advice on changing diff ratios on my vt ss II 5.7lt

[james0681]

need advice on changing diff ratios on my vt ss II 5.7lt
am getting my diff rebuilt and would like to change the ratios while this is getting done
has the stock ratios at the moment but would like more power from stand still till - 100k's without comprimising to much top speed.
havn't done any other mod's yet but will be starting off with diff, then OTRCAI, extractors with 3" stainless thru out with hi-flo cats.
then eventually head and cam work!
so not sure on were to start with ratios. from wot i know these r the options i have:
3.46's
3.73's
3.91's
4.11's

also it is an auto so will be gettin stage 2 shift kit aswell

all recomendations welcome!!!

also was thinking of going to supatrik in dandenong, melbourne.
anyone been or know if they r any good? or other diff places in south-east melbourne?

 

[Claudy]

I got 4.11's and its great but mines manual so for auto id go 3.7's or 3.9's. Also when u put it in ull have to get your computer recalibrated so that your speedo isnt out

 

[james0681]

thanks 4 the quick reply claudy! probably will go 4 3.9's as it doesn't change the rev's at 100km's by that much. around 2100 rpm's i think over 1800 rpm's for stock! would they do speedo there or have to goto holden?

 

[Nanos]

i have auto ls1. i fitted few months back 3.7's. @ 100km/h sits on around 2,200 rpm. maybe bit under. I find its ok for highway. does use bit more juice on the highway though. If you dont do much highway i would go 3.9's but if you do alot of highway stick with the 3.7's. at 110km/h the revs get up around 2500 so with 3.9's at 110 would drink a lot of petrol.

also if you dont get your car retuned to suit new gears will drink a hell of alot of fuel as you need to raise the point of lean cruise. noticed massive difference in mine was i got back to my tuner and made adjustments.

dont forget to allow for a tuner to change your speedo settings.

If you have not got a new auto and have high km's i would allow down the track to rebuild it. 3rd and forth gear clutches and bands in those auto's are crap and since you will be using them alot more it wont last too long.

 

[james0681]

cheers for the responses guys. will be getting 3.9's installed after your helpfull coments!

 

[QldKev]

Still not sure if you have auto or a manual? It does make a diff :bow:

Myself to allow some country work
Auto 3.7
Manual 3.9

If your never going to go country
Auto 3.9
Manual 4.11

Then you'll be :w00t:

QldKev

 

[VT_Cruiser]

I also have a std diff in the same car type and was wondering what difference you could expect changing from a std diff to the 3.7 for example in a auto. I know its relative to engine power and everything else associated with your own car, but would the extra fuel cost, build cost etc amount to much in terms of time? maybe 1/2 a second? just curious.

 

[Vt_vic]

acceleration is a lot better im gonna get 3.7 as 3.9's srent really good for highway as you revving around 2500 while the 3.7 is just over 2000