[amvenne]

Coming back to this one- I've decided I'm going with NAG-1. The required modifications look relatively simple so I'm comfortable there. I've also managed to score a G3 hemi with the tranny, wire harness, computer and fuse panel. I think this should make the whole swap much more simpler. My next challenge will be the electrical. Anyone seen an easy solution to switch from the OEM fuse box to the modern one from my donor vehicle?

 

[Dennis H]

ZF A8, hole the size of the Ocean. I would let the Hoop and Rubber Band Crew handle that.

 

[Dave6T4]

I would never run a 904, if I could find a small block 727. These were used in a lot of applications especially 340/360 cars and pick-up trucks. If you compared the clutch contact area between a 904 versus a 727, it only makes sense to use the bigger transmission. Lot more torque capacity. As others have said, the O.D. versions of these require floor pan surgery to make them fit. The hard part is cutting into the torsion bar crossmember, and rebuilding it without compromising strength.

 

[furious70]

Holley makes the kit to alter and reinforce the cross member for the nag1 or TF8

 

[furious70]

Coming back to this one- I've decided I'm going with NAG-1. The required modifications look relatively simple so I'm comfortable there. I've also managed to score a G3 hemi with the tranny, wire harness, computer and fuse panel. I think this should make the whole swap much more simpler. My next challenge will be the electrical. Anyone seen an easy solution to switch from the OEM fuse box to the modern one from my donor vehicle?

HOME

www.hotwireauto.com

Can help

 

[Dennis H]

If the Nag1 came in the 06 or so Hemi Charger, take a ride first to make sure you like it. I’d call it just ok.