Changing Diff Ratio?

[Jack_Keaka]

Has anyone or does anyone know if you change the the differentials for better highway RPM?
currently in my 5sp it sits at 3k at 100kph. 3100-3200ish at 110. this is just too high and eats through too much petrol. has anyone changed this?
id be happy to even just loose 1-200 rpm.
any other (serious) solutions?
from my understanding Liberty ratios are taller than rex's? so is there anything even taller? or am i misinformed..

[Mat04]

I think you would have to change your gearbox also mate as I think they are matched ratios ie auto rear diff is different ratio to manual rear diff.

[Jack_Keaka]

so i can't just swap the diff? excuse my noobness on this topic but when i try to search, its all gay commodores or WRX's changing to the Liberty 6sp box & diff (which i think aren't much better than a 5sp anyway)

[Mat04]

Not from my understanding you won't be able to. Best bet would be speak to Michael or anyone else that you could get an answer out of.

[Jack_Keaka]

yeah ill probably have a chat to michael next time im at G88. i just always forget haha
thanks

[mynameisdaniel]

You could put bigger wheels/tyres on... Won't make a massive difference though...

[Jack_Keaka]

You could put bigger wheels/tyres on... Won't make a massive difference though...

[coyote]

The simple answer is "don't". You'll spend more on the conversion than you'll save on petrol over the next 20 years. Just get higher profile tyres if it really bothers you THAT much.

Long answer is that you probably* have a 4.1 final drive and could probably* swap it for a 3.9. I went the other way many (MANY) years ago and swapped a 3.9 to a 4.4. Car did 3200rpm at 100km/h and I actually hit the rev limiter in top gear on some tracks.

* I'm probably talking out of my arse with complete guesses.

[zch91]

Mine does about 2.2k at 100, and around 2.5 at 110

[Jack_Keaka]

The simple answer is "don't". You'll spend more on the conversion than you'll save on petrol over the next 20 years. Just get higher profile tyres if it really bothers you THAT much.

Long answer is that you probably* have a 4.1 final drive and could probably* swap it for a 3.9. I went the other way many (MANY) years ago and swapped a 3.9 to a 4.4. Car did 3200rpm at 100km/h and I actually hit the rev limiter in top gear on some tracks.

* I'm probably talking out of my arse with complete guesses.

its just after i drive my brothers ford ute which sits at 1500rpm at 100 and still has a bit of push, and then get in mine and its revving its bum off at 100 just makes me depressed. but it wouldn't really be about saving money but more a sense of having a nice quiet car on the highways that doesn't eat through petrol like theres no tomorrow.

Mine does about 2.2k at 100, and around 2.5 at 110

are you an auto driver though? as you'd have overdrive where as i have 'putting my foot on the clutch down hills'

[zch91]

Yeah 5 sp tiptronic

[Jack_Keaka]

yeah I'm not going the automatic road just yet

[dawesy]

Yeh as stated would need to change gearbox and rear diff.
Easiest as stated run a set of 18s on bigger profile tyre might knock 1-200 rpm off if youre lucky

[coyote]

No need to change the gearbox, just both diffs.

Hopefully by now Jack has realised this is not a good idea.

[Jack_Keaka]

I knew it wasn't going to be a fun idea, just wanted to know how much fun it is exactly.
Checked this morning and it sits at 2900 exactly. Maybe I'll buy some 18's and see what it does...
Or buy a better car