4.1 Ratio Medium Case Gear Set.

[|ncary 0]

I understand this ratio is used for the race series, so there will be a lot of parts hoarding by the competitors ha.. Fair enough.

I'm only after the actual gear set so I can bolt my Limited Slip unit inside it. It's exactly what my car needs..

Aaaaaaaand go:

[BM WORLD 1285]

marty is your man (bm weapon)

http://www.trademe.co.nz/Trade-Me-Motors/C...n-253283171.htm

[*Glenn* 855]

I understand this ratio is used for the race series, so there will be a lot of parts hoarding by the competitors ha.. Fair enough.

I'm only after the actual gear set so I can bolt my Limited Slip unit inside it. It's exactly what my car needs..

Aaaaaaaand go:

Do you mind me asking why a 4.1:1 ?? The 325 can easily handle a 3.64:1. What ratio do you have now ??

[Silver Fox 43]

I run a 4.1 LSD in the E28 and agree it's the way to go with the overdrive manual box in a race car.

The car becomes so much more responsive, and you can keep the engine in the right rev range very easily.

The race series usually run the small case diffs, so there isn't that much demand for the med case 4.1's, you can just transfer the ring and pinion to your med case from most pre 94 med case ones.

[c.robertson00 11]

I run a 4.1 LSD in the E28 and agree it's the way to go with the overdrive manual box in a race car.

The car becomes so much more responsive, and you can keep the engine in the right rev range very easily.

The race series usually run the small case diffs, so there isn't that much demand for the med case 4.1's, you can just transfer the ring and pinion to your med case from most pre 94 med case ones.

Why do most of the series guys run small case diffs? Wouldnt be better to have the large case diff in terms of the ballast that most cars carry to meet the minimum weight. Its low down and towards the rear so it should be better than adding the extra weight in the spare wheel well? And the medium case is a stronger diff aswell

[Apex 693]

Would think regs wouldn’t allow it as the E30 didn’t come with a large case factory?

[Silver Fox 43]

Why do most of the series guys run small case diffs? Wouldnt be better to have the large case diff in terms of the ballast that most cars carry to meet the minimum weight. Its low down and towards the rear so it should be better than adding the extra weight in the spare wheel well? And the medium case is a stronger diff aswell

You are right Chris, some of the cars do run with the med case, mainly the 320's, because they need the weight, the 318's don't, so they seem to stick with the small case ones. You can use either in the series, they are both 4.1 so no worries there. Because they mainly came with the small case that's the one most do use, I haven't heard of any breaking yet due to natural causes, and I know of someone putting 200 plus rwhp thru one.

[Silver Fox 43]

Would think regs wouldn’t allow it as the E30 didn’t come with a large case factory?

I've been told some SA ones came with the med case, and have broken one that had one, but of course it may have been retrofitted.

[*Glenn* 855]

I removed my "ooops" I thought you had to run the small case 4.1 only... I'll leave it to the race series experts

[c.robertson00 11]

I've been told some SA ones came with the med case, and have broken one that had one, but of course it may have been retrofitted.

Yea i've got a medium case 4.1 in my race car out of a S.A 318i

[CamB 48]

I agree - a 4.10 would help acceleration nicely. I had a 4.27 in the 2002.

[|ncary 0]

Do you mind me asking why a 4.1:1 ?? The 325 can easily handle a 3.64:1. What ratio do you have now ??

The 325i isn't really a torque monster like a turbo/4l V8, it stuggles in any gear other than 1st or 2nd to get decent acceleration.

I currently have a 3.64 and the speeds in each gear are : 86 in 2nd, 135 in 3rd and 189 in 4th (at 6250rpm), my friends turbo cars have similar in-gear speeds, which is just silly for my 220Nm or so.

3rd gear is the most used gear, and it's too long for the roads my car gets used on, never see's above 5k rpm, when it should be hitting redline..

A 4.1 will reduce those gear speeds to 76, 120, 168. Will add 2 extra shifts up to 4th gear to a lap of Ruapuna, and 2nd gear might be just slightly too short to how I'm used to it now, but the difference it makes in 3rd will make up for all of this.

And thanks Brent, Marty has PMed me

[CamB 48]

I wouldn't count on 3rd making up for it.

I found that at Taupo, where I am between 2nd and 3rd a lot, that the dirty old M10 torque made me almost as quick in 3rd despite the gear being obviously unsuitable for a couple of the corners (it was in the order of 0.5 seconds per lap slower). I consider an M20 to be pretty torquey to be honest.

Basically the shorter ratio is a band aid - what you really need is better gears (anyone got $3k plus hanging around?).

Edited November 18, 2009 by CamB

[|ncary 0]

Yes, custom ratios would be fantastic. But a 4.1 would make a huge difference. You only use 2nd gear once at Ruapuna, and 6 sections of 3rd gear where 4 of those 6 it is not really near peak power. With a 4.1, 4th could be hooked 3 times per lap, rather than once, with most of the time being spent quite high in 3rd gear. And with R-comps 3rd will be even more effective, with all corners, bar one, being 3rd gear corners, with a higher cornering speed it's going to really shoot out of the curves with the revs right up.

And don't get me started on how it'll make the Summit Rd even better to drive

We will see though. I see no harm in having a shorter ratio back there.

[e30ftw 410]

Are you sure you have a 3.64? Not a 3.46?

My 3.64 gets 95km/h 2nd, 145 3rd @ 6200rpm..

With a 4.45 it was 70ish 2nd, 115ish 3rd, 145ish 4th IIRC ?

[|ncary 0]

Of course I'm sure. I don't use the speedo to get the speeds, way too inaccaurate. My speedo indicates similar. Also I'm running slightly undersized tires at the moment (205/50/15) (At the last track day the tires were correct size however)

Bookmark it: http://members.dodo.com.au/~wawawa/revs.htm

[tibbs.james 1]

Time to tighten the LSD while its apart ?

sorry about off topic

a 4.1 sounds like the business ! can't wait to feel the difference on the 22nd

[|ncary 0]

Yes, would order new clutch packs from the states and get it increased to 40%

Not sure if I'll have it all done by the 22nd. DCH charge way too much for Diff work.. But hey we'll see!

[tibbs.james 1]

Justin Neil Lower Styx Road 03 329 8518- tell him sam or I sent you

Last week my 300zx gearbox was sharing his table with Sam's diff for his v8

he did a beautiful job with Rileys & my Gearbox , Sam is having his diff setup by him too so he can probably let you know how much it cost

He machines his own clutch pack shims to suit the diff instead of just opening a packet that cost a golden brick or two

[|ncary 0]

Why thanks James.