[6MT] Changing gearbox gears ratio or diff final drive ratio?

[jvictormp]

Hey guys.

I'm not satisfied with the gear ratio of the 6MT, I think it kills pretty much of the torque when you shift to 3rd and 4th. Actually I'd like to make 1~5 gear shorter, keeping the 6th like an overdrive gear.

I would make my street rides more fun, yeah, but mainly the track days.

I've seen some posts about shorter final drive ratio, but none about the gearbox.

Is it too expensive to do that? Change the 5 gears of the gearbox?

That would lead me to the other option, which is changing the final drive ratio.

I've been watching some videos, and the 4.10 seems to be not enough for what I expect. The 4.44 is quite that.

This is a 4.44 final drive:

Compare to my stock 3.85 final drive:

I can't help beeing amazed for the 4.44. Those gears fit so perfectly.

But fuck, the 4.44 is $2k more expensive than the 4.10. But whatever, I would pay.

6th gear will be shortened too, I know, but I can stand it, as we don't have any road here in Brazil which is allowed to travel above 75mph, and I'm not a final speed lover. But in the track I want to have all the gears in the optimum torque band.

And on the street, I want to spin the rear wheels anywhere.

Well, cut the talking.

What would be more expensive? Gearbox ou differential?

[DukeofAlexandria]

Originally Posted by jvictormp

Hey guys.

I'm not satisfied with the gear ratio of the 6MT, I think it kills pretty much of the torque when you shift to 3rd and 4th. Actually I'd like to make 1~5 gear shorter, keeping the 6th like an overdrive gear.

I would make my street rides more fun, yeah, but mainly the track days.

I've seen some posts about shorter final drive ratio, but none about the gearbox.

Is it too expensive to do that? Change the 5 gears of the gearbox?

That would lead me to the other option, which is changing the final drive ratio.

I've been watching some videos, and the 4.10 seems to be not enough for what I expect. The 4.44 is quite that.

This is a 4.44 final drive:

Compare to my stock 3.85 final drive:

I can't help beeing amazed for the 4.44. Those gears fit so perfectly.

But fuck, the 4.44 is $2k more expensive than the 4.10. But whatever, I would pay.

6th gear will be shortened too, I know, but I can stand it, as we don't have any road here in Brazil which is allowed to travel above 75mph, and I'm not a final speed lover. But in the track I want to have all the gears in the optimum torque band.

And on the street, I want to spin the rear wheels anywhere.

Well, cut the talking.

What would be more expensive? Gearbox ou differential?

Ok, ignore all that bullshit you just wrote about cost, and which is better, and can you do a gear box ratio upgrade, blah blah blah.

The real question is: have you done the math and the calculations on trans ratios vs. 4.44 gearing?

Go run rpm vs gearing calculations and do you think you can live with that?

-Duke

[jvictormp]

Originally Posted by DukeofAlexandria

Ok, ignore all that bullshit you just wrote about cost, and which is better, and can you do a gear box ratio upgrade, blah blah blah.

The real question is: have you done the math and the calculations on trans ratios vs. 4.44 gearing?

Go run rpm vs gearing calculations and do you think you can live with that?

-Duke

I'm attaching the math below.

I want the shorten the five first gears, but keep the original 6th gear ratio.

If that is more expensive, I would give up on the long 6th gear ratio, and would go with the shorter diff ratio.

I just was curious about tuning the gearbox gear ratios, and couldn't find any info about it.

[DukeofAlexandria]

Originally Posted by jvictormp

I'm attaching the math below.

I want the shorten the five first gears, but keep the original 6th gear ratio.

If that is more expensive, I would give up on the long 6th gear ratio, and would go with the shorter diff ratio.

I just was curious about tuning the gearbox gear ratios, and couldn't find any info about it.

Ok, so you've done the calculations and you want to live with those ratios, which is fine.

The gearing would be the easiest and simplest way to go. If you find someone who can rebuild your 6MT with updated/upgrades ratios, it's going to cost probably in the 7-10K range (I'm ballparking it here).

They'll have to match up ratios to your 4.44 and ensure it works and syncs up correctly to actually be usable on track or street.

Additionally, you'll need some tuning for the engine to ensure DME doesn't throw some crazy codes for engine speed vs trans speed or whatever weird stuff might come up.

Not saying it can't be done, I've just never heard of anyone doing it or read about it. Someone might have, I just don't know.

-Duke

[jvictormp]

Originally Posted by DukeofAlexandria

Ok, so you've done the calculations and you want to live with those ratios, which is fine.

The gearing would be the easiest and simplest way to go. If you find someone who can rebuild your 6MT with updated/upgrades ratios, it's going to cost probably in the 7-10K range (I'm ballparking it here).

They'll have to match up ratios to your 4.44 and ensure it works and syncs up correctly to actually be usable on track or street.

Additionally, you'll need some tuning for the engine to ensure DME doesn't throw some crazy codes for engine speed vs trans speed or whatever weird stuff might come up.

Not saying it can't be done, I've just never heard of anyone doing it or read about it. Someone might have, I just don't know.

-Duke

I may not be understanding right, or you're misunderstanding the theory.

I can either change ONLY the final drive gear, which is located in the differential, or change ONLY the gears in the gearbox. There's no need to do both.

If I choose to go by the final drive gear, I'll change the wheel speed in all the gears, which will make the 6th gear a not so good gear to drive in long trips.

If I choose to go by the gears in gearbox, I can shorten only the 1st to 5th gears, and leave the 6th stock, keeping it good to drive in long trips.
The only con would be the big RPM drop from 5th to 6th gear, but absolutely no problem with that.

[DukeofAlexandria]

Originally Posted by jvictormp

I may not be understanding right, or you're misunderstanding the theory.

I can either change ONLY the final drive gear, which is located in the differential, or change ONLY the gears in the gearbox. There's no need to do both.

If I choose to go by the final drive gear, I'll change the wheel speed in all the gears, which will make the 6th gear a not so good gear to drive in long trips.

If I choose to go by the gears in gearbox, I can shorten only the 1st to 5th gears, and leave the 6th stock, keeping it good to drive in long trips.
The only con would be the big RPM drop from 5th to 6th gear, but absolutely no problem with that.

You can do both, it just comes down to cost at that point.

4.44 gears would be cheapest. 4.44 gears + trans ratio rebuilt would be crazy expensive.

Not saying you can't do both, again, just comes down to cost.

Additionally, at that cost point, why not just get a S/C and not mess with gearing? You'll get nearly the same results, if not better from the increase in HP.

-Duke

[driftflo]

why is a 4.44 cwp $2k more expensive then a 4.10?

due to limited stock at the moment i sell the 4.44 for eur 1.200,- compared to eur 1.000,- for the 4.10. so this is only €0.2k more.

you can instead use the saved $1.8k to also fit a proper clutch lsd which improves handling and traction a lot!

i never heard of other gears available for m3 6mt gearbox. i guess this conversion would be way to expensive. no one will spend this for a street car. and if you want to spend it for a racecar it makes more sense to just swap to a sequential racing box where you can choose each gear individually when ordering.

[jvictormp]

Originally Posted by DukeofAlexandria

You can do both, it just comes down to cost at that point.

4.44 gears would be cheapest. 4.44 gears + trans ratio rebuilt would be crazy expensive.

Not saying you can't do both, again, just comes down to cost.

Additionally, at that cost point, why not just get a S/C and not mess with gearing? You'll get nearly the same results, if not better from the increase in HP.

-Duke

Let's say I go with the 4.44 final drive gear. It's a $5k buy. It's cheaper than S/C, and my engine is at this pretty moment out of the streets so I miss that reliability feeling which the S/C leads outward it even more.

S/C is not something I'm adept to.

[jvictormp]

Originally Posted by driftflo

why is a 4.44 cwp $2k more expensive then a 4.10?

due to limited stock at the moment i sell the 4.44 for eur 1.200,- compared to eur 1.000,- for the 4.10. so this is only €0.2k more.

you can instead use the saved $1.8k to also fit a proper clutch lsd which improves handling and traction a lot!

i never heard of other gears available for m3 6mt gearbox. i guess this conversion would be way to expensive. no one will spend this for a street car. and if you want to spend it for a racecar it makes more sense to just swap to a sequential racing box where you can choose each gear individually when ordering.

Now that's what I was expecting to find. Such amazing price that is!

In the internet I only found the 4.10 M-Diff for 2.5k USD, and the 4.44 M-Diff for 5k USD.

I'll keep that in mind, driftflo

Not buying it right now, but I will.

By the way, you gave me the argument that I needed about tuning the gearbox.

[driftflo]

currently i have one last 4.44 cwp in stock.
not sure when the next batch will come. bmw motorsports parts (for older cars that are no more used in competitive racing) are sometimes out of stock for long time. i heard they want to produce some new ones... but i do not know when they become available.

btw: 5k is a bad joke!

[SYT_Shadow]

Originally Posted by driftflo

i never heard of other gears available for m3 6mt gearbox. i guess this conversion would be way to expensive. no one will spend this for a street car. and if you want to spend it for a racecar it makes more sense to just swap to a sequential racing box where you can choose each gear individually when ordering.

Agreed, I have never heard of this either

[HolyChitMeng]

I just made the switch from a OE 3.85 to a Dinan 4.10 Gear set and it woke the car up.
Has enough torque down low for 3rd-4th backroad driving.
I can't imagine having gears shorter than this though.

[jvictormp]

Originally Posted by HolyChitMeng

I can't imagine having gears shorter than this though.

Thanks for sharing. Would you mind explaning a little more about this?

[HolyChitMeng]

Originally Posted by jvictormp

Thanks for sharing. Would you mind explaning a little more about this?

The car picks up revs quick.
Even around town on low speed roads you'll catch yourself in 4th and 5th rather frequently.
I understand having vanos engaged by every gear shift by adding a 4.44, but also doing custom gears just wouldn't be worth the price and the usability of the car.
For your purposes on tighter race tracks I can see why you'd want a 4.44, but it just wouldn't make sense anywhere else.
Instead of spending 10k on a transmission, you can do a stroker motor, and have the down low power you're looking for without losing the drivability of the car.
I believe Dinan paired the 4.10's with their strokers and saw great results.

[Isaiah22]

Originally Posted by HolyChitMeng

The car picks up revs quick.
Even around town on low speed roads you'll catch yourself in 4th and 5th rather frequently.
I understand having vanos engaged by every gear shift by adding a 4.44, but also doing custom gears just wouldn't be worth the price and the usability of the car.
For your purposes on tighter race tracks I can see why you'd want a 4.44, but it just wouldn't make sense anywhere else.
Instead of spending 10k on a transmission, you can do a stroker motor, and have the down low power you're looking for without losing the drivability of the car.
I believe Dinan paired the 4.10's with their strokers and saw great results.

So Im looking to get a new diff since i blew mine, and im considering changing from the 3.85. If i got a 4.10 would i accelerate to 100 faster than the 3.85? If i lined up with a car with a 3.85 would I be faster given we were both stock? is there any speed the 3.85 might be faster?

[nycplumber]

Originally Posted by Isaiah22

So Im looking to get a new diff since i blew mine, and im considering changing from the 3.85. If i got a 4.10 would i accelerate to 100 faster than the 3.85? If i lined up with a car with a 3.85 would I be faster given we were both stock? is there any speed the 3.85 might be faster?

There is a video on YT of E46s with 3.62/3.91/4.10 roll racing and as you'd expect the 4.10 was the fastest, followed by the 3.91 and then the 3.62. I remember a while back a bunch of geeks arguing the opposite but what works on an excel spreadsheet doesn't translate to real life.

[MineralWhiteF80]

insert E46 M3 diff racing video

[M3SQRD]

Originally Posted by nycplumber

There is a video on YT of E46s with 3.62/3.91/4.10 roll racing and as you'd expect the 4.10 was the fastest, followed by the 3.91 and then the 3.62. I remember a while back a bunch of geeks arguing the opposite but what works on an excel spreadsheet doesn't translate to real life.

I miss my e46 M3 with 4.10 FD

I regret selling my slick top, manually adjustable seats Imola Red/Imola Red e46 M3 with too many mods to list.

I love the 3.62 FD DCT in my e92 M3!

[nycplumber]

Originally Posted by M3SQRD

I miss my e46 M3 with 4.10 FD

I regret selling my slick top, manually adjustable seats Imola Red/Imola Red e46 M3 with too many mods to list.

I love the 3.62 FD DCT in my e92 M3!

I had an E46 with 4.10fd keep up with me when I was FBO. They are no joke and super quick for a car with a 20+ year old NA engine.

Also in this video it seems like with the new FD you are much higher in the rev range after each shift basically making more power the entire pull, negating any shift time loss

[M3SQRD]

Originally Posted by nycplumber

I had an E46 with 4.10fd keep up with me when I was FBO. They are no joke and super quick for a car with a 20+ year old NA engine.

Also in this video it seems like with the new FD you are much higher in the rev range after each shift basically making more power the entire pull, negating any shift time loss

E46 M3 w/ 4.1 FD are surprisingly quick.

I have two e92 DCTs - one w/ stock 3.15 FD and one w/ 3.62 FD. No comparison between the two. 3.62 makes a noticeable difference in all gears. Best mod I’ve added. Makes 6th and 7th useable when cruising. Both are stage 2 tuned w/ 8600 rpm redline. The extra 200 rpm also makes a noticeable difference. Always hit the stock rev limiter when stock tune is reinstalled for emissions testing.

[e92ben]

4.10 makes a huge difference. Wouldn’t go any more then that.

[Redd]

Y'all 3.62 guys are making me regret my 3.45 a lil bit lol. 3.45 is still a great FD especially for daily driver which my car is. Really woke up the engine, and I could still hit 270kmh / 167 mph with the 3.45 (speed laws are lax here). But I'm wondering if I should have just gone 3.62.