Diff gears! 3.7's or 3.9's?

[M01ST]

Just ring around well known wreckers and try find a hsv diff

[PedroWilsoni]

I run a VY SS series 1 auto with factory diff and just had an OTR Induction system fitted, MAF-less tune, gear-shift re-map and dyno tune, total $1400. It now pulls 461hp at the flywheel and compared to the previous dyno (plus driving it) now has bucket loads of power in the lower range. The lower range gutlessness was a real issue, but is now history. It is zippy and responsive as!

The next thing on the list for me are valve springs and diff, but if you don't already have an OTR Induction system and a MAF-less tune, etc you really should invest, it will give you a massive power increase.

[B1n0ry]

That being said ... If I went 3.9's or 4.11s would I lose alot of power mid-high revs?
Meaning quick take off, but gutless up high? Still liking the idea of 3.7s, seems like a good mediocre

No-one seemed to address this question of yours. The diff in no way affects what power the engine makes at certain RPMs. All it changes is what RPM the engine does at a certain road speed (for a given gear).
You have established that you have 3.08 at the moment. Drive at a constant speed in top gear, like 100 or 110kph and note what RPM the engine sits at. It is easy to calculate what RPM the engine will sit at with the new diff, just divide the RPM by 3.08, then multiply by 3.73, or 3.91, or whatever value you happen to be looking at.
For example, say you notice that 100kph in top gear is turning the engine at 1700RPM. with a 3.91 diff, this will become 1700/3.08*3.91, which is 2158.
Then you just have to consider whether the extra fuel usage and noise is worth the trade-off of the increased get-up off the line.

[Cameron P]

Manual s packs are standard with a 3.08 diff. If the LSD option was purchased when new then it will have 3.46 gears I believe

I have a 3.08 diff too, takes so long for first to get going lol but second and third just power on!!

[vysute]

I've got 3.9's in my SS, i tend to drag the gears a bit tho, 240kms to the tank at best city driving, 400 highway, thats babying it. but in saying that i do enjoy the 3.9's down low and wouldn't change them down. I do notice a lack of power up around 80kms-100kms on the freeway the pickup in 5th is quite lacking.

[HERONVY]

bit of an update guys, have to sell the gears now as they were out of a maloo and will not fit in my standard housing-apparently

So i got onto a complete 3.9 LSD set for 950 delivered, dad n i are going to do the conversion next week

Cant wait to see what it feels like

Al

[HERONVY]

No-one seemed to address this question of yours. The diff in no way affects what power the engine makes at certain RPMs. All it changes is what RPM the engine does at a certain road speed (for a given gear).
You have established that you have 3.08 at the moment. Drive at a constant speed in top gear, like 100 or 110kph and note what RPM the engine sits at. It is easy to calculate what RPM the engine will sit at with the new diff, just divide the RPM by 3.08, then multiply by 3.73, or 3.91, or whatever value you happen to be looking at.
For example, say you notice that 100kph in top gear is turning the engine at 1700RPM. with a 3.91 diff, this will become 1700/3.08*3.91, which is 2158.
Then you just have to consider whether the extra fuel usage and noise is worth the trade-off of the increased get-up off the line.

Thankyou for answering my question mate

I'll have a look and see what it sits on at 100kph in 5th tomorrow

All i know is that the 3.08 ratio is way too small for it atm, with the cam it seems to want to rev higher, but the diff isnt letting it do it and tends to jerk at certain speeds in certain gears, where as it didnt before

see how she goes with 3.9's

Al

[HERONVY]

I've got 3.9's in my SS, i tend to drag the gears a bit tho, 240kms to the tank at best city driving, 400 highway, thats babying it. but in saying that i do enjoy the 3.9's down low and wouldn't change them down. I do notice a lack of power up around 80kms-100kms on the freeway the pickup in 5th is quite lacking.

240??? ouch man that sucks, bet the servos are loving you! lol

In all seriousness though, must be good fun yeah? Having a mentally quick SS thats quick on the street!

Al