Drivetrain

It's great that your engine produces all that lovely power, but getting it to the Wheels is a serious matter. To make the bridge between them, you need to understand the Drivetrain.

Overview

The gearbox, propshaft and differential make up the drivetrain. To get power to the gearbox, the clutch presses itself up hard against the flywheel of the engine.

Gearbox

Gearbox ratios are also dependent on the ratio of your diff. For example, a high ratio diff (4.27) combined with a high-ratio first gear (3.72) will make first gear useless. In contrast, a low-ratio diff (3.25) with a low-ratio gearbox (2.48 in first)

The E30 was available as both a Manual and an Automatic. In total, seven different gearboxes were fitted to the E30; Four manuals, all produced by Getrag, and three automatics by ZF.

Manual

A range of gearboxes were used in the E30.

Manual Gearboxes

	Four-Speed	Five-Speed
	316 318i	316 316i 318i 320i 324d	318iS	323i Sport	323i 324td 325e 325i 325iX	325i Sport
1st	3.76	3.72	3.72	3.76	3.83	3.72
2nd	2.04	2.02	2.02	2.33	2.20	2.02
3rd	1.32	1.32	1.61	1.32	1.40	1.32
4th	1.00	1.00	1.00	1.23	1.00	1.00
5th		0.81	0.80	1.00	0.81	0.80
Reverse	4.10	3.45	3.71	4.10	3.46	3.46
	Getrag 242	Getrag 240 or 242/5	Getrag 240	Getrag 245	Getrag 260	Getrag 260/5

The M42 engine mates up to the same gearbox used in M40 engines, but is not campatible with earlier M10 gearboxes due to the angle of installation, which will cause problems with the shifter and rear gearbox mount.

Notice the similar ratios between the Getrag 240 and the Getrag 260/5. This means that for those replacing their M20B20 engine with the more powerful M20B25, Sports performance can be achieving by keeping the original gearbox.

However, don't let parts sellers convince you that the boxes are identical. Getrag gearboxes can be identified by looking for the serial number stamped around the edge of the bell housing. This number should also contain letters, which will identify the following boxes:

• Getrag 240 - MN or BMV
• Getrag 242 - LF, MD or BMU
• Getrag 242/5 - AY, AW or LG
• Getrag 245 - BJ
• Getrag 260 - NW, ANB or TNW
• Getrag 260/5 - TNN or HM

Automatic

Automatic Gearboxes

	Three-Speed	Four-Speed
	316 318i	320i 323i	325i
1st	2.48	2.73	2.48
2nd	1.48	1.56	1.48
3rd	1.00	1.00	1.00
4th		0.73	0.73
Reverse	2.09	2.09	2.09
	ZF 3 HP 22	ZF 4 HP 22

Differential

Main article: Differentials

Output Flanges

Output flange and drive shaft

Common Upgrades

A Z3 short shift conversion will help you change gears quicker.