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      01-06-2009, 05:36 AM   #1
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Stock gear ratios & final drive gearing

I am so confused with different / controversial info I have read over time on this.

Does anyone know what are (i) the gear ratios, and (ii) the final drive (differential) gearing, for stock 6MTs and DCTs?

On gear ratios I remember reading somewhere in this post that
MT6: 4.06, 2.37, 1.58, 1.19, 1.00, 0.87
DCT: 4.78, 2.93, 2.15, 1.68, 1.39, 1.20, 1.00
Is this right?

On the final drive I am a bit confused with various numbers. Does anyone know?

I am only talking stock please.

Thanks in advance!
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      01-06-2009, 06:18 AM   #2
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6MT

1st: 4.055:1
2nd: 2.369:1
3rd: 1.582:1
4th: 1.192:1
5th: 1.000:1
6th: 0.872:1

Final Drive: 3.846:1
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      01-06-2009, 06:22 AM   #3
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Quote:
Originally Posted by FStop7 View Post
6MT

1st: 4.055:1
2nd: 2.369:1
3rd: 1.582:1
4th: 1.192:1
5th: 1.000:1
6th: 0.872:1

Final Drive: 3.846:1
Nice & simple - many thanks!!!
Anyone for the DCT?
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      01-06-2009, 02:31 PM   #4
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MDCT
1-4.780
2-2.933
3-2.153
4-1.678
5-1.390
6-1.203
7-1.000

Final drive- 3.154

http://www.m3post.com/goodiesforyou/mdctinfo.PDF
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      01-06-2009, 02:56 PM   #5
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Quote:
Originally Posted by PencilGeek View Post
Ah, but what are the tooth counts of each gear? I've been trying to find that for 9 months. Nobody seems to know.
Would the number of teeth make a difference?
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      01-07-2009, 08:59 AM   #6
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Quote:
Originally Posted by FStop7 View Post
6MT

1st: 4.055:1
2nd: 2.369:1
3rd: 1.582:1
4th: 1.192:1
5th: 1.000:1
6th: 0.872:1

Final Drive: 3.846:1
Quote:
Originally Posted by gobuffs View Post
MDCT
1-4.780
2-2.933
3-2.153
4-1.678
5-1.390
6-1.203
7-1.000

Final drive- 3.154

http://www.m3post.com/goodiesforyou/mdctinfo.PDF
That's brilliant - thanks guys!!!

I just wanted these to calculate the speed of the 6MT & of the DCT at any given gear & engine rpm, which I did in an excel spreadsheet and seems to be working (I cross checked my findings for the 6MT with a couple of magazines that report top speed for each gear).

According to my calculations, the (theoretical) top speed at 8,400rpm for the stock 6MT and DCT is 302km/h and 321km/h respectively (assuming that the engine is allowed to rev up to the redline in the top gear on each car and assuming that it has enough power!).
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      01-07-2009, 10:47 AM   #7
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Quote:
Originally Posted by gr8000 View Post
That's brilliant - thanks guys!!!

I just wanted these to calculate the speed of the 6MT & of the DCT at any given gear & engine rpm, which I did in an excel spreadsheet and seems to be working (I cross checked my findings for the 6MT with a couple of magazines that report top speed for each gear).

According to my calculations, the (theoretical) top speed at 8,400rpm for the stock 6MT and DCT is 302km/h and 321km/h respectively (assuming that the engine is allowed to rev up to the redline in the top gear on each car and assuming that it has enough power!).
That sounds about right, but, say you increase hp to well above 500, would the top speed still be limited by the gear ratios?
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      01-07-2009, 10:57 AM   #8
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Quote:
Originally Posted by BMW-M-Mexico View Post
That sounds about right, but, say you increase hp to well above 500, would the top speed still be limited by the gear ratios?
yep (limited by the gear ratios & by the 8,400rpm limiter of course)
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      01-07-2009, 11:24 AM   #9
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Quote:
Originally Posted by gr8000 View Post
yep (limited by the gear ratios & by the 8,400rpm limiter of course)
Sure, rev limited as well. Thanks
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      01-07-2009, 09:18 PM   #10
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I never understood anything about gear ratios
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      01-08-2009, 08:04 AM   #11
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Quote:
Originally Posted by MosesDKE View Post
I never understood anything about gear ratios
The basic idea is pretty simple: A gear ratio of 1:2 means that the output shaft gets half a revolution for every revolution of the input shaft!
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      01-08-2009, 10:53 AM   #12
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Quote:
Originally Posted by gr8000 View Post
The basic idea is pretty simple: A gear ratio of 1:2 means that the output shaft gets half a revolution for every revolution of the input shaft!
Thanks, that helps. And the final drive? What is that exactly?
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      01-08-2009, 10:53 AM   #13
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Quote:
Originally Posted by gr8000 View Post
The basic idea is pretty simple: A gear ratio of 1:2 means that the output shaft gets half a revolution for every revolution of the input shaft!
Simple and clear, thanks again.
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      01-08-2009, 11:13 AM   #14
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Quote:
Originally Posted by Kobaiyashi View Post
Thanks, that helps. And the final drive? What is that exactly?
The final drive is the gearing in the differential.
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      01-08-2009, 11:19 AM   #15
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Quote:
Originally Posted by gr8000 View Post
The final drive is the gearing in the differential.
OK even clearer now.
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      01-08-2009, 11:26 AM   #16
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Quote:
Originally Posted by gr8000 View Post
The basic idea is pretty simple: A gear ratio of 1:2 means that the output shaft gets half a revolution for every revolution of the input shaft!
You're a GENIUS for clear explanation

Thanks mate
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      01-08-2009, 11:42 AM   #17
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Quote:
Originally Posted by Mischievous M View Post
You're a GENIUS for clear explanation

Thanks mate
Are you guys serious or you kiddin me?!
I never thought this is such a complex matter in the first place but whatever... Glad I made this clear!
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      01-08-2009, 11:47 AM   #18
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Quote:
Originally Posted by gr8000 View Post
Are you guys serious or you kiddin me?!
I never thought this is such a complex matter in the first place but whatever... Glad I made this clear!
No hint of sarcasm buddy

I never understood the entire ratios of gears until you've clear it up a lot better with a crisp to the point statment.

Thanks... am reading a lil more about it on howstuffworks.com
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      05-19-2010, 01:42 PM   #19
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Quote:
Originally Posted by gobuffs View Post
MDCT
1-4.780
2-2.933
3-2.153
4-1.678
5-1.390
6-1.203
7-1.000

Final drive- 3.154

http://www.m3post.com/goodiesforyou/mdctinfo.PDF
can someone post the respective top speeds 4 each gear for a dct car?

thanks
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      05-19-2010, 02:16 PM   #20
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Quote:
Originally Posted by disruptv View Post
can someone post the respective top speeds 4 each gear for a dct car?

thanks
http://www.google.com/search?q=speed...www.m3post.com

http://www.m3post.com/forums/showthread.php?t=292787
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      05-19-2010, 02:30 PM   #21
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      05-19-2010, 03:21 PM   #22
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Is it still impossible to upload MS excel files on this forum? What a pitty...
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