What are the options for getting an additional gear or two in an automatic transmission for e-body? Is surgery of the floor pan or cross member required to fit them in? My last project was a four speed, so never messed with automatic e/b body cars. Looking for possible options on a 70 Challenger.

Thanks.

I am using an A518 in my 70 Challenger.

I trimmed the case and made a rear mount of my own. A few pic are here in this thread.

https://board.moparts.org/ubbthread...4/re-four-speed-overdrive-automatic.html

I am using the whole Magnum 5.9 EFI, Trans wiring, and ECU from a 95 Ram Truck. If you want to keep your Carb there are controllers that kick the overdrive in based on vacuum and a couple other factors.

Good info here.
https://board.moparts.org/ubbthreads/ubbthreads.php/topics/140864/re-727-to-a518-swap.html

If you are gong Big block and want to use an A518 then here is some info.
https://board.moparts.org/ubbthread...8-overdrive-conversion-lots-of-pics.html

Otherwise Passon sells a 4 speed overdrive manual and there is always the gearvenders unit.

I’ve been running a 518 for 3 yrs and love it.
I built my own controller, not hrd.
PM me if interested in a simple pdf info package I put together.
Everything you need to know here:

http://www.cuda-challenger.com/cc/index.php?topic=84774.0

I have a 518 behind the Hemi in my 70 Cuda. No floor mods necessary. I didn't use a lock-up. There is a button on the console for activation and an adjustable vacuum switch for automatic OD drop out. I had A&A build a valve body for it.

Very happy with it and would do it again in a minute. My only regret is not doing it sooner.

To the Fellow who came up with the idea to notch the transmission case to make it fit: my hat is off to you. Used to be a significant butcher job before the case notch.

44rh for me: more power to the wheels.

There is also the Silver Sport 4-speed automatic... I believe its based on the GM 4L60 tranny... I've heard good things from pleased customers... I'm considering it myself.

Probably the best option if cost is not a factor, looking at $6k or more.
I’m all in at $2.5k you could go cheaper if you don’t want/need the automatic control.
Still by far the best money spent, car is so much more enjoyable to drive.
Only 2500 RPM at 80mph, 3.73 gears

Did I miss somewhere clarifying big or small block ?

If you are running a big block, I highly recommend TranzTech in Dubuque Iowa. They installed a 518 in my 65 C body and it is by far the best thing I have ever done for that car as far as drivability. I'm running 496 ci around 500 hp and so far it is doing well ! Just can't say enough about their work.

My install was a little complicated since I first had to convert the column from cable shift to linkage etc. (One year only) they worked with all that and everything works perfectly !

Running a 46rh ,, 518 in my 68 Charger, yes I know its not an E body :), 512 lowdeck, it is one of the best things I did to my junker, I had to trim the upper part of the torsion bar x member & build a custom trans x member. I converted my stock shifter to a cable. mine is also a lock up converter 4.1 gear

I believe that was 1wildRT that came up with the notching.

To me, the down side of the 518 is the crappy 2.45 first gear ratio is a carryover from the 727. The 700R4/4L60E has a 3.06 first gear but second is a tall 1.62. That is a wide spread, sort of reminds me of the 833 OD 4 speed.

I thought the Mopar OD’s had low gear sets in them compared to old 727’s. ??

Unless there's been a price increase? I've done the SST GM 4L60 for just under $5K for the Mopar BBlk set up complete kit


Mike

And yet another option is to run a 2004R from Extreme Automatics with a lock up converter. I did have to cut the center loop out of my torsion bar cross member and reinforce it. Their Stage 3 trans will hold up to 1000 hp/850 ft lbs of torque. Uses a Reid bell housing to bolt up to small block, big block and Gen 3 Hemi's.

The gear ratio's are perfect with a 2.76 first and a .66 overdrive. With the lock-up on a 3800 rpm stall converter, its like having a 5th gear. Best functioning transmission I've ever driven. One wire for lock-up.

I painted mine black, and have never been asked if its a GM trans, Shhh.

2.45,1.45,1.0, .69 even with a 3.54 gear my car pulled great, 1.55 60ft, VERY mild 512. 4100lb pig

Agree.

Taking off in first or the first to second gap is not an issue unless you have a real dog like a slant six.

A 545rfe with a 5.7 is a party in first and second. Once that thing hits third, the party is over: 1.5, 1.6ish ratio 2nd gear to 1:1 third is a big jump.

Over $6 grand for it AND GM base tranny????? I can afford it but looking at it, is it feasible? If I pull the trigger for OD, I can't see having a GM anything on my car it has to be Ma Mopar. IMHO

My street car would Grenade a 4l60

$6k can buy me A LOT of gas..It would take me YEARS to recoup the investment . even at 5 or 6 miles per

Bearing in mind I plan to drive the snot out of the car locally. BUT,,,,,,,and/if I should decide to make a longer distance trip. I'll rent a truck and trailer for a few days

I never thought about costs versus return on fuel. Car will have a decent build 440. I haven't finalized the build options as I tend to always want to go overboard. But stock stroke and 0.30 over pistons. I have a completely done set of 452 iron heads with minor smoothing, no porting. And a set of used Edelbrock heads. Not sure which way to go there. Drivetrain is not numbers matching and I started to think about making it more modern with fuel injection, more gears in the transmission, and other changes. The idea is to do that versus buying a modern muscle car. I'd love a manual, but was leaning towards keeping it an auto.

Thanks for all the suggestions. Certainly some options to think about.