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Gear Ratios

Overall gear ratios for Fortwo and Roadster. Thanks to Blackdog for the original ratios and thanks to Bettina from Getrag for supplying the new fortwo ratios and final drive info.

Modification Details




Smart ForTwo 450

  Petrol Brabus Diesel
  599cc 698cc 698cc pre-2006 2006
1st gear 14.203 13.230 13.230 12.375 12.375
2nd gear 10.310 9.604 9.604 8.983 8.983
3rd gear 7.407 6.899 7.350 6.453 6.875
4th gear 5.625 5.235 5.796 4.566 5.235
5th gear 4.083 3.800 4.208 3.315 3.800
6th gear 2.933 2.730 3.220 2.381 2.908
Reverse 12.888 12.005 12.005 11.229 11.569
Final Drive 1 4.208 3.920 3.920 3.667 3.667
Final Drive 2 1.667 1.551 1.717 1.353 1.353

Smart Fortwo 451

  999cc 800cc
  N/A Petrol Turbo Petrol Brabus Diesel
1st gear 13.912 13.909 14.982 13.755
2nd gear 8.664 8.664 8.664 7.954
3rd gear 5.697 5.697 5.697 5.231
4th gear 4.271 4.271 4.271 3.709
5th gear 3.456 3.202 3.456 2.674
Final Drive 4.529 4.529 4.529 4.158
Reverse 14.633 14.633 14.633 13.434

smart Roadster

  kW
  45 60 & 74
1st gear 13.230 13.230
2nd gear 9.604 9.604
3rd gear 6.899 7.350
4th gear 5.235 5.796
5th gear 3.800 4.208
6th gear 2.730 3.220
Reverse 12.005 12.005
Final Drive 1 3.920 3.920
Final Drive 2 1.551 1.717

Crossblade

  599cc
1st gear 14.203
2nd gear 10.310
3rd gear 7.407
4th gear 5.625
5th gear 4.083
6th gear 2.933
Reverse 12.888
Final Drive 1 4.208
Final Drive 2 1.167

Forfour 5 Speed Manual

  Petrol
  1.1/75bhp 1.3/95bhp 1.5/109bhp 1.5/177bhp
1st gear 14.398 13.753 13.753 13.753
2nd gear 8.327 7.954 7.954 7.636
3rd gear 5.476 5.231 5.231 5.021
4th gear 4.104 3.92 3.92 3.838
5th gear 3.322 3.173 3.173 3.114
Reverse 14.063 13.433 13.433 12.545

  Diesel
  1.5/68bhp 1.5/95bhp
1st gear # #
2nd gear # #
3rd gear # #
4th gear # #
5th gear # #
Reverse # #
 

Forfour 6 Semi Auto

  Petrol Diesel
1st gear 3.071 3.308
2nd gear 1.913 1.913
3rd gear 1.258 1.219
4th gear 0.943 0.846
5th gear 0.763 0.651
6th gear 0.643 0.543
Reverse 3.231 3.357


Final Drive On The Five Speed 451 Gearbox

Final drive is the fixed ratio that sits between the gearbox and the drive shafts.
All of the figures above have been calculated with final drive already.

For example, first gear of the Brabus 451 is 3.308, multiply this by the final drive ratio of 4.529.
3.308 x 4.529 = 14.981932 which is rounded up to 14.982

Therefore if you take the above precalculated figures and divide them by the final
drive ratio you will arrive at the true gear ratio for each gear in the transmission.

Final Drive On The Six Speed Gearbox

The Fortwo and Roadster gearbox is unlike many other gearboxes as it had two final drives.
Although it is a six speed gearbox, it only has three gears in it. This is doubled by the two final drives.

Gear 1 = Gear 1 + FD1
Gear 2 = Gear 2 + FD1
Gear 3 = Gear 3 + FD1
Gear 4 = Gear 1 + FD2
Gear 5 = Gear 2 + FD2
Gear 6 = Gear 3 + FD2

This made the gearbox smaller but slowed it down as it had to change more cogs.

Reverse Gear

Reverse uses two gears and final drive 1. The engine obviously doesn't spin backward
in reverse which is why it uses two cogs before the final drive to reverse the rotation.

The reverse gears are the same in all six speed gearboxes, from 599cc fortwo to Brabus Roadster.

1.5625 (25/16) x 1.960 (49/25) x FD1.

Brabus Gearbox In A Non Brabus Smart

It still isn't widely known but you can't just put a Brabus gearbox in a non Brabus smart.
What happens is the car is usually happy to drive in gear 1, 2 and 3 but as it switches over to final drive 2, the gearbox speed is wrong so the ECU calls it up as a shifting fault and shows 3 bars on the speedo.

Is The 451 Gearbox Faster To Change?

The biggest complaint on the original car (450) was the slow gearchange.
The 6 gears was reduced to 5 so a single final drive could be used and speed up the change.
The old system was controlled by the ECU, the new gearbox has a dedicated controller.
Couple that with the new software and you have a gearchange that is faster than the original.

Keith contacted me with the following information about the 451 gearbox.

The gear change is faster due to it having two motors involved in the changing gear operation.
One disengages while the other engages. This is the same set up as the smart forfour vehicle.
Plus they took a sensor out due to a improvement in gear change.

So... Is It Faster To Change Gear?

No, unfortunately not. My remapped 450 changed gear faster than my remapped 451.
So what smart have actually done is removed a gear which affect MPG when cruising at
high speeds but haven't improved the speed of the gear change to a point that can be felt.

A bit of a let down then?

Yeah, it's a backward's step abortion of a gearbox compared to the 6 speed on the 450 and 452.

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