We first posted this info on swapping an M50 motor into an E30 chassis over 20 years ago.
US M50 Motor into e30 Chassis Transmission There are two options for the transmission. One is the e36 318 or 325 transmission, which can be connected directly to the original e30 5-speed driveshaft.
Alternatively, there is the e36 M3 transmission; it’s beefier, but adds a weight penalty. In addition, it is necessary to acquire either an e30 M3 5-speed driveshaft or a ’97 e36 M3 5-speed driveshaft.
As shown in the picture below, we used the 320i transmission mounts with an old 2002 trick: machined aluminum cups over the mounts to eliminate excessive movement under braking (#TMU3036, available in our catalog). Both the e36 318/325 or the M3 transmission can hook up with the support shift linkage and shift lever from an e36 5-speed M3. The original e30 back support is used for the bracket.
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