I searched and came up blank. The Getrag 6-Speed in the Cooper S is quite a bit different than most 6-speed transmissions:

"When the engineers attempted to slot in a conventional six-speeder, it wouldn't fit. So Getrag came up with an alternative, similar to the one employed by the six-speed Audi TT, that groups the ratios in two sets, each with it's own final drive. Thus 1-2-5-6 are on one shaft, and 3-4-Reverse on another, with third and fifth, and fourth and sixth ratios duplicated."

I don't understand, and cannot picture what they are talking about. I'm usually pretty good with understanding this stuff - but this, no idea.

Can anyone dumb it down for me, or give me more specifics, or a picture or a diagram, or links to the Audi TT transmission, or a Getrag link. No urgency, I just like to know how my cars work, and this one baffles me.

Two sets of gears are the same, but when routed through different final drives, you get different OA gearing. Sounds like a multi-speed bike - say, five gears on the rear, two on the front. Shifting from 3rd to 4th on the MINI would be like shifting from 5th to 10th on the bike. I've heard that the gearing is quite tall, which is kind of weird, in a 6-speed. Second gear is good for 60mph.

I got an answer to your question when I asked MINI tech support why there are different types of numbers for the gear ratios for the Cooper and the S. Their reply was:

The MINI Cooper S uses a three-shaft Getrag transmission
verses a two shaft conventional transmission. This
transmission has two output shafts geared to the
differential.

The gears on the input shaft from the engine drive the output shafts and the differential through different
final drive gears. So there is a 2.75:1 final drive for
1st, 2nd, 5th and 6th gear on one shaft and a 4.05 final drive for 3rd, 4th and Reverse on the other output shaft.
(Imagine the differential gear, with two seperate
gears on opposite sides.)

So depending on the gear you have selected, the final drive ratio varies (either 2.74 or 4.05). So publishing a
conventional gear chart can't be done. For example, both
3rd and 5th are 1.333:1, and 4th and 6th gear are 1.089:1,
but they are on two different output shafts with different final drives. People thought when we publish the same ratio
for two gears, it was a typo. So what we have published are the overall gear ratios (gear ratio multiplied by the
included respective final drive)

===== end of reply from MINI support ================

Same answer as the previous reply, just more info to help you visualize the gearing (I hope).

Actually RickB and Arizona Cooper S, posts explained it very well, here is a another rehash from me plus a schematic for us slow learners. :D

The Getrag 6-sp manual transaxle is comprised of a gearbox containing 6 forward gears + reverse and a differential contained in the same case. Like the 5-sp gearbox on the Cooper, the Getrag contains a main shaft (input shaft), but has two layshafts (countershafts-UK) driving the differential ring gear instead of just one in the 5-sp. So when you select a gear on the Getrag the shift forks engage one primary gear + one of two layshaft gears.

RickB's analogy of a bicycle is a good way to describe the shift action. Here's how I would distinguish between the 5-sp and the 6-sp. Imagine a five speed bicycle with 5 chainrings on the crank arms and just 1 sprocket on the rear wheel, instead of the conventional layout. Then to shift gears, you would shift the front derailleur to one of the five chainrings. That would be similar to the 5-sp transmission. Then think of a bicycle with 4 chainrings on the crank arms, and 2 sprockets on the rear wheel, which gives you a total of eight possible speeds. But now to shift gears you need two derailleurs---one on the front and one on the rear. But 2 of the 8 speeds are not needed because there are four ratios that are overlapping between 1st and 2nd. Delete those two redundant ratios, and you are left with six useable speeds. This would be similar to the Getrag 6-speed transaxle.

Below is a drawing of a twin layshaft six speed manual transmission, courtesy of carseverything.com., with the MINI's gear ratios for the 6-speed.

http://www.mini2.com/forum/attachment/php?=&postid=51563

RickB, the Bicycle analogy helped me understand the theory, and solidified that my guess at how it worked was pretty close.

Arizona Cooper S, thanks for the official info - good to know, but a little fuzzy for me to visualize.

Karmuze, hats off. I appreciate your description, but the real solid gold answer of the day goes for the picture you found. I looked and looked for a picture, cutaway, diagram, etc... That did it, 100%, I get it now. I could even explain it to someone else.

Thanks all,
This is a great little (not so little anymore) forum.

Shoot. That answer gave me more questions. Since there are now two layshafts, are they allways attached to the differential? I.E. more metal to spin-up than on a regular 5-Spd? If not, are there more syncromeshes required on this configuration?

Just wondering, because since the 'close-ratio' on the Cooper S isn't all that close, and seems fairly tall geared overall, is the 6-Spd really an advantage? Sure it was necessary to source a new tranny because the old Rover 5-Spd would never last under the S's load conditions, but with the extra layshaft, doesn't this increase spinning weight? Or is it insignificant overall?

Also, does this explain the 2-3 and 4-5 hesitation my testor Cooper S exhibited? It was, for lack of a better word, kinda 'thick' making these two specific shifts. Only noticeable when speed-shifting.

Thanks for your help you guys.

This type of gearbox is also going to be installed in the new SVT Ford Focus.Actually the Ford gearbox is also a Getrag,but the overall ratios will be different because the Focus engine will have more power than the MINI's.The gearbox appears to be a nice piece of engineering,but talking to a few ford engineers,the getrag transmission isn't as strong as some of the five speed boxes on the market.I believe this is why the WRC Focus uses a five speed.Anything much more than 170 horsepower,the getrag unit is not going to hold up.I guess we will find out just how much it will take in the next few months.

Hmm. Interesting. I wonder what this means for the 200+BHP of the S Works?

I know to my own cost that when the engine is souped up without making changes to the gearbox, you end up with a big bill after a few thousand miles ...

My understanding was that the Getrag unit was chosen after reliability problems with the 5-speed in the S - ie the extra HP chewed up the 5-speed, and a stronger unit was required. It would be a pity if they've chosen a unit for the S that can handle the standard HP but no more. :confused:

I read somewhere that BMW originally had the Cooper S running at around 200BHP, but they detuned it to bring the fuel consumption up, to save the drivetrain and to bring the noise/emissions down for an everyday car.

Andy

Originally posted by An_S_4_Me
I read somewhere that BMW originally had the Cooper S running at around 200BHP, but they detuned it to bring the fuel consumption up, to save the drivetrain and to bring the noise/emissions down for an everyday car.

Andy

This adds weight to the question around whether the std transmission is man enough for the Works conversion

The 5-Spd currently in the MINI (Rover-sourced?) is particularily small and brittle. It can handle up to about 150 HP.

The Getrag unit is beefier, but I don't know by how much. It is still a compact unit. Apparently it is used in the Audi TT and the SVT Ford Focus (Focus ST170 in UK).

But, now we hear that most regular 5-Spd tansmissions are tougher than the Getrag? Interesting. What are we comparing to? Sure the 5-Spd in our old Mustang handled our uprated 314 BHP day in, and day out, never fussed, but it was WAY too large to fit in a MINI. So, what FWD integrated transmissions are tougher?

And the 200 HP Cooper S was down-rated mostly for reliability purposes, over the consumption and emmissions reasons. I'm sure it saved the tranny, but I thought it was to ensure the engine could easily go 150,000 miles without trouble.

P.S. What is the max HP of the quickest 6-Spd Audi TT? That might give us a clue.

If you have questions,this might help.I went to Getrags web site,www.getrag.de and looked up the phone number for the headquaters.The headquarters is located in Untergruppenbach,Germany.The phone is +49(0)7131/64440.If someone can phone them get a hold of someone in customer service,ask for a product data sheet on the transmission.The data sheet should tell you how much horsepower the transmission can take.Better yet,ask to speak to a development engineer who worked on the damm thing,then you will get all your answers.I would call them,but I don't speak german.I'm sure someone there can speak english,but it would be faster to do it in german.
Check out the web site.The site can be translated into english and italian as well as being in german.Sorry,no french.

Originally posted by noahe

Shoot. That answer gave me more questions.

When you talk about changing gears in a manual transmission, you're really saying that you are selecting a PAIR of gears---one primary gear on the input shaft that is driving one secondary gear on the layshaft(countershaft-UK). The difference in the diameter of the two gears is what gives you the gear ratio---3:1 for example, would mean the primary gear is 1/3x the diameter of the secondary gear. Or another way to look at this would be--the primary gear has to rotate 3x times for every 1x time that the secondary gear does. That would be an example of a low gear(high ratio) like a 1st gear. Modern manual transmissions are constant-mesh types in which all 7 pairs of gears, in a 6-speed, are turning whenever the input shaft from the engine is turning. Either the primary or secondary gear of each gear set must rotate freely on its shaft because of the constant-mesh design.
Engagement of a gear happens when the shift fork moves a synchronizer assembly to lock the free rotating gear to its shaft, thus selecting that gear pair to drive the output shaft to the differential. Each synchronizer can be moved left or right to select two different gear sets in turn. So a 6-speed transaxle would require 3 synchros to select 6 different ratios. However, I read a Focus SVT article that said that the SVT Getrag™ has a synchronizer on reverse gear as well, which is very unusual. Since the same transaxle in used in the MINI, although with different gear ratios, I would expect that reverse gear in the Cooper S is also synchronized. That would require 4 synchros for the 7 gear sets instead of the three you would think necessary.

There are many different designs of transmission and the twin layshaft type is a rare breed. I have not found any exploded views or actual cutaway pictures of this style of gearbox. So with that in mind, the following is only my guess on how the MINI 6-speed functions, and I am open to anyone correcting any false assumptions (likely) in my description.

It looks like the input shaft would have 4 primary gears attached to it. Each of those gears would drive two secondary gears---one on layshaft 1 and one on layshaft 2. Since there are only 3 secondary gears on layshaft 2, then one of the primary gears would not drive two other gears, but rather just one. Each layshaft would end in a final drive gear engaging the differential ring gear (crownwheel-UK), with its respective final drive ratio---either 2.74 or 4.05. Each layshaft would then have two synchros. Note in this scenario there would be a total of 14 individual gears including the two layshaft final gears and reverse idler gear, whereas in the 5-speed gearbox there would be 13 individual gears.

Below is a cutaway drawing of a Honda 5-speed transaxle that shows a layshaft engagement of the differential ring gear.


http://a332.g.akamai.net/f/332/936/12h/www.edmunds.com/media/ownership/tech_center/transmission_basics/honda.insightimasystem.175.jpg (http://www.mini2.com/forum/attachment.php?s=&postid=51559)

In summary, I would say that the rotating mass of the 6-speed is marginally more that the 5-speed, for the 1 extra gear and 1 extra syncro. Since the last two ratios are both what could be considered overdrive ratios, the 6-speed IMO is a cruising gearbox and not a high performance racing type gearbox.

The friendly folks at Getrag got back to me. They gave me a diagram and a simple description... Very nice of them.

Anyways, it's no where near as good as the descriptions I got here, or the most excellent diagram Karmuze searched out, and posted for us. MINI2 is still the best by far, but for the curious, here is the Getrag info:

1 input shaft

2 layshafts = "output" shafts

output no. 1 (with ratio "1") for 1st, 2nd, 5th and 6th gear
output no.2 (with ratio "2") for 3rd, 4th and rev. gear

1 final drive gear in the differential = the 2 layshafts and the final drive form a triangle, both layshafts go on the same final drive gear, thus

=> no. of gears on layshaft no. 1 x no. of gears on FD = FD ratio no. 1
=> no. of gears on layshaft no. 2 x no. of gears on FD = FD ratio no. 2.

Originally posted by noahe
The 5-Spd currently in the MINI (Rover-sourced?)

It's supplied by BMW Midland Gears Limited and NOT MG-Rover (and hence built to BMWs more exacting standards).

Thanks noahe, for confirming my guess with the information from Getrag™--some days it pays to be lucky rather than good. Did your correspondence happen to reveal the manufacturing site where the 6-speed is built?
=> no. of gears on layshaft no. 1 x no. of gears on FD = FD ratio no. 1
=> no. of gears on layshaft no. 2 x no. of gears on FD = FD ratio no. 2.
I think something got lost here in the translation from Deutsch to English. What was meant is I believe:

=>teeth on Ring Gear / teeth on layshaft #1 FD gear = final drive ratio 1
=>teeth on Ring Gear / teeth on layshaft #2 FD gear = final drive ratio 2

Here's a cutaway of the 6-speed gearbox used on the Focus SVT that I found from focaljet.com BB:

Originally posted by karmuze
Did your correspondence happen to reveal the manufacturing site where the 6-speed is built?
Nope. That cut-away of the Focus SVT's tranny is pretty good. Apparently, the Audi TT, Focus SVT, and MINI Cooper S all have nearly the same unit. Different mounting flanges and such, but same core technology.

Here are some more pics of the 3-D gearbox of the MCS, the Getrag 285. It's an ultra-short transmission, only 322 mm long, including the 100 mm spave the clutch need.
The problem for this gearbox won't be the hp, but it is limited by torque figures. It can only have a max. torque of 225 Nm (for now, but Getrag is planning to make it stronger in the future). So there's not a lot of space for that with the 210 Nm figure of the MINI Cooper S. The Ford ST170 (SVT) only uses 196 Nm.

And here's a cut-away pic of the Getrag 285:

The Audi TT in its most potent stock form is 225 hp at the crank but is easy to upgrade to +/- 250 hp. Not too many instances of failure either. Let's hope the units ARE similar.