RPM's with gear change
06-29-2009, 04:38 AM
#1
Thread Starter
Join Date: Jun 2009
Location: Indiana
Posts: 2
RPM's with gear change
I have a 2005 GT with a 3.55 gear. I want to change the gear to a 4.10 or possibly a 3.73 My GT now runs 65 MPH at 2000 RPM's in 5th gear. What would the RPM's be at 65MPH with 4.10 or 3.73 gear. Question #2 would it even be worth changing to the 3.73 gear, would it be enough improvement to justify the expense.
06-29-2009, 12:15 PM
#2
6th Gear Member
Going from the 3.55's to 3.73's won't be too noticeable. I personally wouldn't bother.
I have a spreadsheet for the RPM's but it's on my other PC which isn't available at the moment. But you'd be turning about 200-300 more RPM's, if that if I recall, with the higher gears. Hopefully someone else can send you the spreadsheet.
I have a spreadsheet for the RPM's but it's on my other PC which isn't available at the moment. But you'd be turning about 200-300 more RPM's, if that if I recall, with the higher gears. Hopefully someone else can send you the spreadsheet.
06-29-2009, 12:59 PM
#3
3rd Gear Member
Join Date: Jan 2008
Location:
Posts: 530
I agree if you are going to spend the money, go to 4.10s or don't bother. At 65mph, you will be running close to 2500 rpm with 4.10s.
Keep in mind that overall wheel/tire diameter will change your ratio as well. For instance, my drag radials are 1.5" shorter than my stock tires. So at the track, my final drive ratio is 4.34.
Keep in mind that overall wheel/tire diameter will change your ratio as well. For instance, my drag radials are 1.5" shorter than my stock tires. So at the track, my final drive ratio is 4.34.
06-29-2009, 01:23 PM
#5
6th Gear Member
Join Date: Feb 2007
Location: state of confusion
Posts: 7,635
3.73's will barely put the revs above 2100 rpm at 60. RPM-wise there isn't any street-driving basis for changing from 3.55's to 3.73's. In competition, you might choose one or the other based on being able to drive in a very specific range of speeds with just barely not having to upshift.
Is your car manual or automatic?
Norm
Is your car manual or automatic?
Norm
06-30-2009, 12:18 PM
#7
3rd Gear Member
Join Date: Jan 2008
Location:
Posts: 530
I don't know what direction you are taking the car, but wish I had 3.55s or 3.73s. During auto x, I run out of 2nd gear when most people have room to spare, that makes driving more difficult. For road racing, 5th gear might actually get use, which has an economy ratio = slow. Moreover, the car is very twitchy with 4.10s when racing around curves, so while you have more torque, putting it to good use requires more skill (pretending there is an egg under the accelerator pedal)
But if you are just ripping around your neighbour hood and drag racing like 99.998% of Mustangs, go for the 4.10s.
But if you are just ripping around your neighbour hood and drag racing like 99.998% of Mustangs, go for the 4.10s.
07-02-2009, 01:32 AM
#9
2nd Gear Member
Join Date: Nov 2008
Location: texas
Posts: 199
It all depends on your wheel/tire height. I run 4.30 gears with an overall tire height of 28.68". I think thats an inch over stock. The gear ratio is effectively reduced to 4.10s at the wheels. Anyways, it runs 1800 rpms at 55mph and 2250 rpms at 65 mph. Just putting the info out there in case it helps someone.
