The Difference of Differentials

[christyles]

Let's talk about diffs here...

[christyles]

So Eric, explain to me. I know nothing about diffs and flywheels and pretty mcuh anything to do with manual/standard car mods.

Why do you want my 3.15 diff if I had one?

[M333ee]

Well.....

A 330 5sp comes with a 2.98 diff.
If you go to a higher numerical ratio diff, you will effectively get more torque to the ground at a lower RPM. Think of it like the gears of a 10sp bike. High gears you have to pedal faster to get more speed. Lower gears you pedal much less but you get greater acceleration because the gear ratio between the input speed and the output speed is more.

You do have to weigh the pros and cons though. Higher ration means higher revs on the HWY which means more gas used...The newfound thrust will also make you a stoplight freak!

A 6sp 330 I have read on E46Fanatics can go up to a 3.44 WOW
Us lowly 5sp 330 should go up to a 3.15 at the most for OK highway revs. Anything higher and you'll be driving along at 120kph with 4-5000rpm's showing.

Someone please correct any mistakes that I've posted...

[christyles]

Well.....

A 330 5sp comes with a 2.98 diff.
If you go to a higher numerical ratio diff, you will effectively get more torque to the ground at a lower RPM. Think of it like the gears of a 10sp bike. High gears you have to pedal faster to get more speed. Lower gears you pedal much less but you get greater acceleration because the gear ratio between the input speed and the output speed is more.

You do have to weigh the pros and cons though. Higher ration means higher revs on the HWY which means more gas used...The newfound thrust will also make you a stoplight freak!

A 6sp 330 I have read on E46Fanatics can go up to a 3.44 WOW
Us lowly 5sp 330 should go up to a 3.15 at the most for OK highway revs. Anything higher and you'll be driving along at 120kph with 4-5000rpm's showing.

Someone please correct any mistakes that I've posted...
So if I did have a 3.15 on my car, why would I want to go even slower than before? :confused:
I'm trying to make my car faster. I don't know what I have, I'll find out from Cross today. but I'm defintely not making my car slower.

[M333ee]

No, the higher the number the better to a certain extent.
I have a 2.98 and I want to get a 3.15. Better acceleration off the line.
You might have a 3.15 and if you want to get faster off the line you get a higher ratio like a 3.44 :eek:

[Quickid]

Well.....

A 330 5sp comes with a 2.98 diff.
If you go to a higher numerical ratio diff, you will effectively get more torque to the ground at a lower RPM. Think of it like the gears of a 10sp bike. High gears you have to pedal faster to get more speed. Lower gears you pedal much less but you get greater acceleration because the gear ratio between the input speed and the output speed is more.

You do have to weigh the pros and cons though. Higher ration means higher revs on the HWY which means more gas used...The newfound thrust will also make you a stoplight freak!

A 6sp 330 I have read on E46Fanatics can go up to a 3.44 WOW
Us lowly 5sp 330 should go up to a 3.15 at the most for OK highway revs. Anything higher and you'll be driving along at 120kph with 4-5000rpm's showing.

Someone please correct any mistakes that I've posted...

Let's talk about diffs here...
The numbers associated with the diff means the number of drive shaft turns per turn of the axle. My 3.38 diff means the drive shaft turns 3.38 times for each turn of the axle while my old 3.07 diff means 3.07 drive shaft turns per 1 turn of the axle.

Minor correction on the bike example.... Don't confuse the momentum building phase versus the cruising phase of driving your car or your bike. It's the momentum build up that's primarily affected by having a shorter geared diff. On a bike, it's easier on your legs to build momentum when you start with the biggest rear sprocket (more pedal turns per each turn of the wheel). You eventually shift to use the smaller sprocket once you're cruising.

Similar to the bike example, you basically allow your engine to wind up quickly and bring your car to the higher rpms with a shorter diff. If you look at torque curves, they are plentiful at the higher rpm range and since a shorter diff gets you there quickly, you now have access to plenty of pulling power at a shorter elapsed time. So the secondary effect is that your engine now revs at or within the optimum power band. When you're cruising, in most cases there's no need to down shift. In some cases, you only need to downshift once.

Note that a diff swap doesn't make your car produce any more torque. You are not modding the engine, only the drivetrain. It simply lets you tap the available torque your engine already produce.

For intro on how diffs work, check out... http://auto.howstuffworks.com/differential.htm

[M333ee]

Yeh,

Quickid is correct. No extra power is gained like pullies or intake or exhaust mods. It is just that the power that is available to you is generated much more quickly.

I have heard and read that diff swaps are the most bang for the buck mods to do for acceleration.

[christyles]

Yeh,

Quickid is correct. No extra power is gained like pullies or intake or exhaust mods. It is just that the power that is available to you is generated much more quickly.

I have heard and read that diff swaps are the most bang for the buck mods to do for acceleration.
So for my 323i a-matic, how much am I looking at a diff swap?
Price difference vs. that ratio thingy number...

[M333ee]

Posted by Surk

Complete list of E46 gear ratios. Includes automatic final drive ratio.

Model...........1.......2.......3.......4.......5. ......6.......reverse Final...Final.Drive
.................................................. ......................Drive...From.Automatic
323i/ci.........4.23....2.52....1.66....1.22....1...... .........4.04....3.07....3.46
325i/ci.........4.23....2.52....1.66....1.22....1...... .........4.04....3.15....3.46
328i/ci.........4.21....2.49....1.66....1.24....1...... .........3.85....2.93....3.46
330i/ci.........4.21....2.49....1.66....1.24....1...... .........3.85....2.93....3.38
330i-6sp........4.35....2.50....1.66....1.23....1...... .0.85....3.93....2.93....3.38
330i-zhp........4.35....2.50....1.66....1.23....1...... .0.85....3.93....3.07........

323cic..........4.23....2.52....1.66....1.22....1. ..............4.04....3.46....3.46
325cic..........4.23....2.52....1.66....1.22....1. ..............4.04....3.46....3.46
330cic..........4.21....2.49....1.66....1.24....1. ..............3.85....3.07....3.38
330cic.6sp......4.35....2.50....1.66....1.23....1. ......0.85....3.93....3.07....3.38

323i-touring....4.23....2.52....1.66....1.22....1...... .........4.04....3.46....3.46
325i-touring....4.23....2.52....1.66....1.22....1...... .........4.04....3.46....3.46

325xi./touring..4.21....2.49....1.66....1.24....1........ .......3.85....3.23....3.46
330xi...........4.21....2.49....1.66....1.24....1. ..............3.85....3.07....3.46
330xi.6sp.......4.35....2.50....1.66....1.23....1. ......0.85....3.93....3.07....3.46

z4.2.5..........4.23....2.52....1.66....1.22....1. ..............4.04....3.46....3.64
z4.3.0..........4.35....2.50....1.66....1.23....1. ......0.85....3.93....3.07....3.46

I always though that the numbers were 2.98 and 3.44....oh well my mistake :(

[Quickid]

So for my 323i a-matic, how much am I looking at a diff swap?
Price difference vs. that ratio thingy number...

If you have an automatic then you might be out of luck 'cause you already have a 3.46. I've never heard anything shorter that will fit the E46.

[christyles]

If you have an automatic then you might be out of luck 'cause you already have a 3.46. I've never heard anything shorter that will fit the E46.
Awwwman. But thanks for the info Quickid. :yourmyido

[M007]

Chris, try the pulley from UUC. It's a cheaper way and not that much gain. ;)

[Surk]

Chris, try the pulley from UUC. It's a cheaper way and not that much gain. ;)

I did the Rogue pulleys...and :thumbsdow not that much noticed gain for $250 CDN from Tunerworks... It would be last on my list again...MarkD software or Shark is best bang $ >> if you can't do a diff swap..

[Quickid]

Awwwman. But thanks for the info Quickid. :yourmyido

I did the Rogue pulleys...and not that much noticed gain for $250 CDN from Tunerworks... It would be last on my list again...MarkD software or Shark is best bang $ >> if you can't do a diff swap..

Chris, There are other options like software mods as Surk01 said.... 323s and 328s benefit quite a bit from software mods. I'm still undecided which one to go for but I'm leaning towards the Shark mainly for scheduling reasons (I can install it anytime in my garage). It's definitely the next perf mod on my list.

[Canuck328i]

Posted by Surk

Complete list of E46 gear ratios. Includes automatic final drive ratio.

Model...........1.......2.......3.......4.......5. ......6.......reverse Final...Final.Drive
.................................................. ......................Drive...From.Automatic
323i/ci.........4.23....2.52....1.66....1.22....1...... .........4.04....3.07....3.46
325i/ci.........4.23....2.52....1.66....1.22....1...... .........4.04....3.15....3.46
328i/ci.........4.21....2.49....1.66....1.24....1...... .........3.85....2.93....3.46
330i/ci.........4.21....2.49....1.66....1.24....1...... .........3.85....2.93....3.38
330i-6sp........4.35....2.50....1.66....1.23....1...... .0.85....3.93....2.93....3.38
330i-zhp........4.35....2.50....1.66....1.23....1...... .0.85....3.93....3.07........

323cic..........4.23....2.52....1.66....1.22....1. ..............4.04....3.46....3.46
325cic..........4.23....2.52....1.66....1.22....1. ..............4.04....3.46....3.46
330cic..........4.21....2.49....1.66....1.24....1. ..............3.85....3.07....3.38
330cic.6sp......4.35....2.50....1.66....1.23....1. ......0.85....3.93....3.07....3.38

323i-touring....4.23....2.52....1.66....1.22....1...... .........4.04....3.46....3.46
325i-touring....4.23....2.52....1.66....1.22....1...... .........4.04....3.46....3.46

325xi./touring..4.21....2.49....1.66....1.24....1........ .......3.85....3.23....3.46
330xi...........4.21....2.49....1.66....1.24....1. ..............3.85....3.07....3.46
330xi.6sp.......4.35....2.50....1.66....1.23....1. ......0.85....3.93....3.07....3.46

z4.2.5..........4.23....2.52....1.66....1.22....1. ..............4.04....3.46....3.64
z4.3.0..........4.35....2.50....1.66....1.23....1. ......0.85....3.93....3.07....3.46

I always though that the numbers were 2.98 and 3.44....oh well my mistake :(

Eric dude...add into this list - my 328ia is a 3.07 stock. I guess that's what you get with the sport pkg. Always thought the RPM was higher than others that we test drove. This stuff is in the ETK discs too.

Hey...my first post...yet another virgin is deflowered... :)

Mark

[M007]

I did the Rogue pulleys...and :thumbsdow not that much noticed gain for $250 CDN from Tunerworks... It would be last on my list again...MarkD software or Shark is best bang $ >> if you can't do a diff swap..I haven't tried the pully yet but it is the cheapest. I talked to Mark and it seem like the software is much worth doing for 320, 323,325,328. He's charging $500 to $600 buck now.
I would have to say the next cheapest is the LFW. But it's no good for auto tranny. :)

[M333ee]

Eric dude...add into this list - my 328ia is a 3.07 stock. I guess that's what you get with the sport pkg. Always thought the RPM was higher than others that we test drove. This stuff is in the ETK discs too.

Hey...my first post...yet another virgin is deflowered... :)

Mark

He he....
Mark is alive on E46Toronto.CA :thumbsup:

Keep an eye out for a 3.15 for me. ;)

[Quickid]

I haven't tried the pully yet but it is the cheapest. I talked to Mark and it seem like the software is much worth doing for 320, 323,325,328. He's charging $500 to $600 buck now.
I would have to say the next cheapest is the LFW. But it's no good for auto tranny. :)
How much did the flywheel mod cost you altogether? Did you reuse the stock clutch kit? How much is the labour?