mustangfan123

I have a manual transmission 2007 gt/cs that is street driven most of the time and has not seen track time yet. I am not sure on which gearing to go with. What do you think would be best for my car?

281GT

Go with the 4:10 ratio. Our Mustangs have a pretty tall over drive. OD with the tremec 3650 is .68 so if you multiply the 4.10 x .68 you still have a final drive ratio of 2.78 which is still a pretty tall final drive ratio. There are just no downside to 4.10s when you have a tall over drive like this. You will see tremendous gains in responsiveness in all gears with no loss in top end speed.
Some people will argue the no loss on top end speed. Consider the following facts.
Assuming you have a 3.55 multiply by x .68 = 2.41 final drive.
With a ratio that tall you will never even come close to maxing out your rpms in 5th gear. With this setup 6000 rpm in 5th gear is 202 mph assuming a P235 55R17 tire. Obviously this is not going to happen for a number of reasons I will not mention here.
However take your final drive ratio of 2.78 which is what you will have with the 4.10s and at 6000 rpm you will be doing 175 mph. Still never going to happen. Even with the 4.10 gears you still won't come close to hitting redline in 5th gear.
Your rpms at highway speeds won't increase enough to cause any driveablilty issues. You may see a very small loss in highway fuel economy but the performance gains are well worh it.
As for the 3.73s, unless you have the 3.31 ratio now you won't see enough of an improvement to make the cost of a gear change worth your while.
Go with the 4.10s. Many people have and they are happy.

FLAstangx3

Now that is about the best write-up reasoning I have ever seen on a forum. Most just believe that the 3:73 is the perfect "driving' gear ratio, and if I had an auto, probably would settle for that also. But as you say, our S197 are 'tall'. so why 'settle'. If you're going to do it, do it right the first time. You'll be glad you did. (Oh yeah, one other thing. You won't have to look back either!)

GRAYPNY

4:10 gears are great for our 5 speed manual cars. I can't comment on the auto but I have never regreted putting in the 4:10 gears and I still have to smile when I get sideways in 2nd.

281GT

The auto's OD ratio is not quite as tall. The auto has an OD ratio of .71
So the 3.90 gear would be best for that which will give you a final drive of 2.76. Plus the auto's first 3 gears are more closely spaced and they don't peform quite as well with 4.10's overall. In my opinion the optimal gear for the auto is a 3.90 but they are a little harder to get as there are fewer maufacturers making 3.90 gears for the Ford 8.8

SteelTownStang

What do you have now? If 3.31, go with 3.73. If 3.55, then go with 4.10

mustangfan123

I am not sure which gearing I have currently, I will have to look at the sticker on the rear axle.

BuzzyStang05

Ok, stupid question: Going from 3.55 to 4.10, spirited driving aside, when driving in town w/ low RPM launches, is there a difference in clutch technique to avoid bogging? That is, with a 4.10 do you slip the clutch more or less to get the clutch to smoothly engage? Or does it even make a difference?

AFBLUE

I've always been fond of the idea of the 3:90s. For me, 4:10s have a little too high rpms at interstate speeds.

281GT

Not a stupid question at all. The numerically higher your final drive ratio is the LESS you will need to slip the clutch to get moving. Numerically higher gears are actually easier on your clutch. Think of it as being the same as starting off in 1st or 2nd. You can start off on second but you will need to slip the clutch more. The more slippage the more friction, heat and wear.

MTAS

Yes, 4.10's all the way, regardless of whether you race it.

BuzzyStang05

Thanks - I saw a demo on Speed last weekend and was beginning to think that it would be easier to slip on a 4.10.

All this time my crazy brain was trying to theorize the '07 manuals went to a 3.31 to make it easier to drive/launch in traffic - but I guess it's just me finding low RPM launches with the 3.55 a pain in the butt...

So, with a 4.10, I might actually find getting up my steep but short driveway easier? Hill starts also?

Is there any difference in feel in trans-braking - smoother or harder?

281GT

With 4.10s you will find all starts noticably easier. It will really help getting up that steep, short driveway.
You will also notice improved engine braking on downwhifts which means less wear on your brakes as well.
The ONLY reason Ford went with 3.31 gears on some of these cars was for a slight improvement in highway fuel economy.
In my opinion the 3.55 ratio isn't bad but it's certainly not optimal. If you've got a manual a 4.10 gear is one of the best mods you can do to these cars.
Trust me it will make it seem like a different car it makes that much of a difference in performance and it's actually easier on your clutch.

mustangfan123

Hey guys, I have an update now. I finally looked under the car today and it said 3:31 Gears on the Rear End Girdle Sticker. I guess I should go with 3:73's like I planned originally cause I have 3:31's.

neil07gt

How are 4.10s for normal driving on wet pavement--such as starting from a stop at a red light in 1st gear? Is it too easy to spin the tires? Do you sometimes start from 2nd gear when on wet pavement?

tom281

I have 4.10s, with stock 17" Pirelli tires...... and a Vortech blower. I've driven the car alot over the last week in the rain or on wet pavement atleast, and it was still very controllable. Just as always, if you give it alot of gas, then yes you're gonna spin but if you're mindful of what you're doing, you'll be fine.

On a related note, 4.10s on dry pavement make it possible to start in 2nd gear relatively easily.

Just to clarify, I'm referring to the manual trans..... don't know how they run with an auto.

ken3030

just want to comment on 4.10s and an auto I have this setup and it is a DD on the highway I run about 80 mph at 3000 rpm. I had 3.73 and did not like how it launched at the drag strip, but on the freeway the 3.73 much better. If you want track performance the 4.10s if you want highway use the 3.73s much better IMO. but like I said I have an auto if I had a 5speed would for sure go 4.10s.

Cowtown

What was it about the track launch and the 3.73 that you didn't like Ken?