For my ZZ502 with Tremec TKO-600, I have to decide on either a 3.73 or 4.11 rear end ratio.

Here's the table of ratios I came up with based on 255/40/17 tire, 3.73 ratio, and 2.87/1.89/1.12/1.00/0.64 gearsets.

If I went to a 4.11, I'd wind up close to 2500rpm at 60mph, which does seem a bit high. Do you think this is "enough" gear for a street/strip car? It does look like it doesn't come out of 1st until 40mph, which seemed a little steep to me.

Anyone have thoughts? 4.11 seems tempting, but that would push the crusing RPM up to 2500 on the highway, which would almost defeat the whole overdrive thing.

Thanks,
Dave

1 2 3 4 5
0 0.0 0.0 0.0 0.0 0.0
500 3.4 5.1 8.6 9.6 15.1
1000 6.7 10.2 17.2 19.3 30.1
1500 10.1 15.3 25.8 28.9 45.2
2000 13.4 20.4 34.4 38.5 60.2
2500 16.8 25.5 43.0 48.2 75.3
3000 20.1 30.6 51.6 57.8 90.3
3500 23.5 35.7 60.2 67.4 105.4
4000 26.9 40.8 68.8 77.1 120.4
4500 30.2 45.9 77.4 86.7 135.5
5000 33.6 51.0 86.0 96.3 150.5
5500 36.9 56.1 94.6 106.0 165.6
6000 40.3 61.2 103.2 115.6 180.6
6250 42.0 63.7 107.5 120.4 188.1

This is just my opinion, and I'm not sure what that gear ratio chart is trying to tell me, but most people want about a 10:1 overall 1st gear ratio. And I would say about 1800-2000 RPM cruising speed. From what I hear a big block has lot's of Torque and low gears are not needed. I would seriously consider 3.42's or 3.08's depending on what axle you have.

A friend of mine just put 4.11's behind his 6 speed this spring, and I've had my 3.73's behind my 200-4R for 4yrs. I really like the 3.73's the give me a good launch and I still have a nice highway cruise speed. He kinda' likes the 4.11's with his 6 speed. It's a little too steep in 1st. With your gear ratios and the 4.11's my calculation come out around 2300 at 65.

Differential Gear = 4.11 to 1
Transmission Gear = 0.64 to 1
Tire Diameter (Inches) = 25.00
Vehicle MPH = 65
Computed Engine RPM is 2299With 3.73's you get.

Differential Gear = 3.73 to 1
Transmission Gear = 0.64 to 1
Tire Diameter (Inches) = 25.00
Vehicle MPH = 65
Computed Engine RPM is 2086Now first gear you get.
3.73x2.87=10.70 to 1
4.11x2.87=11.80 to 1

It all comes down to how and where you plan to drive. If this is a true street/strip car that doesn't see long trips then you should be running the 4.11's. If you occasionally take it to the track and just want a fun ride around town that's also nice to take out on the open road to shows or cruises then you need to stay with the 3.73's.

I was just looking at this sight

http://www.chrismans.com/Calculators.html

which indicates that assuming your Camaro with you and your BBC weighing around 3900 pounds with the avg 502 putting out 540 horse and running your 25" tall tires you will be clicking off a quarter mile at about 5800 RPM in 10.82 sec @121.1 if you were using your ideal gear ration of 3.56:1. Chevy used to make a 3.55 gear for the 12 bolt (out of production) but you may be able to find one on-line or through some one like big gear head a regularly contributing member.


Larger Dave

You can still get 3.55 gears from richmond. Thats what i have in my car. My personal opinion is unless your racing the car no need for 4.11s with all the torque that 502 is gonna produce.