[37mm]

I understand this is a highly debated and old argument within the Mustang world.

In a couple weeks, I'm getting my 02' 7.5 swapped out for a 8.8 from a 04' Mach 1. It comes with the stock 3.55. But I was wondering if I should upgrade them to 3.73s.

I've done at least a little research on the pros and cons between the 3.55's and 3.73's on my end.

From what I've gathered: (excuse me from my lack of knowledge, I'm still learning which is why I brought this up to you guys)

3.55's are good for the daily driver and a little mpg friendly. Top end friendly.

3.73's have a very noticeable boost in acceleration, but effect your MPG. You'll also sacrifice some top end speed.

My questions are:
Regardless of which ratio I go with, even with the 3.55's will there still be a noticeable difference from stock? I'm assuming the combination of gears and a T-lock will still put a dumb smile on my face.

My driving habits:
The majority of my driving is within the city. But I at least drive down the highway to visit friends and fam at least once or twice a month. The round trip is around 200 miles on a 60-70mph speed zone.

I'm not much of an aggressive driver, but I wouldn't mind an extra kick in my daily driver.

There are LOTS of ricers in my town. And I'd like at least some leverage against the never ending onslaughts of fart-cannon-fly by's.

Another factor:
My folks are about to move down to California and I'll be residing in Washington State still for school. I'm not sure how many times I'll be visiting them down there, but I think this should be a factor on my decision also.

Will the mpg change be major with the 3.73's? What are you guy's getting in your Mustangs? City/HWY? (average)

What's your guy's thoughts?

Keep the 3.55's? Or screw it! Go with 3.73's. I'd like VALID thorough reasons based upon your opinions. Not just: "Go with 3.73" one liners.

Thanks!

[Dave]

What is your gear ratio now? Any idea of rpm at 70 mph?

Just guess for now I'd stick with the 3.55's in the new rear and see how you like them.
Dave

[37mm]

Originally Posted by Dave

What is your gear ratio now? Any idea of rpm at 70 mph?

Just guess for now I'd stick with the 3.55's in the new rear and see how you like them.
Dave

Hey Dave.

I'm currently running the stock gear ratio my 02' V6 came out with. I bought the 8.8, since it came with both the T-lock and 3.55's off the bat. I was tired of the one wheel hop and wanted the two wheel peel.

RPM-wise at 70-75, I drive like a granny and like to keep things quiet and cruising on the highway usually. I don't know the exact range. I'm thinking between 2500-3000? If that sounds lame, like I said, I'm not sure exactly. Lol.

[Dave]

I'm some on here would sure know what the stock rear ratio is. There should be a small metal tag attached to one of the bolts on the rear end cover that looks like this. It has the ratio info on it, that and tire size will give what your rpm's are.
Dave
http://www.therangerstation.com/tech...es/AxleTag.gif

[Dave]

Double post for some reason!

[Playboiplay]

Originally Posted by Dave

What is your gear ratio now? Any idea of rpm at 70 mph?

Just guess for now I'd stick with the 3.55's in the new rear and see how you like them.
Dave

A stock mustang should be running 3.27s

I'd recommend trying out the 3.55 gears for about a month to get a feel of the difference over stock. If you like them, stick with em. However, if the mod bug bites you (...and I'm sure it will), consider going up to 3.73 or possibly 3.90 since you'll have an 8.8 rear end. One BIG upside of having a GT or incorporating GT parts is that there's a much larger selection of aftermarket parts available for them. Hopefully they'll show more love for the V6 in the future.

[37mm]

Originally Posted by Playboiplay

A stock mustang should be running 3.27s

I'd recommend trying out the 3.55 gears for about a month to get a feel of the difference over stock. If you like them, stick with em. However, if the mod bug bites you (...and I'm sure it will), consider going up to 3.73 or possibly 3.90 since you'll have an 8.8 rear end. One BIG upside of having a GT or incorporating GT parts is that there's a much larger selection of aftermarket parts available for them. Hopefully they'll show more love for the V6 in the future.

The original plan was to try the 3.55's to see if I liked them. And believe me, if the mod bug didn't bite me, I wouldn't be spending a pretty penny on a new 8.8 rear end! Which is why I was wondering about the 3.73's. This debate has been running in my head for weeks and was only fueled by it by other posts relating to it.

I know for sure when the 2011 V6 Mustang Rolls out with it's supposed 315HP V6. The market is gonna be big. And that's when I'll know for sure my sixer is outdated.

[Cusp]

The difference between 3.55 and 3.73 is only about 5%. A small change. Looking at the T5 transmission, it appears that the V6 with 3.55s will be similar to the GTs with 3.73s.

As far as top end speed if you have the horsepower to push the air....

Try the 3.55s you can always change them later.

[37mm]

Originally Posted by Cusp

The difference between 3.55 and 3.73 is only about 5%. A small change. Looking at the T5 transmission, it appears that the V6 with 3.55s will be similar to the GTs with 3.73s.

As far as top end speed if you have the horsepower to push the air....

Try the 3.55s you can always change them later.

That's what I've been reading from other posts relating to this topic. The differences RPM wise between the 3.55's and 3.73's from what I read were I believe around 300 RPMs. Which didn't seem like a very dramatic difference.

I think I'll try them out and see what happens.

[2Manystangs]

Go with the lower gears (3.73) if it's too much you can always put larger rims/tires on it to raise the effective gear ratio...

[37mm]

Originally Posted by 2Manystangs

Go with the lower gears (3.73) if it's too much you can always put larger rims/tires on it to raise the effective gear ratio...

I've been hearing about how larger wheel/tire size(s) effect the gear ratio. But I have little knowledge of the pros and cons of them.

I'm currently riding on 17x9's (245/45/95W) Would that be sufficient for what you were talking about?

Can you give me a little input on how 3.73's or pretty much how gear ratios are effected by wheel/tire size?

[Cusp]

Originally Posted by 37mm

I've been hearing about how larger wheel/tire size(s) effect the gear ratio. But I have little knowledge of the pros and cons of them.

I'm currently riding on 17x9's (245/45/95W) Would that be sufficient for what you were talking about?

Can you give me a little input on how 3.73's or pretty much how gear ratios are effected by wheel/tire size?

The ratios of the gears are not effected by tire size.

The drive train functions as a whole to change angular velocity to linear velocity. The final "gear" in the train is the tires. Something like this.

Engine RPM X Transmission Ratio X Rear End ratio gives your axle RPM. Axle RPM X wheel circumference = distance per revolution per minute. Times 60 minutes to get hours.

The end game is how many times does the engine go around for a given distance traveled.

[wrenchman]

Here's the basic formulas I use to make gearing calculations, and they've proven to be pretty accurate (providing you're plugging accurate numbers into them):

MPH= (RPM x Tire diameter x 3) divided by (trans gear ratio x diff gear ratio)

RPM= (MPH x trans gear ratio x diff gear ratio) divided by (tire diameter x 3)

Gear Ratio= (RPM x Tire diameter x 3) divided by (MPH)
(this gives the final ratio which is a combination of trans gear and diff gear)

Tire Diameter= (MPH x trans gear ratio x diff gear ratio) divided by (RPM x 3)

Using these formulas I actually calculated and made up a chart for myself showing the engine rpm at different road speeds in different gears (T5 trans) with four different diff gears. The calculated numbers were pretty much dead on with my tach and speedo readings on my current setup. Might be worth doing the math to actually get an accurate idea of what you could wind up with.

[ESG-642T]

3.73s or 4.10s

.....If your not planning on going turbo I would say 3.73 at the least.

[shinerstang]

If you are at 3:55's now, it will not be a huge jump going to 3:73's. I would say to stick with what you have, and save the cash for another mod. The price of the gears + installation is not cheap.....