We have seen many gen 3 conversions now, but I can't recall seeing anything but manual. I want to go automatic and it would be nice to use the matched original 5-speed auto tranny in my 70 cuda vert. I have the engine but no tranny yet. Before I get one I need to know if it will be room for it.

If you want a new 5 spd automatic, the best and easiest to use is a 545RFE out of a 2wd pickup or Durango. They are the only ones that have a slip yoke tailshaft, and can be run by the ECU from an 05 Dodge pickup. It's a BIG transmission, and it will require cutting the floor pan and torsion bar crossmember. It's not a swap that's for the faint of heart, but can end up nice. I'm putting a 5.7 Hemi and a 545RFE in a 70 Duster. If you don't want to cut the floor pan and crossmember, you could use a 518 automatic. They will bolt straight to a Gen3 Hemi with a thin spacer, and there is a flexplate available for the Gen3 Hemi to 727/518 convertors. Do lot's of research before plunking down a bunch of money. Good luck.

That tranny (SRT one) is a NAG1, it's a Mercedes tranny, completely different beast. From what I've read on here from another members post is that the NAG1 needs some sort of feedback from the ABS system to function properly because of the traction control system, so you would need to incorporate that as well, which doesn't sound fun. Go with the 545RFE, they're pretty bullet proof

WO23 has it right. The NAG1 has to take the input from all 4 sensors in the ABS and send that to the computer. It averages out the 4 readings to determine speed, and that is how the computer tells the transmission when to shift. That's kind of a gross oversimplification, but by all accounts I've heard...a NAG1 is a pain in the a$$ to get to work in an old car. If I can get to Photobucket, I will post pics of the 2 transmissions.

Here is my Hemi, and my 545RFE. I don't have any pics of the NAG1 that came attached to my motor. I deleted them after I sold it.

JD, what are your plans for the speedometer since the trans has no output for a mechanical cable drive.

That is on my list of questions to ask Chris Squire about when I call to order my harness. Dakota Digital made a nice gauge cluster for the Duster that was built on the show "Chop,Cut,Rebuild" I want to use the same thing, but I don't remember what they used for a transmission in that car. If that doesn't work out, I'll go to plan B and use an Autometer GPS speedometer. When I talked to Chris at the Mopar Nats this year, he said they about had it worked out on making cruise control work thru the ECU. They were perfecting a tone ring that goes in the tailshaft housing of a 545RFE, and it will send an output signal to the ECU. I would think if there's an output signal, it should work a speedometer also. I'm a good ways away from there yet,so that's kinda on the worry list backburner.

Also, if all you can find is a 4x4 tranny, there is a kit out there that supplies a tail shaft and all the necessary parts to convert it, can't remember off the top of my head who sells it though

Can you specify where and how the tunnel needs to be modified?
The gas pedal is very close to the tunnel, and also far left.
IS the 545RFE also high so the top of the tunnel needs to be modified?

There are a lot of threads about the trans tunnel mod, but most of them are installs of the 518 & 46 RH etc.

We need some more picture essays of the project for the Gen 3 trans install if you want to bother with it.

I don't have any pics yet, as I am not that far along in my swap. I have seen pics on the For A Bodies Only Mopar forum that show the tunnel mods. You have to split it up the middle, and also down each side to widen it out. It also has to be made a little taller. You also have to cut the top arch out of the torsion bar crossmember, and tie it back together with newly shaped steel after you get it cut wide enough for the 545 to fit. I plan on cutting the tunnel out around the transmission area, cutting the torsion bar crossmember, making a new transmission mount, and then making a new arch for the torsion bar crossmember. Then I will make the tunnel fit all that, and give adequate clearance around the 545.Nothing a few hours, a sawzall, and a mig welder can't remedy! No need to worry about the gas pedal, as you'll have to change that to a drive by wire pedal from a Dodge truck anyway.Gen3 Hemis don't use a throttle cable.