diff gears v rwkw

[HSV590]

Hey guys, dumb question time!! I was curious if anyone knows if changing diff ratios has an effect on the rwkw output on a dyno...eg..say 225rwkw with standard (cv8) diff, then same car, same dyno but with 3.9 gears fitted..would that result in a higher or lower reading, or would there be no change at all...

Cheers
Mark

[JET-33]

your rwkw will stay the same but you will notice better acceleration the higher you go in diff gear ratio

the trade off is top end speed but unless your going to the utah sand flats you will be ok :)

[damo03]

Hey guys, dumb question time!! I was curious if anyone knows if changing diff ratios has an effect on the rwkw output on a dyno...eg..say 225rwkw with standard (cv8) diff, then same car, same dyno but with 3.9 gears fitted..would that result in a higher or lower reading, or would there be no change at all...

Cheers
Mark

There will be no change at all to power output (kW). There will be a change in Torque (Nm). If you gear the car down...i.e change the diff ratio to a higher number, e.g 3.5 to 3.9 diff gears then there will be an increase in torque. It is proportional to the rpm in that gear. E.g. Changing your diff ratio by 20% will change your torque by 20%. The higher the diff ratio (number) the more torque you will have. If you go from a 2:1 diff to a 4:1 diff you will double the torque at the wheels.

The torque is also different in each gear (due to the torque multiplication effect described above) but power will be the same in every gear.

Only engine modifications (or removing losses in the driveline) will increase your power reading at the wheels.

[HSV590]

There will be no change at all to power output (kW). There will be a change in Torque (Nm). If you gear the car down...i.e change the diff ratio to a higher number, e.g 3.5 to 3.9 diff gears then there will be an increase in torque. It is proportional to the rpm in that gear. E.g. Changing your diff ratio by 20% will change your torque by 20%. The higher the diff ratio (number) the more torque you will have. If you go from a 2:1 diff to a 4:1 diff you will double the torque at the wheels.

The torque is also different in each gear (due to the torque multiplication effect described above) but power will be the same in every gear.

Only engine modifications (or removing losses in the driveline) will increase your power reading at the wheels.

Makes sense, cheers for that...

[JET-33]

has anyone ever bothered with a dyno run after doing just diff gears (3.9s in particular)?

id like to see the jump in torque

[chillicatqld]

no DIFF-erence.... :) But more enjoyable!

[LS1-5.7]

Make sure you get your speedo recalibrated if you change the factory diff ratio. :)

[HSV Listy]

Good question and I have wondered the same thing.
Have to agree with the torque difference.
Seat in the pants difference is quite noticable in diff changes. Better acceleration from lower revs and lower reves for cuising around. I think 3rd and 4th make the most difference when you put your boot into it. I only went from 3.9 to 4.1 and I class it as quite noticable.
1st and second not much but 3 and 4 yes. 5th gear I ahve not had a change to rev it up as yet. Just love cruising around in 1000 rpm to 1500. Easy skip gears from 1 to 3 and then into 5 or 6th. Only in the 60 zones I find the reves need to go above 1500. I dont accelerate at the low reves as it is not good for gear boxes but the car will put along at 1000rpm in 5 and 6th no problems. Darwin is flat too btw. Anything above 2000 these days seems to be gunning it. Putting around on low rpm and lpg good for fuel ecomony too.