727 Overdrive

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aacwilliams

aacwilliams

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I have a 727 with an overdrive that i want to put in my 68 Barracuda. The tail shaft is about ten inches longer than a regular 727. Will it fit in the trans tunnel? What is the best way to fab a new crossmember and moount?
 
aacwilliams said:
Whats a 581?
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He said 518, not 581. And it's the overdrive version of a 727 that your mis-naming as a 727 with overdrive. When they made it into a od trans. They no longer call it a 727. They call it a 518. Some manuals also call it a 46rh (early yrs) or 46re (later yrs).

Do a search for 518 installation or overdrive installation and you'll find numerous threads on this subject. In fact about once a week someone gets on here asking the same question as you. I don't know the answers but I know there are numerous threads on it.
 
Thanks for the info. The 581 thing was a mistake in typing. I am a new member, sorry about asking the same question that has been asked before.
 
aacwilliams said:
Thanks for the info. The 581 thing was a mistake in typing. I am a new member, sorry about asking the same question that has been asked before.
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No problem. I was just letting you know there are a lot of threads on it. Some even have pictures. Good luck finding your info.
 
I believe to fit the 518 you will need to do some surgery to the torsion bar crossmember where it runs over the transmission, fabricate a new crossmember and to some sheetmetal work to the tunnel also. There is also the issue of switching on the od and locking up the converter clutch...
 
Thanks for the information. Maybe a 727 is a better choice if the 518 involves that much cutting.
 
Considering the work involved and cost to rebuild a 518 I think it might be better to install a low 1st gear set in a 727 and run taller rearend gears. Cost of the low gear set isn't cheap but then again rebuilding a 518 isn't either and it would save you a bunch of work. Just my .02
 
From what my trans buddy told me a 518 will cost a small fortune to build and have live. Not many valve body choices for it neither. Could always put something else in it like a 4l80e.....but the purists will have some issues....

16.jpg
 
inkjunkie said:
I believe to fit the 518 you will need to do some surgery to the torsion bar crossmember where it runs over the transmission, fabricate a new crossmember and to some sheetmetal work to the tunnel also. There is also the issue of switching on the od and locking up the converter clutch...
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I really don't think that you really need to do ANY sheet metal work. Some guys use rectangular tubing where they need to do sheetmetal work, Hot Rod Magazine did an article on this in 2008...

http://www.hotrod.com/howto/43323_mopar_overdrive_transmission_swap/index.html

It may be a GTX, but same principle. It looks like they welded in either 1/8 or 3/16 flat stock.
 
My trans guy--who is in to mopars--says mopar doesn't make a good o.d. trans. For everything involved you do seem better off with a gm o.d. trans

Either that or just grin and bear those 4000+ rpms runs on the freeways, lol.

Mopar sold many cars with 3.55 gears back in the 70+ mph days. Hear stories from my father friends how traffic used to go 80 to 90 mph back in the late 60's early 70's. Nobody had o.d trans either. This was way back around 1980 I heard about it so it wasn't like they were old back then and foggy on their memories.

Yeah people also brought new cars before the car was 5 years old!
 
518 (46rh)..spend about 5 hundred including converter in my 94 ram 2500 with 300k.
 
fishy68 said:
Considering the work involved and cost to rebuild a 518 I think it might be better to install a low 1st gear set in a 727 and run taller rearend gears. Cost of the low gear set isn't cheap but then again rebuilding a 518 isn't either and it would save you a bunch of work. Just my .02
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the guy that i know that put a 518 in did do some sheet metal cutting. but after the fact he says he really didn't need to.. its all in how you deal with the cross member...
 
dodge freak said:
My trans guy--who is in to mopars--says mopar doesn't make a good o.d. trans. For everything involved you do seem better off with a gm o.d. trans

Either that or just grin and bear those 4000+ rpms runs on the freeways, lol.
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from what i have read the 518 is really just a 727 with a OD unit bolted to it. nothing wrong with a 727 is there? the OD units had some oiling issues from what i have read. there are easy modifications that can be done to make they hole up.. i know i had a link with the mods need but damned if i can find it right now...

Mopar sold many cars with 3.55 gears back in the 70+ mph days. Hear stories from my father friends how traffic used to go 80 to 90 mph back in the late 60's early 70's. Nobody had o.d trans either. This was way back around 1980 I heard about it so it wasn't like they were old back then and foggy on their memories.

Yeah people also brought new cars before the car was 5 years old!
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gas was only 50 cents a gallon back then too...lol. they just didn't know any better back then. OD will give ys the best of both worlds. great performance around town and on the track and great cruising RPM and better MPG.. if you really want to drive and cruise your car its a great option. i know cruising my dart with a 28" tire and 3.91 or 3.55 gears sucked. yea around town it was a lot of fun but crank it up to 85 on the highway for an hour and it was horrible. the 2.94 gear in it now is a lot better but still not enough for me.. :) i really want a OD unit in my car..
 
ramenth said:
http://www.dippy.org/forum2/index.php/topic,231.0.html

I'm throwing this up as someone pointed out the wiring issues. Look at the bottom of the article and you'll see that on one conversion oil pressure switches were used to control the OD and lock up, essentially letting the trans itself select when for both.
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here ya go.. you can buy the switches as a kit.. http://www.redrider.us/518_parts.htm


PATC 727 to 518 Conversion Kit​
#727518. With these four parts you can convert your 727 transmission to a 518 overdrive transmission with locking torque converter. [FONT=Arial, Helvetica, sans-serif]Lets say you drive an average of 400 highway miles per week, at that rate you could save as much as $1000.00 per year on gas, not to mention the 31% reduction in RPM. Your new 518 will have automatic shifts into overdrive and lock-up, no toggle switch needed. Now with adjustable vacuum switch. The instructions are at the bottom of this page. [/FONT][FONT=Arial, Helvetica, sans-serif](11-25-06. I just saw this kit on the Internet by the copy cat competition for $1654.00.) [/FONT][FONT=Arial, Helvetica, sans-serif]Cost $85.00 Qty 12345
Overdrive 44 MPH48 MPH
Converter Lock-Up 50 MPH52 MPH[/FONT]
IMG_0750.JPG
 
inkjunkie said:
From what my trans buddy told me a 518 will cost a small fortune to build and have live. Not many valve body choices for it neither. Could always put something else in it like a 4l80e.....but the purists will have some issues....
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4l80e is double the weight and uses more hp to turn, the 904 soaks up 26 hp and the 727 soaks up 44.

The 518 needs the shaft drilled to increase oil to the od...
OR
don't race in OD or pull stuff and it'll be fine....
OR
Get a GV and have 6 spds to choose from....


Now putting the 518 in place of the 727 you need to cut the trans cross member and lower the mount.. i do not remember doing anything else.

Remember never leave the trans in park for long periods of idling...

.
 
Get a GV and have 6 spds to choose from....
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GV doesn't have as good of OD ratio. wish they would give it more.... does anyone really split gears with it? the guys i know that run them say its too hard to split gears at the track with them...
 
727 with a gear vendor, how do you run a loose convertor behind an 850 hp fuel injected Hemi? Call Len at Ultimate convertor and ask him about the Hemi Cuda in Vegas with the 727/GV he has been working with. Twice the weight of of a 727? is that with our with out the gear vendor?
 
abodyjoe said:
gas was only 50 cents a gallon back then too...lol. ..
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Nope, it was 16-17 cents a gallon. I recall when gas top 25 cents a gallon, was big news. Yeah then the party stopped in 1973 with the oil shortage. Forget high prices, many people were limited to 8 gallons every other day. Or you had to sit in long lines, maybe an hour long--even push your car up to the gas pumps if you had no more gas.

In a way we have it very very good today, lol. as you as you are rich:sign10:
 
What is really needed is an aftermarket auto trans with o.d.

The manual trans guys have it made. lots of 4 5 speed trans--lots of hp clutches but like for autos there isn't any aftermarket trans.

Maybe the auto guys are too hung up on using a trans that has the same name on it as their has.

Wish TCI or somebody would make from the ground up a hp auto trans with different bell housings to fit most v8 motors. And sell the darn thing for $1,000, lol Be cheaper to buy a torque converter too.
 
dodge freak said:
Maybe the auto guys are too hung up on using a trans that has the same name on it as their has.
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And that is pretty much the truth. These are probably the seem people that say you can not get decent street matters with a 10 second (or faster) car. The old school train of thought, there is to many compromises that must be made to run a 10 second (or faster) car on the street comes to mind....
 
abodyjoe said:
GV doesn't have as good of OD ratio. wish they would give it more.... does anyone really split gears with it? the guys i know that run them say its too hard to split gears at the track with them...
Click to expand...

With a manual it's a little tricky, with the auto it's just a push of the button when in 2nd..

I have 3 GV's owned all of them for well over 10 years, the best product i think i ever used.... was so good i started selling them and installing them..

The manual trans in racing apps, you gotta pull the switch as the switch is engaged you then quickly depress the clutch just enough to slip it and back off the pedal....
You can practice this going thru the gears on the street...
The auto can deal with engaging under power do to the tc absorbing some of the shock..
With the stick it feels like you crashed a gear, and it is the only thing that'll make issues for the GV...

Once you get the hang of it you/ll never hear the shift, in my truck you'll think i got a very quick auto, when towing i can go thru 7 speeds and you'll never notice it was a stick.

However keep in mind there are a lot of steering wheel operators out there, not many drivers

.
 
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