4 speed automatic?

[duckbuster]

Does Mopar have a 4 speed auto that will hook up a mid 70's or 80's 318 small block. I have read this on some websites but nothing is clear about any necessary modifications. I know there 4 speed auto trans in some 1998 and newer cars and trucks but are they computer controlled?

 

[rumblefish360]

I'm not the clearest on the exact years of this stuff, but the early 4 spd trannys are regular 3 speed 904's and 727's with a added on O.D. unit at the tail section. The 727 is called a 518. I keep forgetting what the 904 is called when it is an O.D. unit. But that one will fit easiest with just a BFH (Big Freakin Hammer) to dent the floor pan for fitment.

You'll need to shorten your drivesgaft and fab up a mount. The early ones are not computer controled. Theres a button you wire up to click into and out of O.D or when you decel under 15 mph I think it is , it comes out of O.D. into normal 3rd gear.

The O.D. ratio is .69. Your new ratio will work out like this. 4.10 X .69 = 282.9

 

[duckbuster]

thanks rumblefish360.

 

[dgc333]

The computer controller tranny started in 96/97 time frame. The A904 version is an A500 then it latter was renamed 42RH but its the same tranny. The 727 is an A518 then latter a 46RH. The electronic ones are 42RE/44RE and 46RE.

Both the OD and the lock-up torque converter have solenoids so two contacts need to be made. There was just a very detail thread over on moparchat.com or moparts.com that talked abut using GM pressure switches tied into one of the pressure ports to activate and deactivate the OD and lock-up. And I am sure I saw in a street rod article that there is a module you can purcahse that goes in line with the speedo cable to do it too.

If you are planning on putting the tranny in an A-body then with either tranny you are going to have to cut the floor open cut the trosion bar cross member widen the area and fill it back in with either an A500 or A518.

A buddy of mine has an A518 behind a 340 6-pak motor in his 67 Barracuda and it works very well. The floor surgury is not noticable from inside the car and a stock floor console still fits.

 

[rumblefish360]

Thanks DGC. Why I couldn't remember the "500" number is beyond me.

 

[67valiant]

im pretty sure that you can get the over drive transmissions out or some older dodge rams and i think maybe ram vans, that is what mine was out of, i had the over drive 904 in my car and it was out of a ram

 

[superdart]

Actually, cutting the floor itself isn't necessary, but the crossmember will definately need to be cut down.

The trick with the OD is to use two pressure switches, one for OD, one for TC lockup. Then you have a vacum switch that cuts the ground to both of those circuits to push the car into drive and then passing gear during hard acceleration.

I have a link on the house PC that shows how to wire it in. I'll post it when I get home. PM me your email addy and I can send you the files and pics from when I did mine.