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Discussion Starter #1
Hey guys,

Pretty simple really. For now I am building the rear end and sticking with my T-45. Would 3.73s or 3.90s be best for a road course?

I would think 3.73s at this point.

Car is a 96 cobra
 

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There is a lot that goes into answering that question.

How tall are your rear tires?
How fast will you be going in the fastest straightaway on the track that you intend to run? How slow will you be going in the slowest turn? What does your torque curve look like?

I mostly run at Sebring and Daytona.

I have a T5 with the following gear ratios 2.95, 1.94, 1.33, 1.0, 0.8 and a 3.36 rear gear. My tires are 23.5 inches tall.

The slowest turn at Daytona is about 55-60 MPH, and on the fastest straight I am running about 165-170. At Daytona I only use 3rd, 4th, and 5th gears. On the slowest turn, I am kind of low in the rpms for 3rd gear, but shifting to second is inconvenient. Also, I am running out of rpms in 5th gear down the long straights. The car needs a taller rear tire or longer gear for Daytona.

The slowest turn at Sebring is about 35 mph and the fastest straight is around 150. Second gear is perfect in the hairpin, and the rpms are perfect on the long straights. I am really happy with the gearing for Sebring.

What I am trying to convey is this: The gearing that is optimal on one track won't be optimal for another. Pick the track (or portion of a track) that you want the car optimized for and go from there.
 

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Excellent answer, I was trying to explain the very same thing, didn't want to write a book. The main point being optimal gearing is anything but simple. That's why quick change gearing was developed.

Jay
 

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Discussion Starter #4
Very good information! Thank you! That does help and I will have to look a little more into that

Yes but I, nor most can afford a quick change gear setup.
 

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I run a 1996 4.6/T-45 and use a 3.27. For the tracks I run it's the perfect setup. (NASA National Champion in 2015). We hit 138-140 at one track which is just below the rev limiter....in 4th. If your tracks top out around 120-125 you can use 3.55s or maybe 3.73???. Whatever you do, avoid your 5th gear. They don't make aftermarket gears and it's a low .6X/overdrive gear that is useless on road courses.
 
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