The 328xi has the heavier-duty Getrag Type H transmission, with slightly different ratios, not for performance or economy reasons, but because of internal design factors.

Because of its performance potential, the 335i is fitted with the still more robust

ZF Type G gearbox, but with "taller" 1st-4th ratios that take advantage of the N54 engine's torque and allow this high-performance model to attain higher speeds in each of these ratios. This effect is furthered by the 335i's numerically lower final drive ratio (335i 3.08:1, 328i 3.23:1).

In all three transmissions, 5th gear is direct (1.00:1), and 6th gear is an overdrive for quietness and fuel efficiency at cruising speeds. All 3 Series manual transmissions offer several tangible benefits:

- Highly effective synchronization of shifting
- Light, pleasing feel as the shift lever is moved from gear to gear
- Sporty shifting, via short shift "throws" from neutral to each gear
- Use of lifetime transmission oil, which never needs to be changed
- "Clean bearings" design; protects bearings from contamination, ensures adequate lubrication at all times and therefore enhances durability.

The new 3 Series Coupe now joins other BMW Series in offering the 6-speed STEPTRONIC automatic transmission. Compared to the 5-speed unit it replaces, it's lighter, has a more effective torque converter, operates with fewer internal clutches, and can reduce fuel consumption, particularly at cruising speeds when 6th gear is in frequent use. In the 335i, and to appear in other models later, the automatic is the familiar ZF 6 HP 19, but in the new TU, or Technically Updated, form. 

As in all other current BMW automatics, the STEPTRONIC feature offers drivers a choice of Normal, Sport and Manual modes. Park, Reverse, Neutral and Drive ranges (P-R-N-D) are in the right gate of the shift lever. The Sport mode, in which shifts occur at higher engine speeds, is engaged by moving the lever leftward from D; the Manual mode is engaged when the driver manually chooses a gear by tipping the lever (or shift paddles) forward (for downshifts) or rearward (for upshifts).

Compared to the existing ZF 6 HP 19, as found in 2006 model year 3 Series Sedans and Sports Wagons, the TU has significant improvements:

- More effective damping of torsional vibrations in the torque converter, which have made it possible to keep the converter's lockup engaged more of the time. This means less slippage; the resulting fuel economy improvement is about 3%, and the driver experiences sharper response to the accelerator pedal.

- Quicker shifting response to the driver's performance demands - up to 40% quicker. This is satisfying to the driver, who experiences less lag between the time the accelerator pedal is depressed and the shift lever (or shift paddles) moved and the actual occurrence of a shift.

- Quicker shifts. Once a shift is actually initiated, the time it takes to complete the shift is reduced up to 50%. This was accomplished via a new hydraulic shifting system and more sophisticated electronic software.

- Finer adaptation to driving style and conditions. Within the Adaptive shift control, which adjusts shift characteristics to these variables, there are now three stages vs. the previous two.

This transmission has two additional features, both of which enhance enthusiastic driving:

- Direct selection of Manual mode. If, while driving in D, the driver manually downshifts via paddle or shift lever, the Manual mode engages. But if the driver makes no further manual shifts within 15 seconds, the transmission returns to automatic operation. This feature was first introduced on the '06 Z4 Roadsters and Coupes. 

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