66 Mustang C4 Gearbox Problem

Lasse · Jun 8, 2012

Hi Mustang fans.

I would like to ask your advice about a gearbox problem.

I am considering buying a nice 66 Mustang with the so called “green dot” C4 transmission. It runs fine except for one thing. When driving at normal road speed, it sounds like the engine rpm is much too high, and I have a feeling, that it’s running in second gear.

The strange thing is, that it feels like it shifts just fine during acceleration. It clearly shifts from first to second. At higher speed it feels like a fairly smooth, yet noticeable, shift from second to third. When I hit the gas at about 40-50 mph, it feels like it shifts down to second, again fairly smooth, and then it accelerates. In other words, everything seems fine.

I just can’t hear any change in the rpm, when it supposedly shifts between second and third. What could be wrong?

Can an automatic transmission behave like that: It feels as if it shifts between second and third, but it actually stays in second all the time?

Or is it perhaps a problem with the converter?

Other ideas?

Maybe you have experienced something similar. I would really appreciate your advice.

iskwezm · Jun 8, 2012

Something i found

One the dual range units, the designations were: P, R, N, a Big Dot, instead of D for Drive, a Small Green Dot for the 2nd range and 1 or L (low) for first gear. The kicker is that the middle, small green dot was for drive, meaning it would start in first and shift normally through out the gear ranges. The confusing part (unless you read the owners manual) was that the first Dot or the bigger dot, which is what we are used to as the ‘Drive’ position actually would allow the car to only take off in second gear.
Ford did this for a couple of legitimate reasons. When one is driving on a slippery surface such as snow or mud, starting off in second gear, or a higher range, makes it easier to get traction from the drive wheels to the ground. This was a cool and effective feature, which was exclusive to the early C-4 Cruiseomatic only, but was dropped by 1966 for obvious reasons, as I said, people were often confused on how to properly drive the car.

woodsnake · Jun 8, 2012

Not to mention, that if you are not used to driving a car from "back in the day" a V8, it will sound and actually be turning higher RPM's. As I recall, a 3.0 geared v8 with 14 inch tires will be around 2800 at 65 mph. But I am no where near my car, so I am going by memory here...Have you got a tachometer in the car, or just going by ear?

Lasse · Jun 9, 2012

No, there is no tachometer, so i'm going by ear. Furthermore, the car has flowmaster exhausts, which makes it extra noisy. Still, i'm pretty sure, the rpm is to high. This will be my first american car, but I've driven a few of them. And the other classic american cars I've tried, seemed to go at lower rpm, when travelling at normal road speed.

I know about the big, and the small dot. I was driving in the small green dot, as I am supposed to. I also know, that a lot of people got it wrong, which makes me worry about, whether the gearbox has been damaged.

horse sence · Jun 9, 2012

i would check the rear gears and see just what gear ratio you have
3.50 would be way to low 3.00 would be good for an automatic.
is the transmition actualy shifting 1-2-3 from take off ? is the passing gear
lever hainging up or adjusted wrong

Lasse · Jun 10, 2012

It seems to shift 1-2-3 from take off. I don't think there's af problem with the passing gear lever, as it also seems to shift from 3 to 2, when i hit the gas. I just can't hear any change in rpm.

I will check the rear gears. Maybe it's a wrong rear gear ratio, combined with the noise from the flowmasters, that tricks me. I was told by someone, that I should take it on the highway and see if it goes more than 75 mph - because then it's definitely in third. I think I'll try that too.

Thank you all for your advice.

horse sence · Jun 10, 2012

y

Lasse said:
It seems to shift 1-2-3 from take off. I don't think there's af problem with the passing gear lever, as it also seems to shift from 3 to 2, when i hit the gas. I just can't hear any change in rpm.

I will check the rear gears. Maybe it's a wrong rear gear ratio, combined with the noise from the flowmasters, that tricks me. I was told by someone, that I should take it on the highway and see if it goes more than 75 mph - because then it's definitely in third. I think I'll try that too.

Thank you all for your advice.

you may want to hook up a tach just to see what range you are running in, the loud exhaust may be misleading.

66 Mustang C4 Gearbox Problem

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iskwezm

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