Driveshaft Half-shafts

If you’re thinking of swapping out your 4 banger for a 6, there’s several things you’ll need to change over in order to make the engine swap work. One of which, is the shortening of the driveshaft. 6 cylinder E30’s have a shorter driveshaft, due to having a longer gearbox. As such, you have two options. Either get your 4 cylinder driveshaft modified and balanced to fit, or find a 6 cylinder driveshaft. I opted for the latter, and upon inspection discovered two things.

The half-shaft that connects to the diff is actually the same for both the 4 cylinder and 6 cylinder driveshaft (both length and thickness in regards to diameter), it’s only the gearbox side half-shaft that differs in length and thickness.

The half-shaft that differs in length (connecting to the gearbox) is thinner for the 6 cylinder, and the 4 cylinder half-shaft is thicker.

One thing to keep in mind here, which will be discussed more in detail when I talk about the centre bearings, is that the 6 cylinder driveshaft I have is from a series 1 E30, and the 4 Cylinder is from a series 2. Also while the half-shaft for the 4 cylinder may look thicker and stronger, the shaft is hollow and could possibly be weaker. External looks are not always a good indication of strength. Best off using a 6 cylinder driveshaft with a 6 cylinder, and a 4 with a 4 respectively. The images comparing these can be seen below.