3.55 vs 3.73 gears - Mustang

[ExecutiveHydra]

So. I have 3.73 gears sitting in my garage collecting dust. I have 3.55's on my car now. Would it be worth my time to switch them out? Any kind of noticeable performance gain that I would see?

[Boozshey]

What trans? Do you drag race?

[Solar]

When I had my Fox Body (90GT Auto) I found the 3.73 were great for launching but still allowed highway speeds with no major issues. Of course mine was a AOD tranny, and that was the major reason I sold it. So my comments probably don't help much if you have a 5 speed.

[Boozshey]

If anything he has a 6spd... Assuming he's asking about the 2011 Mustang.

[Loren]

For autocross, which option gets you to 60 or as far beyond as possible without shifting to 3rd?


Sent from my phone with Tapatalk. Expect even more errors than usual!

[ExecutiveHydra]

The car is an Automatic. I do use it to drag race, but I also don't want too short of gears for AutoCross either. The transmission is Performance/Race tuned right now but I can change that whenever I need to if my shift points are bad, and if it's down shifting when I don't want it to. Loren, 3.55's get me to 60 before third if I am heavy footed on the gas, otherwise it shifts up frequently.

[twistedwankel]

5% rpm gain (or loss on top of gears) if I did the math right. I can change more than that with tire diameters quicker and go back and forth easily.

If you aren't all ready routinely beating Shamu @ autocross with it's 3.27 and AOD with a redline of 5600, 3150lbs + driver, 200HP and 285 torque, stock 15.1 second quarter mile times? Well you should be. Shamu isn't even close to an optimized race car - yet. (Stock I can run up to 45mph in 1st and 70+ in second so I hold it in one of those gears as desired.)

Flat out Drag racing you benefit from 60ft times and quicker ET meaning weight loss, nitrous, drag radials, gearing. Bracket drag racing you want consistency (serious record keeping on conditions) and quick reaction times period - but drag radials can help there too avoiding wheel spin.

The optimum shocks for autocross work almost the exact opposite from drag shocks that throw up to 90% of the front weight to the rear on launch. The optimum tires for autocross don't work well for drag racing as they are too wide in the front and don't flex in rear for launches. You can stand on an unmounted autocross tire off the rim and it won't collapse.

I used to make decent money bracket racing a dedicated (driven to events) stock turbo AOD car. Got tired of driving 3 hours only to get a rain check with a drizzle. Discovered autocross. Only go to Drags maybe once a year or two for a test and tune to see how car is running. I better always see a 15.1 or close to it or need tuneup.

Hope that helps with your plans.

[Boozshey]

Sorry, for the late reply....

Anyways, when did you put the 3.55's in the car? I didn't think Ford offered them as an option in 2011.

If you didn't order it with it or you didn't get them installed you might have 3.15's.

If that's the case the step to 3.73's would be worth it. But I know I wouldn't go 3.55's to 3.73. Just not enough to gain. And the risk of getting noisy gears isn't worth it either.

Are you 100% sure about the 3.55's?

[ExecutiveHydra]

Bruce I put 3.55's in the car after I got bored of the 2.73s. That about about June of this year. A 5% difference for a couple hour job really isn't worth my time at this point then. Since I am already in the M2 class as is, since I modified prior to joining AutoCross, seemingly if I want to run both types of events in the car it looks like I really need to add adjustable shocks and struts to the car in the future.

So what I am coming up with, leave the gears the same, not worth the change, drive the car better(because Doug said I should be able to beat him ), and in the future get adjustable shocks and struts so that the car is efficient in both types of events.

Thanks for the help everyone!

[jesup16]

Adjustable shocks (like Koni's) aren't going to enable you to switch between AutoX and drag racing. There is a huge difference between drag racing adjustable shocks and autoX adjustable shocks like SA/DA Koni's & others.

If it were me, I'd get something for auto-x and just 'deal with it' when going drag racing. Good thing about bracket racing is that you can dial in 20.00 and win! It's about consistency! I had a friend that won several events with a saturn. Slow as dirt but he was very consistent.

In regards to gears, I'd keep your 3.55's unless you are finding yourself shifting to 3rd. Not that drastic a difference and might actually be faster with a lower gear that has less tendency to spin the tires/less required throttle modulation.

[Boozshey]

Do what I did... Buy a different car for each event...

On the left... 5.8L w/ 3.6L blower

http://img.photobucket.com/albums/v637/ ... 00d4d8.jpg

http://img.photobucket.com/albums/v637/ ... 99eec0.jpg

[jesup16]

I have to agree with Bruce. Especially if you are of the competitive spirt. It's practically impossible to build a car that does both competitively. There are some very good cars and even better drivers in M2.

I'm not saying go out and buy a bunch of parts or even a car. I'd probably have an instructor / veteran co-drive your car to see how you compare.

[ExecutiveHydra]

I have to agree with Bruce. Especially if you are of the competitive spirt. It's practically impossible to build a car that does both competitively. There are some very good cars and even better drivers in M2.

I'm not saying go out and buy a bunch of parts or even a car. I'd probably have an instructor / veteran co-drive your car to see how you compare.

Drew drove my car at SPC and drove it a second faster than I did. It was pretty awesome. I need more seat time for sure, and it's also been helpful having people ride with me. Everyone should definitely take full advantage of that if they're new like me.

Overall, after doing some research I am going to take y'alls advice and set this car up for AutoCross (because its more fun) and just drag race it as is.

[Solar]

Drew drove my car at SPC and drove it a second faster than I did.

Drew drives everyone's car a second faster. No matter what you do to your car, if Drew drives your car, he will humble you, it might not be by a second, but he will most likely beat your best time in your car. It's just the way it is.

[Loren]

Freakin' Drew and his freakin' talent.

[blacksheep-1]

FWIW the fast guys driving normally aspirated 4 valves at the drags are running 4.56s. That being said IMO you probably should've gone from the 2.73 straight tot he 3.73s, but since you have the 3.55s I'd just live with them, the 3.55 to 3.73 is not that much of a change. I've run everything from 2.73 to 4.11s and it just depends on what the course happens to be that day on which is better (although an auto can always use a little more gear).
Concentrate on the driving, the rest will fall into place.