Overdrive 727?

I Was Wondering If Anyone Knows How To Get A 727 Trans To Have Overdrive? I Never Have Seen This But I Was Talking W/a Guy Who Swears He Had One, Only Problem Is He Doesnt Know How It Was Done. I Think He's Probably Full Of Shit But I Could Be Wrong. I Have Been Wrong Once Before I Think. Anyways If You Have Heard Of This Let Me Know.

 

Overdrive was added to the 727 and the numbers were changed, sometime in the mid 90's. I think it became the A518, but I could be confusing that with the updated 904.

 

I know the early 90's dodge pickups had a 3spd auto with an electric overdrive on the back not sure if it was a 727 or not

 

Tose Wont Fit A 68 318 Though Would They?

 

there are aftermarket companies that make bolt on overdrives, kinda like adding another mini transmission to your existing one, don't know much else about how reliable or ease of installation

 

Gear Vendors makes an external overdrive, but a A-500 or A-518 transmission could be an option- are you looking at a small block or a big block?

 

Take a look through this link.......

http://www.coperacingtrans.com/odunits.htm

 

If you use a late model Dodge truck overdrive they have an electric governor as well as electronically controlled o/d....the truck PCM controls it.I doubt you could use it easily.

 

yea, you could, it just takes 7 volts input current cant remember the amperage though. if you go this route make certain you understand that this transmission has problematic areas and to me really isnt suited for hotrodding. the look-a-like transmission behind the diesels is a little better but not much. avoid anything with a lock up converter too. mopar has run this same transmission as a spin-off from the old iron 727s for years. the later versions 46 re,rh, a508, a518, and so on are just a continuation of the same thing, but cheaper and full of more crap. the a508 is considered light duty at best and is behind v6's. any la style small block and v6 has the same bellhousing pattern. the magnums are the same as the la in that regards too. the diesels take an adaptor. the new hemis also share the same pattern.
the convertors for all the transmissions in those years are set up loose. the best thing to do is contact rich allison at a&a transmission.

 

Not sure the newer overdrive stuff is as problematic as you think? Lots of guys run them in pretty stout cars and trucks, a street rod shouldn't be problematic at all.
RE models are tougher to hook up, but the A500/A518 isn't too hard.
Here's a guy who does quite a bit of overdrive stuff... maybe drop him a line and ask if you are looking at the right applications...
http://www.smrtrans.com/

I've drag raced the lock-up converter small block trannies for years and years, never had any troubles whatsoever.
They were 904 based.

 

A guy here in Oz is selling the A518's on the moparmarket site and when I asked a few questions about them he sent me this link
www.transmissioncenter.net/dodge.htm
Don't know any more about them but I was interested cos of the 31% overdrive.
Does anyone know what they come in? It's a bit risky getting one over here cos no-one knows about them if you have a problem.

swifty

 

I used to be a mech in a Chrysler dealer and what Chitbox and Crazy Mopar Guy have said is spot on.

The OD was a bolt on Borg Warner unit if I remember right. The mains trans was basically a 727. Decent unit, but if there was ever a failure in these units, 90% of the time it was the OD unit. One of the main things with these was keeping the cool. We saw some sucess by adding coolers to them. Didn;t prevent all failures, but it helped. If you use one from the late 80's or early 90's they would work behind older small blocks, provided the balance was coorect for the engine in question.

 

I've got the a518 in my truck, I hate it, buts its held up for 252,000 miles. I wish I had the lockup converter, then I'd be happy with it.

 

Its A Small Block 318.

 

The gear vendor unit is a great unit, at can be engauged at any rpm and load and is stated to be good up to 1000 HP. The downside is that they are expensive, about $2300

Brick

 

I still don,t see how the electronic governor pressure transducer as well as the O/D and lockup solenoids would be controlled. On the trucks the PCM does the job. I believe the overdrive units are made by New Process.I rebuild these transmissions and know how badly they work if the pressure transducer voltage is incorrect.I see the transmissions shown in the link have the wiring harness connectors on them....

 

I'm pretty sure you get a stand-alone brain box that controls this.

 

That would explain it! Thanks.

 

The mopar computer simply controls when the voltage is applied to the OD. Therfore, it can actually be controlled manually in a number of ways. One of them is simply with a manual switch, turned on like you would a cruise control, and cancelled with a brake switch. Yes, this means you have to pay attention when you drive it... and I am purposely over simplifying it, there are other mor complicated ways as well but I think you can get the idea.

 

hey,i have a 727 out of a 1985 dodge with an american overdrive unit on the back for sale. i just drove this unit from phoenix to gainesville fl.the overdrive works great,the tranny has a few issues.i also have a strong 360 engine out of the same truck.
i bought this truck to swap in a diesel.
Randy

 

Street Rodder magazine actually did an article on these trannies several years ago, I'll find out what issue it was in for you.

I have had both the A500 and the A518 in vehicles, as long as they are taken PROPER care of, they are great trannies. Look up rebuild kits for them- all the internal parts are the same as the 904 and the 727, except the gaskets. I've never heard anybody say a 727 is a shitty trans.

 

I must be talking newer units because the shifts are definitely pcm controlled through an electronic governor. I,m refering to late 90,s units.

 

I believe '95 and later are computer controlled shifting

 

Yeah that must be it cause I rarely see a truck that old at the dealership! They get beat to shit up here and don,t last long....The Chrysler data base I have access to doesn,t have anything that old in it!

 

That explains things to me too, although I admit that my memory may be faulty on how to make these early units work without an SBEC. I left the dealerships and went in to engineering in 1990. Makes sense that they would have done this with some of the trouble we were seeing. I am also thinking that the early units had lockup convertors. Sounds like maybe the later ones didn't?

 

Do Some Older Trucks Have Od That You Could Find In A Junkyard? If So What Years?

 

I believe 87 Dakotas and fullsize trucks had O/D trannys.From then on I think they all had lockup torque convertors. If I remember correctly the overdrive tranny best for you would be one that has a three wire connector plug in near the shifter shaft OTHER than the neutral safety/backup switch.It would point straight up.One wire for power and one ground wire for each lockup and overdrive solenoid which is on the valve body. I have many Chrysler manuals stashed away if anyone needs wiring diagrams.

 

I Could Use A Diagram For This Man. I Need To Put A Picture To The Words So I Can Make Some Sence Of All This. On The 87 Dakota, Is It A Seperate Overdrive Unit That Bolts On The Trans. Like An Older O/d Unit From A Willy's Or A Jeepster?

 

The O/D bolts on to the back of the main body but it can,t be used on an older case.There is an apply piston on the rear of the main case to apply a clutch in the overdrive.You will have to get a complete unit or find an aftermarket add on.... I,ll post some pics soon as I can.

 

Here is a diagram for a 91 A518.Solenoids on the bottom right.Use ignition feed to the J2 14DB,you could use a vacuum operated or toggle switch for the lockup and possibly the same for the overdrive.The 2 wires will ground the solenoids through the switches allowing redirection of hydraulic pressure to apply the lock up or O/D.