Ford Mustang Forum banner

1 - 19 of 19 Posts

·
Registered
Joined
·
151 Posts
Discussion Starter · #1 ·
Looking to change gears to 4.10 in an o5 gt vert:

How much will I lose in top speed? For instance If the car goes to 143 with the speed limiter will the car only go 120 now?

How much will I lose in fuel economy. For instance if I'm averaging around 16-20 mpg now will I now get less than 16. I drive highway alot with a heavy foot 80-90 mph.

What is the average cost of getting the job done? I live in MA and called 2 shops, they said around $500 but I'll have to fix the speedometer problem. I guess I'll have to tweak the XCAL 2 programs to account for the 4.10 gears? Is this done through the SCT Xtreme Tune program?

I hear that if the job is done incorrectly, you can get a whining noise upon deceleration which can be fixed with shims??

I appreciate your help and thanks in advance........
 

·
Registered
Joined
·
886 Posts
not that simple, i'm afraid

well, actual top speed to the mph is probably impossible to tell. Not all GTs off the same production line will have EXACTLY the same top speed to start with. Then, figure in road surface and conditions, and it varies mile to mile. all comparison is purely theoretical and subject to too many variables to be at all useful. bottom line: it's a little lower. Do you need to go 147 instead of 132?:D

As for gas useage, it will be theoretically equal to the percentage increase in RPMs at a given speed. This, in turn, is a direct mathematical relation to the change in gearing. works like this:
(4.10-3.55)/3.55 = % of gearing increase = % increase in rpms for a given mph. It also more or less = the % increase in fuel consumption. "More or less" because effective load on the engine will differ because of the gearing change. Also, throttle mapping across the RPM spectrum differs, so fuel delivery is slightly different. If you reflash a custom tune to account for the gears, all this goes right out the window. All of this is null and void unless you drive PRECISELY the same way. I'd bet a big part of the declining mileage you will experience is the sudden fondness of the gas pedal for the floor board.:hihi: :hihi:

having said all that, if you go from 3.55 to 4.10, and were getting 17.5 mpg, you will then get 14.8 mpg. In a mathmatically perfect, theoretical world.:shigrin

bottom line: mileage is worse. Do the gears and enjoy the heck out of it.
 

·
Registered
Joined
·
151 Posts
Discussion Starter · #3 ·
OK,

Thanks for the info. So in this time of almost $3 a gallon of gas it's worth the 3 miles or so difference in gas mileage? I'm hoping that this is worst case scenario losing about 3 miles per gallon.
 

·
Registered
Joined
·
151 Posts
What ULTRACLYDE said were my thoughts per word. However I would add. A hot girl X her sister + her friends freinds = a good time for me X 3 = 4 give or take an hour or two.
 

·
Registered
Joined
·
5,820 Posts
clubt said:
OK,

Thanks for the info. So in this time of almost $3 a gallon of gas it's worth the 3 miles or so difference in gas mileage? I'm hoping that this is worst case scenario losing about 3 miles per gallon.
Shoulda got a Toyota if you were worried about gas milage/prices :weeps


Great explanation ultraclyde
 

·
Registered
Joined
·
151 Posts
Discussion Starter · #6 ·
Stoenr said:
Shoulda got a Toyota if you were worried about gas milage/prices :weeps


Great explanation ultraclyde
Thanks for your valuable input.:doh:
 

·
Registered
Joined
·
5,820 Posts
hehe, I could'nt help that one. ultraclyde gave all the input already, someone had to be the class clown.
 

·
Registered
Joined
·
151 Posts
Discussion Starter · #8 ·
No problem.

In all seriousness though, the gears are well worth it in your opinion?
Do you plan on putting 4.10's in your car when it comes in?
By the way, awesome color choice on your new ride!
 

·
Registered
Joined
·
886 Posts
I'm probably not doing gears in mine, at least not for quite a while. I drive about 50 mi roundtrip to work every day in mixed conditions. I'm sure I'd love the power, but I just can't afford it right now. Heck, mine's still box stock at the moment, and I'm pretty happy. Course, I've only had it a little over a month. For me? Not worth it right now, but a couple years down the road...few more raises at work...I'm thinking 3.73 and a supercharger. But then, you're talking premium pump gas and some SERIOUS fuel consumption when you're on the pedal.


I was driving a 1970 impala with a 4bbl 350, tuned pretty hot. I got an average around 15mpg (2.56 rear gear), but had to run premium. I'll enjoy what little advantage I have at the pump right now.
 

·
Registered
Joined
·
5,820 Posts
I do plan on it at some point. My work commute is less than 4 miles.

but will be everyday driver.

Not sure who your were aimin at on the choice of color, but if it was me, I hafta agree, its the best color :) Just seen it in person yesterday for the 1st time.
 

·
Registered
Joined
·
886 Posts
Stoenr - The color was for you, I think. I actually went to the dealership to order an 06 in that color, but they had the silver 05 someone had refused delivery on, and it had every option I wanted. I'm happy with the silver, but the tungsten is gorgeous.
 

·
Registered
Joined
·
5,820 Posts
Yeah, I dont think there is a bad Mustang color from Ford. Maybe a few more optional colors wouldnt hurt.
 

·
Registered
Joined
·
9 Posts
Just looking around saw this thread thought I would chime in. I have 4.10's. First of all imo Awsome Mod!! As far as speed I've had mine up to about 135 with more to go, have'nt topped it out because i don't see the need. Gas mileage 14 to 15 around town (being good of course:naughty ) highway around 17 to 18. The best part about it is the low end 0-60 snap its sweet:laughlitt :laughlitt :laughlitt . Hope this helps:wavey

Rog
 

·
Registered
Joined
·
183 Posts
clubt said:
Looking to change gears to 4.10 in an o5 gt vert:

How much will I lose in top speed? For instance If the car goes to 143 with the speed limiter will the car only go 120 now?
clubt,
This may help.

http://www.f-body.org/gears/

GT Five-speed manual (Tremec 3650)
1st: 3.34
2nd: 2.00
3rd: 1.32
4th: 1.00
5th: 0.68
axle ratio: 3.55

V6 Five-speed manual (Tremec T-5)
1st: 3.75
2nd: 2.19
3rd: 1.41
4th: 1.00
5th: 0.72
axle ratio: 3.31

GT & V6 Five-speed automatic (5R55S)
1st: 3.25
2nd: 2.44
3rd: 1.55
4th: 1.00
5th: 0.75
axle ratio: 3.31
 

·
Registered
Joined
·
435 Posts
ultraclyde said:
As for gas useage, it will be theoretically equal to the percentage increase in RPMs at a given speed. This, in turn, is a direct mathematical relation to the change in gearing. works like this:
(4.10-3.55)/3.55 = % of gearing increase = % increase in rpms for a given mph. It also more or less = the % increase in fuel consumption. "More or less" because effective load on the engine will differ because of the gearing change. Also, throttle mapping across the RPM spectrum differs, so fuel delivery is slightly different. If you reflash a custom tune to account for the gears, all this goes right out the window. All of this is null and void unless you drive PRECISELY the same way. I'd bet a big part of the declining mileage you will experience is the sudden fondness of the gas pedal for the floor board.:hihi: :hihi:

having said all that, if you go from 3.55 to 4.10, and were getting 17.5 mpg, you will then get 14.8 mpg. In a mathmatically perfect, theoretical world.:shigrin

bottom line: mileage is worse. Do the gears and enjoy the heck out of it.
Ultracyde, good thinking, but it's the wrong concept. I thought the same way until someone explained this to me, and it makes a lot of sense! Gas consumption is indirectly related to RPMS and Torque, it is directly related to horsepower. Since horsepower is effectively torque x RPM, in theory with different gears, there would be less torque, but proportionally more RPM, thus using the same amount of horsepower (gas) to move the car at a given speed. This is in a perfect world, but in reality, more RPMs through the tranny generate more heat, more resistance in the engine itself, so it should be slightly worse, but not a huge difference.

Consider this: with a full tank, most cars will idle about 30 hours without running out of gas, this is about 7-800 RPM. So, using that logic, cruising down the highway at 1600 RPM, the car should run for 15 hours, right? No, because when idling, it's both not spinning fast, but putting out almost no torque, meaning it's producing very little horsepower and only burning enough gas to overcome internal resistance in the engine.
 

·
Registered
Joined
·
5,003 Posts
Got fuel yesterday (dang 93 oct tune!) So as I drove to work I put up and reset my MPG disp for kicks... low and behold, 69 MPH on CC she was showing ~28 MPG! And not for a while, for the fist 20 minutes!

Then I crossed the bridge and went up the KY hills... dropping, dropping, dropping... all the way down to 18-19 MPG, mind you this is an average from my reset 25 minutes before. I'm going to shift down to 4th and put her in CC and 69 MPH today and see if there is a diff uphill...

Why I post here... well, if it is so rough on them uphill, high TQ, gearing will help MPG in sertain situations...!!

I don't think you cruisers, short drive, no higghway drive, etc. guys and gals will notice much from 4-10's...??
 

·
Registered
Joined
·
151 Posts
Discussion Starter · #17 ·
C said:
Just looking around saw this thread thought I would chime in. I have 4.10's. First of all imo Awsome Mod!! As far as speed I've had mine up to about 135 with more to go, have'nt topped it out because i don't see the need. Gas mileage 14 to 15 around town (being good of course:naughty ) highway around 17 to 18. The best part about it is the low end 0-60 snap its sweet:laughlitt :laughlitt :laughlitt . Hope this helps:wavey

Rog
RogMagic
Thanks for the insight. Just wanted to make sure that it didn't bring speed down to 120 or something. MPG I guess I can live with although the 93 tune on my Xcal2 is a killer at around 2.90 a gallon. I'm excited to feel that 0-60 snap next week! Do I really need to baby the car for the first 500 miles after I get the mod done?
 

·
Registered
Joined
·
357 Posts
Top speed will not be effected by that much. 140 is possible.:evillol:

My cost to install them was $250....and I paid $170 for the part (shop around and you should be able to find it close to that...some have the part as high as $210 or so).

Get a tuner as well. You should ( I did) get better gas mileage with a tuner, offset the increase for premium (maybe)...and be able to recalibrate for the 4.10's. If you baby it you can still get excellent gas mileage with the 4.10's. I averaged 23+ mpg from Cinci to Columbus (pretty flat)...going 75 to 80 with my 4.10's. That is doing a few WOT's every now and then too.
 

·
Registered
Joined
·
5,003 Posts
So to continue my MPG test I drove the same way at the same speed yesterday and today. I thought there was going to be a diff doing the uphills in 4th at about 3200 RPM, 1000 more than in 5th... but not this much... the average was 7 MPG better downshifting for those two miles uphill! Amazing! Two minutes outa a 35 minutes trip changed the average MPG from 17.8 to 24.5 just by taking the BIG hill in 4th instead of in 5th, both time with the CC locked at 69 MPH! So 4-10 gearing is prolly not too bad for fuel if it's not all flat and 70 MPH...
 
1 - 19 of 19 Posts
Top