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Discussion Starter · #1 ·
Hi fellas, After I picked up my manual v6 a few months ago, I'm quite comfortable driving it in bay area's traffic now. But soon it's close to Thanksgiving so I'm considering about dumping some cash into this black hole of car modifcations.

The mod I'm gonna go with is rear gear, but I'm not sure what gear should I go with (I found out mine has a 2.73 during a liquid top-off two weeks ago). Judging by the fact that I do around 60% of city driving(included getting stuck on the fwy), should I go with 3.31 or 3.55(3.73 is a bit too much for me..)? . I really want to hear about you guys' opinion about it. Because 2.73 is just ...soo sloppy on the highway especially at 6th gear...
Also, may I ask how much did you guys spent on getting the gear swapped?
Any related/not so related answers are all greatly appreciated.
 

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I've driven 2.73, 3.31 (what I have) and 3.55..for me I would pick 3.55 or 3.73.

I don't do much hwy and I have fun on two lane blacktop. The higher ratios would make 3rd gear more fun at speeds I'll drive on public roads. Wih the 3.31 3rd is fun from 40-85....I would prefer those numbers a bit lower. The other hint is make sure the shop you have it done at has a good rep. I've read countless threads of folks having issues. I will say the change frome 2.73 to 3.31 is a huge improvement
 

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My Mustang came with the 3.31 gears. I felt they were normal and nothing special. I changed to 3.73 gears on my automatic, perfect in every way. I have another vehicle for trips and long drives. I do hit the interstate from time to time, 60mph is around 2,000 rpm. My local Ford dealer changed my gears, new axle seals and fluid for $550. I bought the gears from American Muscle.

If you do a lot of interstate driving, 3.55 gears would be a good choice. If you go higher than 3.31 you will have to buy a tuner so you can make the speedometer right :)
 

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Since you do some highway driving, a couple of questions you may want to think about are, "How fast do I drive on the highway?" and "How much RPM am I comfortable with on the highway?"

For reference, my 3:31's turn right at 3k @ 100 MPH. That means that 3.55's should turn a bit over 3200 @ 100, and 3.73's should turn almost 3400 @ 100.

At a more normal (and legalish) 75 mph, those numbers work out to be 2250 RPM for 3.31's, 2400ish for 3.55's, and 2550 for 3.73's.

If you don't drive over 75, then 3.55's or even 3.73's wouldn't be too bad on the highway. If you tend to run at *ahem* elevated speeds, then you might want to go with 3.31's.

Just a few thoughts from a guy that does a lot of highway driving with his 3:31's...
 

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On boy this is a endless discussion. Week after I had my gears I still wasn't sure I made the right decision. Automatic, 3.73 makes it a beast coming out of the hole. Gas mileage not so good.


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On boy this is a endless discussion. Week after I had my gears I still wasn't sure I made the right decision. Automatic, 3.73 makes it a beast coming out of the hole. Gas mileage not so good.


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I have an automatic with 3.73 gears too. With my 'Lund' tune I was showing 17.2 mpg on the computer display. I'm now running my 'MPT' tune and the computer is showing 23.9 mpg. Same in town roads with short trips. I don't know why my 'MPT' tune gets so much better gas mileage than the 'Lund'.
 

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Discussion Starter · #9 ·
Since you do some highway driving, a couple of questions you may want to think about are, "How fast do I drive on the highway?" and "How much RPM am I comfortable with on the highway?"

For reference, my 3:31's turn right at 3k @ 100 MPH. That means that 3.55's should turn a bit over 3200 @ 100, and 3.73's should turn almost 3400 @ 100.

At a more normal (and legalish) 75 mph, those numbers work out to be 2250 RPM for 3.31's, 2400ish for 3.55's, and 2550 for 3.73's.

If you don't drive over 75, then 3.55's or even 3.73's wouldn't be too bad on the highway. If you tend to run at *ahem* elevated speeds, then you might want to go with 3.31's.

Just a few thoughts from a guy that does a lot of highway driving with his 3:31's...
Well, The thing is, I typically do 75 or 80-ish on the fwy, although the speed vary depends on the situation, 100 or above is still rare occasion for me. One thing i'm curious about is do you shift more often to keep the car "quiet" running 3.31(relative term)?
 

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3.73 I can run 70-80 no problem....I'm a auto so shifting not a problem. Bought a pretty quiet exhaust no problem there. Gas mileage is what you may not like. Mine is not a daily driver.


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Either, but the Higher one would be more Fun.
 

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I find with the V6 when I am just cruising it needs to be at 2k rpm or there isn't any torque....that is 50 or so mph in 5th with 3.31. If I had 3.55 (or 3.73) I would just be in 6th.
 

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Well, The thing is, I typically do 75 or 80-ish on the fwy, although the speed vary depends on the situation, 100 or above is still rare occasion for me. One thing i'm curious about is do you shift more often to keep the car "quiet" running 3.31(relative term)?
Well, I have stock exhaust on the car, so it is fairly quiet no matter what. However, around town I usually shift by 2500 and keep it under 2000 when cruising, but like others have said it has to be over 2k to make any kind of power, and if I really want to go I downshift to get to 3k.

But, the 2.73 ratio will have the longest "pulls" per gear (increase in speed relative to increase in rpm) with the pulls getting shorter as the gearing gets deeper... so your around town shifting will be more frequent. But, skip shifting is a bit easier, too.
 

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So, you guys are getting either a little under 20 miles to the gallon and as high as 24 with 3.7. That's interesting. I have a 4.6 and I'm getting 24.7 around town. The only thing is, I bought the car used and don't know what gearing it has or mods. Sounds nice, but sounds can be deceiving. Guess I should take it into a shop and find out what's been done.
 

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But now you've got me wondering what my gearing is. I guess if I take it out on the highway and look at RPM at different speeds, one of you should be able to tell me what my gearing is. Be back in a couple of hours.
 

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So here they are. In 3rd gear at 75 MPH I am running at 4400 RPM
In 4th at 93.5 MPH, I am turning 4000 RPM
In 5th, at 100 MPH I am turning 2900 RPM.
Tire size is 235/55/15. I know, it's metric but I'm from Canada.
 
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