Diff gears....

[gib2424]

have just recently changed from 3.08 to 3.73 in my VN V6 auto , should have done it a long time ago , although the off the mark acceleration is better I was expecting more , accelerating while moving is excellent and the revs are much lower which means the engine isn't revving itself to death like with the 3.08 , fuel economy is much better around the suburb as the vehicle moves much easier especially up hills , so anyone thinking of throwing out the 3.08 for the 3.73 go right ahead , at some stage I will go highway driving to test it out but for now still running in the new gears . happy driving everyone .

 

[Bigfella237]

have just recently changed from 3.08 to 3.73 in my VN V6 auto ~ accelerating while moving is excellent and the revs are much lower which means the engine isn't revving itself to death like with the 3.08

Is that a typo, I think you must mean you changed from 3.08 to 2.73 ???

Lowering the ratio from 3.08 to 3.73 would mean the engine would be revving much higher at the same speed.

 

[Bigfella237]

Running some quick calculations, based on the OP's tyre size and sixth gear ratio (with the torque convertor locked up), at 100km/h...

Tyre Size = 245/45R18
Tyre Revolutions = 469 per km
Gear Ratio = 0.67:1
Diff Ratio 2.92:1 = 1529 RPM @ 100km/h
Diff Ratio 3.08:1 = 1613 RPM @ 100km/h
Diff Ratio 3.25:1 = 1702 RPM @ 100km/h
Diff Ratio 3.45:1 = 1807 RPM @ 100km/h
Diff Ratio 3.73:1 = 1953 RPM @ 100km/h
Diff Ratio 3.90:1 = 2042 RPM @ 100km/h
Diff Ratio 4.11:1 = 2152 RPM @ 100km/h

...and at 160km/h...

Tyre Size = 245/45R18
Tyre Revolutions = 469 per km
Gear Ratio = 0.67:1
Diff Ratio 2.92:1 = 2447 RPM @ 160km/h
Diff Ratio 3.08:1 = 2581 RPM @ 160km/h
Diff Ratio 3.25:1 = 2723 RPM @ 160km/h
Diff Ratio 3.45:1 = 2891 RPM @ 160km/h
Diff Ratio 3.73:1 = 3126 RPM @ 160km/h
Diff Ratio 3.90:1 = 3268 RPM @ 160km/h
Diff Ratio 4.11:1 = 3444 RPM @ 160km/h

 

[UjisCaprice]

Hey all, in the process of finding a new diff for my Caprice. I only plan on OTR, exhuast and tune so do i replace it with another 2.92 but with LSD or find a 3.27 out of a HSV? Its a daily driver and its mainly used on the hwy.

 

[ducker85]

Its a daily driver and its mainly used on the hwy.

Probably the 2.92 to keep the revs down on the highway.

 

[UjisCaprice]

Thanks for that input. Are the auto transmission ratios the same between hsv and non hsv. Just thinking if a Grange comes with a 3.27 and the auto transmission ratios are the same as mine I could just put the same hsv ratio diff into mine, get the speedo corrected and bingo bango....

 

[ozNick]

Thanks for that input. Are the auto transmission ratios the same between hsv and non hsv. Just thinking if a Grange comes with a 3.27 and the auto transmission ratios are the same as mine I could just put the same hsv ratio diff into mine, get the speedo corrected and bingo bango....

It will only going to add ~10% to the revs.
There is no need to get the speedo corrected as it is taken off the wheel sensors.

 

[ducker85]

Are the auto transmission ratios the same between hsv and non hsv.

No, Holden gearboxes have different ratios to HSVs. The HSV gear are closer to make then feel more 'sporty' not sure about overdrive ratios however.

 

[Bigfella237]

I'd go with the 3.27 myself (actually I'd go lower still myself), there's more than enough legs in a six speed overdrive trans, as above, you'll only go up about 300rpm at 100km/h, it will feel a lot more lively leaving the lights and you may even be surprised by the fuel economy.

I don't have info on auto trans ratios but with the six speed manuals, the SS box has a slightly taller overdrive than the HSV, because as ducker said, HSV ratios are closer together.

 

[ozNick]

Thanks for that input. Are the auto transmission ratios the same between hsv and non hsv.

Yes - auto trans - same ratios