Owners Of 2003 & 2004 With Either 3.73, 3.90, Or 4.10 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!!!!!!!!

 

[trinity_gt]

You can make that determination yourself if you know your current rear axle ratio. Let's say it's 3.27:1. A set of 3.73:1 gears will raise engine RPM by 1.14x. So if you turn 1800RPM now at a given speed then with 3.73s you'd turn 1800*1.14 or ~2053RPM.

In general:

RPM_n = RPM_o * Gear_n/Gear_o

where RPM_n is the "new" RPM with new gear ratio Gear_n RPM_o is the RPM you turned with the old gear Gear_o. For example:

RPM_n = 1800 * 3.73/3.27 = 2053.

Go out and measure your own 60, 65 and 70MPH RPM readings and plug the numbers into the forumla to see what you'd turn with whatever gearset you're interested in.

 

[stang74]

02 GT 5 speed with 4.10 and 315/35/17 rear tires....at 75mph Rpm is at 2500 dead on......

 

[92blustang]

02 GT 5 speed with 4.10 and 315/35/17 rear tires....at 75mph Rpm is at 2500 dead on......

Thanks, but you have a 2002, correct? There is a specific reason as to why I said "2003 & 2004" in my title and multiple times in my post. The RPMS on a 2002 do absolutely zero for me due to a different 5th gear ratio in the tranny.

 

[92blustang]

You can make that determination yourself if you know your current rear axle ratio. Let's say it's 3.27:1. A set of 3.73:1 gears will raise engine RPM by 1.14x. So if you turn 1800RPM now at a given speed then with 3.73s you'd turn 1800*1.14 or ~2053RPM.

In general:

RPM_n = RPM_o * Gear_n/Gear_o

where RPM_n is the "new" RPM with new gear ratio Gear_n RPM_o is the RPM you turned with the old gear Gear_o. For example:

RPM_n = 1800 * 3.73/3.27 = 2053.

Go out and measure your own 60, 65 and 70MPH RPM readings and plug the numbers into the forumla to see what you'd turn with whatever gearset you're interested in.

THANKS, trinity_gt, your post was very helpful!!

 

[trinity_gt]

Out of curiosity, what makes you think 03-04 MY GT TR-3650s had a different 5th gear than 02 MYs?

I've read that 03-04 Mach 1s had a taller 5th but all GTs were the same AFAIK...

 

[Jhunter]

There is a difference in the automatics for sure. They changed to the 75 from the 70 in 2003. Can't remember which but the over drive gear in one is .62 and the other is .67. I would suppose the high gear changed in the manuals as well.