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What Diff Ratio to get?

GIMPEESS

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Hi All im just wondering if anyone could recommend what diff ratio i should put in my 5L VP irs commodore. It needs a better take off as its a little sluggish off the line. But i dont want it to be revving its tits off on the Highway. Any help would be greatley appreciated!!!!!
 

AirStrike

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Is it an auto or manual? There isn't any way really to get the best of both worlds, I have 4.11's and its an animal off the line but sits abit above 2,500rpm @ 100km/h.
Us the program I have included to work out what it will rev at for a given speed.
Use the following ratios:
auto said:
1st 3.06
2nd 1.63
3rd 1.00
4th 0.70
manual said:
1st 3.25
2nd 1.99
3rd 1.29
4th 1.00
5th 0.72
 

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V85000i

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i'm gonna get 3.7's. and i do a lot of open road driving, but i worked out that the fuel usage won't be that much worse.
 

10000_fists

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I have a V6 AUTO with 3.7 diff gears and at 100k's(123 on speedo) it revs at 2300rpm. I didn't notice a great change in fuel consuption, and it made a big difference in take off, i'd recomend 3.7 gears...
i never worked it out but i reckon my average fuel consuption probably only changed 10-20k's per tank, i can still easily get 380+ out of about 50 litres, thats with the supercharger on to, with 30-30k's everyday on the highway, rest is flogging round town.

Just note that changing your diff gears will effect you speedo reading, when my gauge says 123 i'm really doing 100km/h
 

pumba

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i have 3.9 geas in my VP SS (irs) and i sit on about 2600 rpm at 100km/h

as 10000_fists said, it will affect your speedo abit aswell. mine sits on about 130km/h when doin 100km/h... so yea, u quickly learn to read it differently lol.

and i probably get about 350kms per tank with about 50% highway and 50% city driving
 

vq~gangsta

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There have been lots of threads on this subject, just search for 'diff ratio'

I would recomment 3.45 if you're on a budget, that's what i've got. You can get the gear second hand from VL turbos, but they are a little hard to come by.

Otherwise for an extra couple of hundred dollars you can get a 3.7 ratio. It's a wider cog, so it's stronger, and it will give you a little more accelleration than the 3.45

If you want to do the car up for the drags i'd use a 4.11 if you had up to about 250 Kw, and 3.9 if you had over 250 Kw. Beware though, these ratios will completely kill your fuel economy on the open road.
 

JD

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3.45 are a nice ratio, mate just got them on his vn and it made a hell of a difference
 

AirStrike

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3.45 are a nice ratio, mate just got them on his vn and it made a hell of a difference
You would **** a brick jumping in mine with 4.11's then:p
 

Immortality

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i changed my VH (V8 trimatic) from a 2.6:1 to 3.08:1 and didn't notice a thing, except that i couldn't break every speed limit in the country in first gear any more
 
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