I don't think the ZF is any more reliable than the Getrag. It's certainly not rated for nearly as much torque. The M3 one should be far more durable, as it's the same transmission that's in the E39 M5. The only reason M3 racers do 5-speed swaps is because they're lighter and easier to find spare parts for (on a race car, you will go through a few synchros). As far as I know, the synchros are a bit weak on the ZF transmission. 2nd gear tends to bind
I have never heard of a street M3 with a 5-speed swap.
Last edited by TerraPhantm; 02-10-2013 at 01:08 PM.