gear ratio question - Ford Mustang Forum
 
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post #1 of 13 (permalink) Old 04-04-2011 Thread Starter
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gear ratio question

I am looking to do a gear swap to my 2007 V6 mustang. It currently has the factory 3.31's and I want to go to 3.73's. My first question is how much of an rpm increase will i see just driving around? Second, how much will this effect my gas mileage? I drive mostly in town but I do occasionally get on the highway on some road trips.

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post #2 of 13 (permalink) Old 04-05-2011
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i just want to let you know right now. this is not an inexpensive process and you take the risk of getting a bad gear install which will make the whole thing a giant waste of money. spend the money on a tune and cold air intake instead. then if that doesnt satisfy your need for better accel and throttle response then think about doing this mod. i am still paying divides for the crappy ordeal from my gear install. the other option is you buy an 8.8 rear-end with the gears you want already installed and find a good mechanic friend and make it a weekend project swapping rear-ends. the cost of a gear installed ready 8.8 rear end is about how much it is to pay for all the necessary parts and labor costs needed to put a t-lock and 3.73s in the rear end of a v6 7.5 rear-end.


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post #3 of 13 (permalink) Old 04-05-2011
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gas mileage loss for me was about a few mpgs, not too bad. rpms arent the isssue with the swap it will be the feeling of too much joy when slamming on your gas pedal to experience the thrill of acceleration.

2005 V6 Satin Silver Mustang
MODS:
Dual Exhaust w/X-pipe and PYPES BOMB exhaust w/FRPP cutouts, Shorty Headers, Tunable Induction CAI, BAMA 93 Race Tune, Coil Pack w/JBA Power Cables, Iridium Spark Plugs, 3.73 Gears w/T-Loc, Short Throw Shift Block w/poly bushings, Tokico Shocks and Struts, FRPP Lowering Springs, Steeda Camber Plates, UMI Lower Control Arms w/CHE Brackets, GT Anti-Swaybars, Project Headlights w/Splitters, Clear Corners, Blackout Grills w/Emblem, FanBlade Rims
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post #4 of 13 (permalink) Old 04-05-2011
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You can learn a lot with this.

Be very picky when choosing an installer. Try to find a shop that does nothing but rear gears.

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post #5 of 13 (permalink) Old 04-05-2011
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I forgot to tell you that the numbers that are in the calculator are for a v6 manual. Automatics are a little different. The autos will be a little lower rpm in overdrive. (5th)
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post #6 of 13 (permalink) Old 04-05-2011
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I just finished my first 500 mile trip with my 3.73 gears and CAI/tune. The MPG were about 1 mpg less at the most according to the trip computer. But the difference in passing and going up long hills was amazing and well worth the 1 mpg.

+1 on going with 8.8. I wish I would have done that now. The problem is that with 7.5 we are limited to the Motive gears and the can have issues with noise. They are cut different than stock. The stock gears are flat on the coast side and motive gears are triangular. My mechanic spent 3 days trying to get it right and it still has a slight whine on deceleration at certain speeds. Not bad really, the Eagle F1 are louder much of the time so I can live with it. But even with the minor noise the limited slip and gears make a huge difference and well worth the investment.
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post #7 of 13 (permalink) Old 04-05-2011
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I bought genuine Ford 3:73 for my 7.5. The Motives are noisy for sure but you can get Ford gears for a 7.5 in several ratios except 3:55.
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post #8 of 13 (permalink) Old 04-05-2011 Thread Starter
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Thanks for all the responces. I am not doing the install myself. The shop up the road from me is. For upgrading the 7.5 is a little cheaper for me and I really don't have the room for an extra rear to sit around. I already have headers, intake,tune,wires,and a coil. I also have a steeda strut tower bar,steeda swaybars,eibach pro-kit and an MGW shifter. I figured this would be my next step.
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post #9 of 13 (permalink) Old 04-05-2011
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Quote:
Originally Posted by great08 View Post
I bought genuine Ford 3:73 for my 7.5. The Motives are noisy for sure but you can get Ford gears for a 7.5 in several ratios except 3:55.
My Ford Ranger came with 4.10s in its 7.5 rear end. There is a 3.73 set available and a 7.5 t-lock. Ranger parts for the rear end should work fine in the Mustang.

2008 manual GT with deluxe trim, Edelbrock e-force, FRPP GTB Mufflers. 3.73 gears, Coast Ultralight Drive-shaft. 18" OEM Polished Bullitts, Webelectric Sequentials, XM built into the Shaker 500. Alarm and Escort RedLine.
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post #10 of 13 (permalink) Old 04-06-2011 Thread Starter
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I've heard alot of good things about Richmond gears
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Search under my profiles posts regarding this as I have provided what I believe is the most detailed breakdown analysis of 4.10s for our 4.0s.

Bottom line: I get 350-360 miles to a tank of gas all highway. I have never gotten under 300 miles on a tank (20mpg since I never seem to be able to get that last gallon outta there so this is 300/15 or 20mpg for that tank).

Gears is the second biggest bang for your buck if your looking to improve acceleration and basic burnout fun. The first being the tune.

Good luck dude.

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get the install done from a trusted shop who warranties their labor. also get the LSD while they set up your rear end. they shouldn't charge you much if anything to put that in, too. as far as gas milage goes you'll lose 1 or 2 on the highway and gain 1 or 2 in the city. if you do mostly city driving it's not really a big deal

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post #13 of 13 (permalink) Old 04-10-2011 Thread Starter
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Quote:
Originally Posted by johnnshepherd View Post
get the install done from a trusted shop who warranties their labor. also get the LSD while they set up your rear end. they shouldn't charge you much if anything to put that in, too. as far as gas milage goes you'll lose 1 or 2 on the highway and gain 1 or 2 in the city. if you do mostly city driving it's not really a big deal
Already one step ahead of ya, just ordered Richmond gears and a Ford Racing limited slip.
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