they both use the same zf tranny, cept the m3 has a beefier clutch setup. the e35 325 uses a getrag 5spd, and a different clutch/flywheel setup. the new e46 328 and 330 use the same zf tranny as the e36 m3 as well, but with different cluch like the e36 328. euro e36 m3 and e46 m3 use the getrab 6spd that is also in use in the 540 6spd, e39 m5, and z8. m roadsters and coupes use the zf, as well as the z3 2.8 and 3.0. so the main difference is the clutch, which the m cars get the better unit.