Overdrive for C4

mhjo · Nov 30, 2009

I 3:00 rear and C4 wich gives annoying high rpm when I go fast on highways.

I am wondering if anyone makes overdrive option for C4?

D.Hearne · Nov 30, 2009

"Gearvendor" overdrive. Ain't cheap though at about $2400. Better to swap to an AOD.

mhjo · Nov 30, 2009

AOD's are impossible to find in my country (Norway) - unless someone can send me one....

D.Hearne · Nov 30, 2009

3.00's on the highway with a C-4 isn't that bad. I drive my 77 Comet regularly at 75 with 3.50's with 295/50/15's on the rear.

D.Hearne · Nov 30, 2009

Shipping an AOD to Norway would be expensive too, I would think.

2+2GT · Nov 30, 2009

I'm curious to know what you mean by "fast". The 3.00:1 was second only to the 2.78:1 for economy. I usually hear the rpm complaint about the 4.11:1.

What year is your Mustang?

What is the shift pattern on the shifter?

mhjo · Nov 30, 2009

Hi 2x2!

I like to go 70-80 mph, but the engines rpm is high (and drinks fuel..)

The C4 was rebuild by former owner (who owned the car 3 years after me selling it to him). The car is '65. Don't know what you mean by shift pattern, but if it is the markings on the lever you mean, it has one small spot and one ring symol on it (starting in 1. and 2.)

2+2GT · Nov 30, 2009

mhjo said:
Hi 2x2!

I like to go 70-80 mph, but the engines rpm is high (and drinks fuel..)

The C4 was rebuild by former owner (who owned the car 3 years after me selling it to him). The car is '65. Don't know what you mean by shift pattern, but if it is the markings on the lever you mean, it has one small spot and one ring symol on it (starting in 1. and 2.)

Excellent! You have the "Green Dot" Cruise-O-Matic. Assuming you have the correct trans to go with it, the shift pattern is:

P
R
N
•
O
L

The "•" is a special position for driving in rain or snow, and eliminates first gear. The "O" is the normal driving position. "L" is for downshifting, such as into a turn.

mhjo · Nov 30, 2009

Yes, But I need an overdrive! What and where to go?

woodsnake · Nov 30, 2009

Gear Vendors under/overdrive auxiliary transmissions Hot Rods, Ford 3-Speed Automatic Muscle Car/Street Rod/Restoration.

mhjo · Nov 30, 2009

Hmmm.. nice stuff, but pretty stiff price there. With my 3:00 it should shift into a relaxing 2.34...

Any other alternatives?

rbohm · Nov 30, 2009

what do you consider too high an rpm? at 75 mph with 25.6" tall tires, which is what came stock on the early stangs, and a 3.00 gear your rpms should be about 2950.

mhjo · Nov 30, 2009

Sure, but I would like it to go under 2000....

2+2GT · Nov 30, 2009

mhjo said:
Yes, But I need an overdrive! What and where to go?

I just wanted to make sure you use the correct position. You'd be amazed how many people here drive around in second gear all the time.

In your position, I'd change to a T5 5-speed manual trans. It'll give you the overdrive you want, at less cost than adapting some oddball overdrive to your C4.

RGS0907 · Nov 30, 2009

mhjo said:
Sure, but I would like it to go under 2000....

You could replace the 3:00 rear with a lower (numberically) ring & pinion and go to a larger diameter wheel and tire for less than the cost of an AOD or Gear Vendors setup. You would also need to change your speedo gear otherwise the speedometer will read faster than you are actually going.

D.Hearne · Nov 30, 2009

RGS0907 said:
You could replace the 3:00 rear with a lower (numberically) ring & pinion and go to a larger diameter wheel and tire for less than the cost of an AOD or Gear Vendors setup. You would also need to change your speedo gear otherwise the speedometer will read faster than you are actually going.

I was about to suggest the same thing. Going with a 2.79 & a 1.5" taller tire/wheel (215/70/14 to 225/70/15)would reduce the rpms at highway speeds by 300 rpms. Just the gear change alone would lower it by 200 rpms. This would be the easiest, most cost effective way to reduce the revs at highway speeds.

woodsnake · Nov 30, 2009

Do you have a junk yard that specializes in American cars?
You might be able to find an AOD "locally", maybe?

mhjo · Dec 4, 2009

What is model number that I should look for ? Is an AOD direct fit?
(Yes, I know I have to shorten axle)

Here is one I found on ebay:
FORD AOD-AODE-4R70W

D.Hearne · Dec 4, 2009

mhjo said:
What is model number that I should look for ? Is an AOD direct fit?
(Yes, I know I have to shorten axle)

Here is one I found on ebay:
FORD AOD-AODE-4R70W

The AOD differs from the AODE and 4R70W in that it's mechanically controlled via a throttle valve cable. The later two are electronically controlled by the EFI ECM. The AOD will bolt up to your block, as will the other two, but I'm not sure about the fit with the transmission crossmember

woodsnake · Dec 5, 2009

There are a lot of posts about swapping to an AOD transmission, lots of good info.

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