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Recently purchased a very clean 72 Mach 1 and need to tame it's drinking problem a little; looking to make a cruiser with go power. It's coming with a C6 with a 4.11 in the rear end; and I'm looking to change them to a 4R70W trans with 3.50 gears. The engine is a 315C 4V and according to the rebulider pushing 380 horses. Sound off folks.....good choice or bad.

 

24.thumb.JPG.d6ad71a7097c81af678fd36d25bd8626.JPG

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I know very little, but you could keep the 4.11's with the 5 speed AOD and you will have the best of both worlds, I would think.

Steve

 

[button=http://www.7173mustangs.com/thread-1972-mach-1--1800]The Stable[/button]

 

25yvyp3.jpg

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That sounds like a perfect combination to me. I did a wide ratio AOD (which uses thev4R70W gears) in my '73 and put in a 3.89 rear end. My engine is 2v, but I have upgraded the intake manifold and carb to Edelbrock combination with dual exhaust. So I figure I have around 200hp.

 

I cam smoke the tires whenever I want from a stop, and get a great launch. And highway speeds are still good RPMs (high 2,000s) with 26.4" tires.

 

In hind sight, I would have been just as happy with 3.7 gears. With the amount of power you are looking at, 3.5 will be amazing with the 4r70w, and you will get really good mileage at freeway speeds.

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Drewxx72,

 

sm3570, Luke, CZ-75 have a valid point. According the 4R70W tech specs, the gear ratios are: 1st: 2.84 :1, 2nd: 1.55 :1, 3rd: 1.00 :1, 4th: 0.70 :1, Rev: 2.23 :1

According to the gear ratio calculator I found, 15 inch tires and 2200 RPM’s, you are running a speed of 55 MPH.

 

http://www.apexgarage.com/tech/gear_ratios.shtml

 

4R70W

176dtd.jpg

 

C6: 1st: 2.46 :1, 2nd: 1.46 :1, 3rd: 1.00 :1 Rev: 2.18 :1

t96wdx.jpg

 

According to the C6 gear ratio, running 52 MPH, you are turning 3000 RPM's.

 

Not a Bad combo setup here. Please take a look at the calculator and test the numbers.

 

mustang7173 :D

Thanks,

mustang7173 🇺🇸

"Courage is being scared to death but saddling up anyway" -- John Wayne

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Nice looking car! Welcome to the forum. I run a c6 and 3.5 gears also. My car has been that way for years and it too is thirsty. I just finished installing a gear vendor overdrive. I only have 12 miles on it so far so I can't give you too many details on it. If your c6 is running pretty good this might be an option for you. They are not cheap. It's a fairly straight forward install.

 

Price wise a 4r70w vs a gear vendors is going to be a push. A lot depends on how you source the transmission and how much of the wrenching you do yourself. You could do the 4r70w for half as much as the gv. The 4r70w has slightly lower first gear which helps off the line and a taller OD which would help on the freeway. (.7 for the 4r70w vs a gear vendor .78)

 

If I hadn't had the c6 already built I probably would have leaned more towards the 4r70w. One of the deciding factors for me was the passing gear. With the 3.50 and the OD on I can shift down into second on the transmission for a really nice passing gear that closely matches how the car originally was when I bought it with a 2.78 rear.

 

Starting over I would seriously consider a 5 or 6 speed manual.

'Mike'

73 Convertible - 351C/4V CC heads/4bolt/forged flat tops/comp 270/rhodes/mallory unilite/tri-power/hookers/glasspacks/c6/3.50 limited slip/Gear Vendors/Global West sub frames, strut rods and shelby style traction bars/ Rear sway bar/tilt steering (not original)

 

Pics of modifications included in: [button=http://www.7173mustangs.com/thread-1973-convertible--3335]My Garage[/button]

 

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73mach1,

 

yep- I made an error here. Here is the update with a 205/75-R15 = 27.106 in.

 

4R70W: Gear ratios are: 1st: 2.84 :1, 2nd: 1.55 :1, 3rd: 1.00 :1, 4th: 0.70 :1, Rev: 2.23 :1

 

2wdr6s5.jpg

 

C6: 1st: 2.46 :1, 2nd: 1.46 :1, 3rd: 1.00 :1 Rev: 2.18 :1

 

2cyp3qr.jpg

 

 

73mach1 -Thanks you for pointing my error out.

 

mustang7173 :D

Thanks,

mustang7173 🇺🇸

"Courage is being scared to death but saddling up anyway" -- John Wayne

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I couldn't be happier with the wide ratio AOD and 3.89 gears. Even with the neutered '73 motor, I can smoke teh tires, yet still get reasonable RPMs on the highway.

 

If you're going to have 27" tires, I would recommend 3.7 rear versus 3.5.

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If you're thinking of keeping the slushbox, the only feasible overdrive units are the AOD and AOD-E/4R70W. Keep in mind that an issue with the earlier controller-less AODs is that a) they are considerably weaker in torque output and b) they can burn up very quickly with incorrect TV linkage adjustment. A stock late model 4R70W is good for 500 hp, but requires an electronic controller; either a Baumann standalone unit or an EEC-V computer with the integral controller is required. Shift points are also adjustable with the 4R70W.

 

Personally, I'm going with the 4R70W since I just converted my engine to EEC-V and the computer has the controller.

1971 Mustang fastback: 10.3:1 C90E 408W hydroller - CDAN4 EEC-V w/EDIS8, girdled, lowered and caged

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4R70W with a Baumann is the way to go. I went AOD with mine, but mostly because a pal literally GAVE me the one from his '89 5.0 GT. If the AOD ever gives up, I'll replace it with a 4R70W & Baumann.

Eric

mach1sig2.gif

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I don't mean to slander the AOD, I was just trying to objectively expose the nuances with each unit. The AOD is the predecessor to the AOD-E/4R70W, but it doesn't mean it can't be built into handling serious power. I think it does take a bit more money, though. The possibility of using an AOD-E/4R70W wasn't even really possible until more recently, in any case.

1971 Mustang fastback: 10.3:1 C90E 408W hydroller - CDAN4 EEC-V w/EDIS8, girdled, lowered and caged

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No worries, Bro! I was just trying to say that I would've gone with the 4R70W if I hadn't been provided with an AOD for literally no cost - kinda hard to beat that price (OK - so I had to pay the guy's stall fees... all $32 of 'em). rofl

Eric

mach1sig2.gif

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73mach1,

 

yep- I made an error here. Here is the update with a 205/75-R15 = 27.106 in.

 

4R70W: Gear ratios are: 1st: 2.84 :1, 2nd: 1.55 :1, 3rd: 1.00 :1, 4th: 0.70 :1, Rev: 2.23 :1

 

2wdr6s5.jpg

 

C6: 1st: 2.46 :1, 2nd: 1.46 :1, 3rd: 1.00 :1 Rev: 2.18 :1

 

2cyp3qr.jpg

 

 

73mach1 -Thanks you for pointing my error out.

 

mustang7173 :D

No problem,wasn't trying to be a smartass just didn't want your numbers to be ascue.

Jay

73 mach1

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Jay,

 

None taken! I am glad you pointed it out. I do not want to give out bad information here.

 

 

David

mustang7173

Thanks,

mustang7173 🇺🇸

"Courage is being scared to death but saddling up anyway" -- John Wayne

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I'd go with keeping the 4:11s and getting a wide ratio 5 speed or even a 6 depending on your pocket. You can dig a trench in first and still have gear to haul down the freeway. Its like a mustang indy car, badass.

 

Nothing like grabbing gears!

If you don't have time to do it right the first time, you sure as Hell don't have time to do it right the second time.

 

Dutch uncle

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