SD1 diff ratio 3.08 vs 3.45

[kokkolanpoika]

Hi.

I need advise and experience..

I have got SD1 5,2litre, power approx 350hp@5500rpm / 540Nm@3500rpm (last year with lean mixture 324hp@4970rpm / 520Nm@3280rpm) rev limit 6200rpm

So question is i have got LT77 D suffix and 3.08 diff ratio. 235/45-17 tyres.
So if i change diff ratio to 3.45, dos it make any difference in performance 0-100km/h times, 1/4mile times/speed??
Theoritically yes?

But now my car goes 2nd gear approx 6000rpm and 111km/h. 3rd gear approx 170km/h@6000rpm.
So i calculate if i change 3.45 ratio 2nd gear it will go @6000rpm 100km/h and 3gear 150km/h.

With my ex 4,6 engine when i drive my first 1/4mile i drive with 3rd gear and 158km/h/14,8 and lot of grip proplem.

So i think if i chane 3.45 ratio i have to change gear 1 time more at 1/4mile witch will eat time approx 0,5second? And theoritically 0-100km/time can be worse if i change gear @ 5800rpm..

I just bought APEX RSM meter. Theoritically it will go 0-100km/h 5.2second and just on 2nd gear.. Have to test 1/4mile when night comes..

http://img31.imageshack.us/img31/6772/img1545q.jpg

I usually drive in the city and 1/4mile intrest me moust, so what do you thing to change diff ratio?

[unstable load]

Try this out....

http://www.corral.net/tech/gearcalc.html
http://www.et-studios.com/motorsports/gears/gears.html