2003 & 2004 GT's And Non-Factory Rear Gears...

[92blustang]

For those here who have either an 03 or 04 GT with a 5 speed manual, I would really appreciate your help with something.

I am in the process of choosing a rear gear upgrade and am interested in discovering an actual RPM/MPH observations of owners of ONLY 03-04 GT's 5-speeds who have upgraded to either 3.73, 3.90, or 4.10 gears.

I have searched the topic and see only general RPM/MPH figures for earlier models having a different 5th gear ratio and have yet to come across the ACTUAL RPM/MPH figures for SPECIFICALLY 03-04 GTs.

So, if anyone here has an 03-04 GT, can you please tell me precisely what RPM you are turning at highway speeds? I am interested in knowing what RPM the 03-04 GTs with 5 speed manuals are turning while at 60, 65, and 70 mph with either 3.73, 3.90, or 4.10 gears.

THANK YOU!!!!!!!!

 

[Sonic04GT]

Here ya go. Found these from a recent road trip. Doesn't get more exact than that. Only around 75mph though. With ~2,300 RPMs @ 75mph, I don't think the other speeds really matter

 

[92blustang]

I haven't been on the highway but let me see if I can dig up some pics that may include the instrument cluster from my recent road trip.

I have 3.73s. I think I'm around 2800rpms at about 80mph.

THANKS!! By the way, that is a BEAUTIFUL color blue that your GT is. Absolutely BEAUTIFUL color.

 

[sneaky98gt]

I don't have an 03-04 Mustang with the 5-speed, but I do have a calculator built in Excel that uses the rear gear ratio, transmission gear ratio, tire height, and speed to determine the RPM. It is very accurate on my car (roughly +/- 20 rpm).

Assuming your tires are 25.66 inches tall (stock tire height), and your 5th gear ratio is .62:1 (what it is supposed to be from Ford), your RPM will be:

3.73s
60 mph: 1818 rpm
65 mph: 1969 rpm
70 mph: 2121 rpm

3.90s
60 mph: 1900 rpm
65 mph: 2059 rpm
70 mph: 2217 rpm

4.10s
60 mph: 1998 rpm
65 mph: 2164 rpm
70 mph: 2331 rpm

Hope this helps.

 

[sneaky98gt]

Yup, according to my calculator, you should be at 2272 rpm at 75 mph (with 3.73s, stock tire height, and .62 OD ratio), and you are at 2270. I'd call that pretty dang accurate.

 

[usaf_branham]

with 4.10s i was taching a little over 2500 in 5th, gas mileage dropped from around 28mpg to around 23mpg highway. (at 75 mph)

with 3.73's i am taching the same as above.

i miss my 4.10's... the car was much more fun to drive, but the 3.73's are more practical with my setup.

 

[92blustang]

WOW!!!!!! Thanks a lot everyone, these replies are a HUGE help to me!!

THANK YOU ALL!!!!!!!!!!!!

 

[Sonic04GT]

Yup, according to my calculator, you should be at 2272 rpm at 75 mph (with 3.73s, stock tire height, and .62 OD ratio), and you are at 2270. I'd call that pretty dang accurate.

Well done sir That is with 315/30/18 tires. Not sure of their height.

 

[Deleted member 38176]

/feels left out