Rearend Gears for V8s on the Track

[YellowSnake01]

Quick question on gearing for you guys, maybe you can make suggestions from what your running:

 

The car: 2001 mustang cobra, 4.6 DOHC, 320 hp (more of an RPM motor), 5 speed, all stock, and im planning on getting rearend gears in the spring. What would be a good choice for rearend gears? i drive the car everyday, and i plan on doing a few more HPDE events this season.

 

I took it up to Lime Rock in CT this past Nov, and noticed with the 3.27s i spent most of my time in 3rd and 4th. Being told it was a more technical track, i figured my speeds were slower (fastest i got was 120, not bad for my first time on the track having to slow down early for brake fade haha).

 

For the swap, i was planning on going either 3.73s, 3.90s, or 4.10s. The more gear i go will be more fun for the street and accelerating out of the turns will benefit greatly, but will i be running out of gear or just plain beating on the engine on some of the straights of the faster tracks?

 

Any help/suggestions would be greatly appreciated. Thanks.

[FastSaleen]

Just a thought, but why not go with a 3.55 rear end - especially if you still want to drive the street. I run a 1988 Saleen Mustang with a 325+ HP 5.0 under the hood. I won the 2004 Ohio/Indiana TTB championship with this car. It has a D.T.S. Detriot Locker 3.55 rear end - great off the corners and still mild enough to keep the car on the ground when driving on the streets. I don't think I would go any higher than a 3.73. I am perfectly happy with the 3.55. If and when the 3.55 breaks, I might go to a 3.73, but I don't plan on going any highr than that. The car is enough of a workout without adding extra shift points to each lap.

[Cobra-R]

Brian,

Those mod motors like to rev, whole different logic compared to the pushrod motors.

 

Yellow,

I had a 01 Cobra that I used for the track, 4.10's worked just fine for me. I could actually get a faster top speed out of that car (at brainerd 5200' straight) than I can in my 95 Cobra R. I would go a minimum of 3.90's and nothing more than 4.10's if I was you.

 

Brian

[YellowSnake01]

Cobra-R,

Now with running a 4.10 at a high speed, how did the engine like doing it? What would be your limit on how high you would bring the car, either RPM or MPH. I'm a little paranoid about holding the engine at such a high RPM for an extended period of time on a stock motor, especially since I'll have to drive it to work everyday.

 

Part of me likes the 3.73s because of the fact that I wont be revving the heck out of it, but if the 4.10s won't be a problem it would make most sense to go with those.

 

On a sidenote, anyone notice much of a difference in gas milage for driving everyday? It's not a major concern for me, but something I'd like to keep in mind.

[johnbasf]

I ran 4:10's. 4th gear with those gears was @ 128mph at 7k rpms. It all depends on the track as far as running out of gears. VIR and Summit Pt's long straights would force me into 5th gear.

[Cobra-R]

Cobra-R,

Now with running a 4.10 at a high speed, how did the engine like doing it? What would be your limit on how high you would bring the car, either RPM or MPH. I'm a little paranoid about holding the engine at such a high RPM for an extended period of time on a stock motor, especially since I'll have to drive it to work everyday.

 

Part of me likes the 3.73s because of the fact that I wont be revving the heck out of it, but if the 4.10s won't be a problem it would make most sense to go with those.

 

On a sidenote, anyone notice much of a difference in gas milage for driving everyday? It's not a major concern for me, but something I'd like to keep in mind.

 

John is right, on long straits I would go to 5th as well. I don't think 3.73's is enough of a change on these cars to make it worth it.

 

mpg probly dropped a couple miles per gallon, can't say I really checked it since the car wasn't a daily driver.

 

Brian