Which rear end ratio to use...99 Cobra

[Cobrared03]

I got my 99 cobra set up for AIX, this will be my first year driving it. What rear end ratio would be best to use? I kept the stock T-45, any recommended swaps?

[99cobra2881]

Is the car making real AIX HP or above AI HP?

 

What tracks are you going to run?

[Cobrared03]

Well funny you ask that...it's above AI HP, I don't feel it will be as competitive in AIX but I came from SCCA and already have Hoosier all over the place. AI only exepts Toyo tires. Are there any other classes I can fit into that might be a better fit? Performance Touring maybe? The tracks I'm looking to run this year are Watkins Glen and Mid Ohio, possibly NJMP.

[Smike]

I have a T-45 in my CMC car with OE gears. Running a 4.10 to optimize what I have for the tracks we see.

 

http://www.f-body.org/gears/

 

http://www.ttcautomotive.com/English/products/T-45.asp

T45 -- 3.37, 1.99, 1.33, 1.00, 0.67

 

How much power are you making (dynojet)?

 

There is PTB and the ST3 class that you might fall into.

[snakebit]

Above AI horsepower and t-45 do not make for a long lasting relationship

My advice would be to calculate anticipated top speed (at the tracks you run) in 4th gear, and choose rear gear accordingly.

For example 6500rpm in 4th gear (1:1) with 3:55 rear gear and 275/40/17 tire, gives about 140 mph

John

[99cobra2881]

I was in the same boat, came over to NASA from racing SCCA ITE, had hankooks and badged the car as AIX. I got some tire help from a few fellow AI racers and rebadged the car AI.

 

Use up the hoosiers and have fun in AIX. Youll get some great racing in with the AI guys.

 

My race car has 3.73s but I have run 4.30s in my open track car (stockish 99 Cobra w/ t56) and the 4.30s were a good gear for the low hp of the '99 cobra and the nature of the tracks around here.

 

Depending on your cars RWHP that will be the main factor in what gears you need.

 

What gears are in the car now?

[Cobrared03]

It's about 411 HP right now

[Cobrared03]

With 4:30 rear. Was just hoping it wouldn't be too tall.

[Maynor]

If you're running Mid-O, Watkins and NJMP, you'll be limited to to about 120 mph top end with the T45 in 4th. 5th is worthless. 3.73 or 3.55s are the way to go. If you're already running 411 whp, 3.55s are probably ideal.

 

On my old 99 Cobra, I use to run 4.10s making 525 whp at NJMP, Watkins and VIR. I pretty much got trumped on the straights with that gearing. Great for pulling out of turns but worthless for the straights.

 

John

[Cobrared03]

Thanks for all the insight. Looks like I'll be doing a gear swap soon, won't be a bad idea to open her up and check it all out anyways.

[wpbcobra]

I am running a 97 cobra with a tko 600 and currently have 373 but i am going to 410s the 373 just dont help enough getting out of the hole.

[Cobrared03]

How much HP are you making? The 3.73 isn't enough? I was thinking 3.73 might be just perfect.

[wpbcobra]

How much HP are you making? The 3.73 isn't enough? I was thinking 3.73 might be just perfect.

 

My car is making 335hp and 327tq.

[TurboShortBus]

Are there any other classes I can fit into that might be a better fit? Performance Touring maybe?

With the 411 hp you mentioned earlier (assuming that is rwhp), and assuming that you are in the neighborhood of 3300 lbs race weight, you are right around the 8.0:1 weight/power ratio for ST2 or TT2. Hoosier contingency is available in both ST and TT.

 

Mark