Diff Ratios?

[HarroVX]

hey guys, can anyone actually explain to me what the #### diff ratios are all about?
ive been told about them before but not in detail.

[Cameron P]

its the ration between the pinion teeth (forget the technical term) and the crown wheel teeth. if you mark one tooth on the pinion and turned it the whole way around the crown wheel you will get the ratio

someone correct me if im wrong :P

[Kernal]

Just think about it like this. The usual standard diff ratio on a commodore is 3.08 - 1
Now think of that as first gear on a mountain bike. You have to peddle hard to get it moving right??
Now put the bike in a higher gear, say 4th. Its a lot easier to get it moving yeh? you dont have to work as hard.

Now if you put a higher diff gear in your commodore (correct term is taller and shorter but its easier to understand like this), say 4.11, your car wont have to work as hard to get moving.

The gears go up in these increments; Standard is 3.08 and 3.46, upgrades are 3.73, 3.89 and 4.11. the higher you go the less your car has to work to get moving therefore you will have faster acceleration, however, the higher you go, the less your top speed will be.

Although diff gears wont affect you ET's much, it will make a difference in your 60 footers as it helps you get out of the hole.

If you mostly drive in the city/suburbs i would recommend 4.11, you wont look back. But if you do quite a bit of freeway/highway driving maybe 3.46 or 3.73. However i stll went 4.11 and havent look back.
Why? you ask. Because the higher the diff gear the more you'll be revving at freeway speeds 100kmph. But if you can put up with drone (if your exhaust system has drone), and dont mind paying $5 extra in petrol a week go 4.11, either way you wont regret it.

[Mirkz]

what's the usual cost to rebuild a diff or fit new diff gears? (I'm not sure if this is one in the same???)

[Brett_jjj]

Just think about it like this. The usual standard diff ratio on a commodore is 3.08 - 1
Now think of that as first gear on a mountain bike. You have to peddle hard to get it moving right??
Now put the bike in a higher gear, say 4th. Its a lot easier to get it moving yeh? you dont have to work as hard.

Now if you put a higher diff gear in your commodore (correct term is taller and shorter but its easier to understand like this), say 4.11, your car wont have to work as hard to get moving.

The gears go up in these increments; Standard is 3.08 and 3.46, upgrades are 3.73, 3.89 and 4.11. the higher you go the less your car has to work to get moving therefore you will have faster acceleration, however, the higher you go, the less your top speed will be.

Although diff gears wont affect you ET's much, it will make a difference in your 60 footers as it helps you get out of the hole.

If you mostly drive in the city/suburbs i would recommend 4.11, you wont look back. But if you do quite a bit of freeway/highway driving maybe 3.46 or 3.73. However i stll went 4.11 and havent look back.
Why? you ask. Because the higher the diff gear the more you'll be revving at freeway speeds 100kmph. But if you can put up with drone (if your exhaust system has drone), and dont mind paying $5 extra in petrol a week go 4.11, either way you wont regret it.

Its actually the other way around ,the lower the diff ratio,the higher the engine will rev on the highway.The 4.11 gears are actually lower than 3.08 gears,not higher.The higher the number,the lower the ratio.

[Cameron P]

wpn.. what revs are you sitting on doing 100km/h?

and what gearbox do you have?

[Mirkz]

I was always under the impression higher diff ratio, the higher revs at fwy driving...

Edit: duuh huurrrr just read the rest of the post :/

[Brett_jjj]

The higher the diff gearing is,the lower the engine will rev at highway speeds,but it also makes the car sluggish to get going off the line ,and slow to pick up speed.This is why people fit lower gears,like instead of 3.08:1 ratio,they will fit a lower ratio of 3.5:1,this makes the car way better off the line,and gives better pickup,but it will be reving harder at highway speeds with the lower diff gears fitted.

[Paul13pp]

I used to have a 2.78 diff and a commodore 5 spd box in a HR ute.
She was a real cruizer on the highway. hardly any rev's.

Can you get ratios like that for VS's?
I know the one in it is a 3.08 but it would be more ecconomical on the highway with something like a 2.78.
It is not like there is a lack of takeoff power.
I'd hate to have 4.11 ratio with the engine reving its tits off at 110 klm/h wering everything out faster and using more fuel.

[VUte89]

So do any of you know if the LSD in the vu has a different ratio to the non LSD in a vx sedan

[a1k3m1]

I used to have a 2.78 diff and a commodore 5 spd box in a HR ute.
She was a real cruizer on the highway. hardly any rev's.

Can you get ratios like that for VS's?
I know the one in it is a 3.08 but it would be more ecconomical on the highway with something like a 2.78.
It is not like there is a lack of takeoff power.
I'd hate to have 4.11 ratio with the engine reving its tits off at 110 klm/h wering everything out faster and using more fuel.

i would love to know the answer to this too! .. would it use more fuel at lower revs, or would the computer thing pump in more fuel to make up the lack of revs? .. so would you really be saving in fuel getting a 2.78 ratio? .. as i use my car mostly for highway driving, so a 4.11 ratio is kinda silly IMO.. but maybe a 2.78 or something is something to think about?

[Kernal]

what's the usual cost to rebuild a diff or fit new diff gears? (I'm not sure if this is one in the same???)

Usually between $1200 and $1500, but theres a guy on ebay thats sell reco one with LSD or Mini spool and your choice of gears for $800ish. I have done over 70000ks on it and shredded countless sets of tyres, never had a problem.

Its actually the other way around ,the lower the diff ratio,the higher the engine will rev on the highway.The 4.11 gears are actually lower than 3.08 gears,not higher.The higher the number,the lower the ratio.

Oh yeh my bad lol

wpn.. what revs are you sitting on doing 100km/h?

and what gearbox do you have?

2500 Auto 4 speed.

So do any of you know if the LSD in the vu has a different ratio to the non LSD in a vx sedan

im pretty sure utes and wagons came out with 3.46s and sedans with 3.08s

[GM GEN3]

I got 3.9.1's in my ss run's good wit them plus be m6 also helps but if I'm doing 100 the car rev's are about 1500 in 5th gear it cost me 1200 for full rebuild plus gears

[TonyJZX]

why not just chuck a $500 eaton truetrac in it?

i would think a higher ratio works well on the LS1 since 5th and 6th are practically useless

[GM GEN3]

Yeah I've had my off the clock 220 in 5th wit 6th gear to go this was on a track of course!

[HarroVX]

thanks guys, this helped heaps!
my diff is clunking real bad at the moment and i was looking at getting another diff perhaps and LSD, i have a VX Acclaim, any suggestions on a diff?
and i do a fair bit of highway driving for work, and my exhaust does drone a fair bit already, i mean i can put up with it over my subs and stuff but if it got any louder i would go nuts.
And could there be some slack on my drive shaft cause the clunk and shudding?
thanks again guys!

[Kernal]

3.46 or 3.73

[Mirkz]

Usually between $1200 and $1500, but theres a guy on ebay thats sell reco one with LSD or Mini spool and your choice of gears for $800ish. I have done over 70000ks on it and shredded countless sets of tyres, never had a problem.

I think I found the guy you were on about, didn't look too shabby.

Whats the difference between mini spool and LSD?

[Kernal]

I think I found the guy you were on about, didn't look too shabby.

Whats the difference between mini spool and LSD?

Mini spool is for the race track but ppl still use it on the street. Both wheels spin at the same rate no matter what. When you turn tight corners the inside wheel will chirp coz its spinning at the same rate as the outside wheel. Its dangerous in the wet coz the chance of getting tail happy without the intention of doing so is greatly increased.

LSD spins both wheels at the same rate but has some give in it. So no chirping around corners and the chance of unintentional sideways action is greatly reduced in the wet = safer, a lot safer. LSDs also wear out but that would take 200 000+ kms depending how much you punish it. The original one on my car lasted 210000 then i got a new one with new gears. By wear out i mean turns into a single spinner. But all you have to do is get a diff place to tighten the LSD and your ready to leave some more sick marks.

Some people say if you know how to drive mini spool you will be fine, but i wouldnt risk it. you would be stupid to.

Hope this helps

[Mirkz]

Thanks.
Think I'll go for the LSD rather than mini spool.
Will have to look into doing this next after my bumper and then seats :P
Not looking to build a track car, just a power hungry street machine