Ok, the question has been, did they change the 5th gear O.D. ratio on the 5-speed manual for '07??

I had mine at 60 mph today in 5th and the tach is dead-on at 1,750 rpms. How does that compare to those of you that have an '05 or '06 with the manual trans? I have the optional 18" tires, so let's compare apples to apples.

If anyone gets their '07 5-speed manual with the 3.31, please post your 60mph rpms.

 

I ran this through on of the auto calculators

http://www.csgnetwork.com/multirpmcalc.html

and it looks like 5th i still .675

 

With the 18" tires & .68 OD, I calculate 1787 RPM @ 60 MPH.
Looks like you have .68 OD

Now we need someone with an 05 or 06 to do the same.
05s and 06s are supposed to have 0.62 OD.
If the OD is .62, @ 60 MPH you should have 1630 RPM (either 17" or 18" tires).

 

I would expect the RPM's to drop slightly as the car breaks-in.

 

incomingRPG,

Why would you expect the rpm to drop as it is broken in on a manual tranny car???? The only reason I could see for that is if his clutch is slipping right now...

 

i will be sure to list my speeds when i get mne in, should be within the month

 

I would think that as the engine breaks in, it will produce more horsepower and torque at a given RPM. During this time I would also think that "friction throughout the drivetrain" would be reduced. Thus, the required RPM's to move the car forward at a specific speed would be reduced. Given the tight tolerances in today's engine building and manufacturing, it might not be noticeable on the tachometer, but I'd be curious to see the results after several thousand miles.

 

IncomingRPG, you don't understand how drivetrans work.

The tire diameter is fixed, the rear end gear ratio is fixed and the transmission ratios are fixed. The only way to change RPM at a given speed is to change one of those 3 items. If anything RPMs at a given speed will increase very slightly as miles are put on the car because rubber wears off the tires decreasing their diameter, but this is a small effect.

 

I don't claim to be an expert on understanding drivetrains, but can you explain to me why as a car is broken in, it gets better gas mileage. I would think that it is due to less "friction throughout the drivetrain" To overcome this friction, I would think that the engine would have to work harder, use more fuel and run at a higher RPM in order to do so.

 

If you pedal bicycle up a hill every day for a month. It will be easier towards the end of the month because you are stronger.
The Bicycle will still be turning at the same RPM for your given input. It just feels easier (better gas mileage).

 

Ok, I have an '06 manual, at 65MPH, I was going a hair under 2000 RPM...if I have the calculator figured out right, that's a .62 OD

 

You are supposed to calculate at 60 MPH, not 65...

 

I calculate 1941 RPM for .68 OD @ 65 MPH.
.62 OD would give only 1770 RPM @ 65 MPH

It's starting to sound like the T3650 OD ratio has been .68 all along, just the Ford literature has been corrected.

Anyone else with an 05 or 06 Manual care to check their RPMs at 60 or 65 MPH?

 

Is there a feature on the '05+ that shows RPMs digitally? This is a nice feature I have used a couple of times. Might help dial in a more approximate rpm to determine 5th gear ratio if its available on '05+. Again, not sure if it's available on the '05+.

HEC Instrument Cluster Diagnostics

http://mustangworld.com/ourpics/fcar/dtcodes.htm

Much more accurate that trying to watch the needle. Plus other nice features as well.

 

Ok, time to resurrect this one. For those of you with an '07 with a manual and the 3.31 axle with the 18" wheels, what's your rpms at 60? My 3.55 is 1,750 at 60 and 2,000 at 70.

 

i will check tommorow. i think i was actually close to 1500 at 60, but i will looktommorow and post later

 

i think its about that with my manual 05 GT

 

well after finally remembering to look. I believe the tach at 60 in my GT w/ 3.31's is right about 1500. maybe a hair less. i will try to pay more attention on the way home.

in other news my car has just over 500 miles on it, and i am averaging 21.3 mpg. even with the air on and all during break in!!

 

I agree with V10. .68 all along...

A manual tranny (T-3650), factory tires, 3.55 gears, here are your speeds at 1800 RPM:

1800: 12(1), 21(2), 31(3), 41(4), 60(5 with .68)..........66(5 with .62)

To make it easier to check your speed when you're supposed to be paying attention to the road, 2000 rpm with .68 will be 67mph whereas 2000 rpm with .62 would be 74. V10, would you back me up on this, sir? So the question is, are you going under 70 or over 70 at 2000 rpm? I believe everyone here will be chugging along at 67mph, regardless of 05, 06, or 07.

Say, is it Grabber Orange in here or is it just me?

 

Heck, while I'm at it, here are the mph's for T-3650 with 3.31's:

1800: 13(1) 22(2) 33(3) 44(4) 65(5 with .68) and... 71(5 IF you had .62)

After all y'all go back and check real close, you'll find we're all running .68 overdrive for our 5th gear. If I'm wrong, please feel free to update the thread...