Choice of diff gears for starters?

[.Holdon.]

hey,
i have a VT SS 5L. what would be a good choice of diff gears to start with - 3.7's or 3.9's? have heard 3.55's dont really make too much of a difference. 3.7's seam to be the way to go but would 3.9's to too short for starters?

what have you guys with some knowledge on this found is the best set up? or advantages of each set of gears?

cheers

[fabz]

Depends what your aim is. Drags - 4.11 hiway - 3.46 (i think). happy medium would be 3.7's but all depends what your looking for. SS should have 3:46 i think already.

[immortality]

VT 5Ltr should have 3.08 ratio diff, VT s2 was the change over model with 5.7 LS1 got 3.46 (man) and 3.07(auto) a. diff gears are also influenced by the trans. 3.9's make 1st gear on a 5speed manual very short. but aren't bad with a auto trans. if you do a lot of highway driving and gas mileage is important then 3.45 are ideal

[.Holdon.]

i have an auto with 3.08 gears. dont do alot of highway driving. living in darwin atm so its mainly just driving around there. not over 100 much of the time. after the new gears to wake the car up a bit.

you said it would go thru first quickly on a manual, how would the 3.9s go in an auto?

[walesy]

the auto will be fine... im looking for a set of 3.9s for mine too...

[.Holdon.]

anyone know what rpms the 3.9's sit at when crusing at around 60, 80 or 100km/h?

[crazybiker]

It all depends on the rolling circumference of your tyres though.

[Morton]

3.89s should sit you up around 2400rpm.

My 3.73s had me on 2300rpm at 100.

[crazybiker]

On my tyres, which have a rolling circumference of 201cm, I'd be sitting on JUST over 2,200RPM to keep 100km/h, that's in 5th gear.

With the original 3.08 diff though, to sit on the same speed, in the same gear, I'd be running at around 1,850RPM.

[LAPD-VN]

a nice set of 3:45's is the way to go, mayve 3:7's but you dont want to much more unless your made of money and love to pay expensive petrol bills.

[padrickz88]

i know my car isn't a vt ss but 3.9's with an auto are fantastic i dont get much worse economy on the freeway anyway and i mainly drive around suburban/city area's so it actually helped my fuel economy.....

generally the rule of thumb is
auto: 3.7-3.9's......
manual: 3.45-3.7's..

but if you have an auto and rarely drive on the freeway then might aswell go overkill and get 4.11's.... will feel quicker off the line and fuel economy should get better

[greenfoam]

I'm very happy with 3.45s no really gain in pace over 3.08s but that's only because I don't have the other bits in it yet to suit the gears cam/manual box but everything is there to suit a long term goal

[Wagon_Wheel]

Ive got 3.9s in my clubby at the moment, 1st gear is pretty short and you notice your changing gears a lot more than you would normally. When my LSD craps it self ill prob go with 3.7s if i can find a set or just stick with the 3.9s again.
With the 5sp behind it i sit at roughly 2400rpm at 100kmh

[greenfoam]

Once you get some boost in that thing 3.45s will be perfect even 3.08s if you get enough in it

[Wagon_Wheel]

Yeah im going to judge what its like with boost, and then build a new diff with full or mini spool with some 3.45s are so if the gears are too short

[v8_stato]

i wanna get 3.9s in my stato auto sometie soon.is $550 fitted from raceshift a good price??

[Wagon_Wheel]

Depends what the $550 includes?
Are they supplying the gears or are you? Obviously those will be second hand gears.
Are they replacing bearings? Does it include diff oil? If so, is it decent oil?
Are you dropping the diff off to them or dropping the car off to them and they do it all and then putting the diff back in your car?

[VZHSV]

Ive got 3.9s in my clubby at the moment, 1st gear is pretty short and you notice your changing gears a lot more than you would normally. When my LSD craps it self ill prob go with 3.7s if i can find a set or just stick with the 3.9s again.
With the 5sp behind it i sit at roughly 2400rpm at 100kmh

hey wagz wats the fuel consumption avg when on the highway at 2400rpm

standard is like what 9-12litres per 100

[Morton]

Depending on the car, you'd be looking at 12l/100 at 100kph.

[Wagon_Wheel]

Not 100% sure, still gotta adjust my speedo lol, been too lazy. But honestly i dont use any more fuel with the 3.9s than i did with the 3.08s, but i do mainly local driving around town, not HEAPS of freeway

[VZHSV]

i want 3.7's badddd! 3.08's suck ass . slugish

[padrickz88]

Not 100% sure, still gotta adjust my speedo lol, been too lazy. But honestly i dont use any more fuel with the 3.9s than i did with the 3.08s, but i do mainly local driving around town, not HEAPS of freeway

im the same, to lazy to change it.....

BUT i was driving about 50/50 and i got over 400 to a tank of gas which is pretty damn good considering i was giving it a lil bit more then average at every lights MWAHAHAHA!

[caspa]

i got 3'9's stage 2 shift kit, trans cooler and 2,500 stally in the manta and my fuel consumption is pretty close to the same... but saying that when i go to get the cam everything will change.. stage 2 with 3'9's makes shifting from 1st to 2nd with the over rev button on heaps more fun! umm my speedo is out between 25 - 40 kms does anyone know where to get the speedo fixed and a rough price? Thanks

[Wagon_Wheel]

i got 3'9's stage 2 shift kit, trans cooler and 2,500 stally in the manta and my fuel consumption is pretty close to the same... but saying that when i go to get the cam everything will change.. stage 2 with 3'9's makes shifting from 1st to 2nd with the over rev button on heaps more fun! umm my speedo is out between 25 - 40 kms does anyone know where to get the speedo fixed and a rough price? Thanks

You can buy the speedo corrector kit from Jaycar for $50, and build it yourself and put it in, unless your not sure how to, maybe go see an auto elec.
Theres a few down your way too, BJP for one

[caspa]

thanks man