Cam

What ratio diff would be best suited to run with a T56 gearbox with the following ratios?
I have calculated the road speed in gear for five alternate crown wheel and pinions @ peak power
Engine spec is decatted LS9 so approx 650-700bhp with 600+ftlb from 2500rpm to redline


3.55
1st Gear Ratio 2.97:1 48.1mph
2nd Gear Ratio 2.07:1 69.0mph
3rd Gear Ratio 1.43:1 99.9mph
4th Gear Ratio 1.00:1 142.9mph
5th Gear Ratio 0.71:1 201.3mph
6th Gear Ratio 0.57:1 250.7mph
3.77
1st Gear Ratio 2.97:1 45.3mph
2nd Gear Ratio 2.07:1 65.0mph
3rd Gear Ratio 1.43:1 94.1mph
4th Gear Ratio 1.00:1 137.1mph
5th Gear Ratio 0.71:1 193.1mph
6th Gear Ratio 0.57:1 240.5mph
3.9
1st Gear Ratio 2.97:1 43.8mph
2nd Gear Ratio 2.07:1 62.8mph
3rd Gear Ratio 1.43:1 91.0mph
4th Gear Ratio 1.00:1 130.1mph
5th Gear Ratio 0.71:1 183.2mph
6th Gear Ratio 0.57:1 228.2mph
4.1
1st Gear Ratio 2.97:1 41.7mph
2nd Gear Ratio 2.07:1 59.8mph
3rd Gear Ratio 1.43:1 86.5mph
4th Gear Ratio 1.00:1 123.7mph
5th Gear Ratio 0.71:1 174.3mph
6th Gear Ratio 0.57:1 217.1mph
4.4
1st Gear Ratio 2.97:1 38.8mph
2nd Gear Ratio 2.07:1 55.7mph
3rd Gear Ratio 1.43:1 80.6mph
4th Gear Ratio 1.00:1 115.3mph
5th Gear Ratio 0.71:1 162.4mph
6th Gear Ratio 0.57:1 202.3mph

cossie4i+

iTrader: (15)

Ratios dont look very good in the box

Steve

RWD_cossie_wil

iTrader: (9)

what do you want acceleration or top end? what car is it going in? do you want 6th as a really low revving cruise gear or as another gear the engine will pull? I would say anything under 3.9 will be useless, 3.9 will be a long geared car, and you will prob end up going for the 4.4, or the 4.1 at a push.

Cam

Box is from Z06 Corvette C6 which as std runs a 3.3ratio. The 3.5 appeals as it means just 2 changes to clock a ton and leaves 6th as a proper overdrive. On paper the 4.1 looks optimal but as it is so much shorter than std gearing I am concerned it will be uncontrolable.

RWD_cossie_wil

iTrader: (9)

what car is it going into?

Cam

Grp 4 tarmac spec Chevette.

cossie4i+

iTrader: (15)

What sort of top speed will you need ?

Just pick the diff that best suits your top speed in fourth, the engine has more than enough power and torque to still make very very driveable

Steve.

Cam

I'd love to join the 200 club but 200mph in 4th would require a 2.something diff. Im thinking either a 4.1 or a 3.55 but wanted some opinions before ordering the cwp.

Mark Shead

I would look at the lower gears and cornering speed, With a quick look I would use either a 3.9 or a 4.1.

Mark

markk

iTrader: (2)

1st gear will be seam useless with that engine on anything above 3.9, so choose from there onwards, the large V8's tend to use th elow gears due to torque