Diff Ratio advice....is this a good choice

[cluxford]

Guys, after some views......

Need to decide on diff ratio

BBC 632 cubes
makes peak power (torque curve) at 4300 RPM (825 Hp at flywheel, 816 Nm of torque)
Turbo 400

I'm thinking a 3.4:1 ratio

Transmission
1st Gear 2.48
2nd Gear 1.48
3rd Gear 1

Diff ratio 3.4

Tire Diametre 28 inches (17in rims with 325 x 45 tires)

Final Ratio
1st Gear 8.4 to 1
2nd Gear 5.0 to 1
3rd Gear 3.4 to 1

1st Gear
10 MPH or 16KPH = 1012 RPM
20 MPH or 32KPH = 2024 RPM

2nd Gear
30 MPH or 48KPH = 1812 RPM
40 MPH or 64KPH = 2415 RPM

3rd Gear
50 MPH or 80KPH = 2040 RPM
55 MPH or 88KPH = 2244 RPM
60 MPH or 96KPH = 2448 RPM
70 MPH or 112KPH = 2856 RPM
75 MPH or 120KPH = 3060 RPM
(KPH cause I am in Australia and we work in kilometres)


Car will be street driven only....3.4:1 gives good RPM range across reasonable speeds and some up my sleeve if I want to hammer it....

Any views ?

4.10 ratio would see RPMs go up by 200 in first gear and 400 in 3rd gear
a 2.4 ratio would see a drop in RPMs by 200 in 1st gear and 500 in second gear.....way too low...

After people's views, does 3.4:1 look like a good RMP profile....I've never had a big block so want to make sure it will have some manners on the street

Thanks in advance
Chris

[Fastbowtie]

Why don't you ditch the 400 and get a TKO 600?

You could still run the 3.40 and it would be even lower.

With a 3.40 gear set:

1st 2.87 = 9.75
5th .64 = 2.17