Shift lock is traditionally a consequence of bad track driving. But can be employed, with skill, to induce drift.
1. Enter the corner at speed to induce understeer.
2. Turn into the corner and stay on the power.
3. As the car begins to understeer, drop down a gear, but do NOT heal-and-toe.
4. The revs will quickly increase and the driveline will slowdown as engine revs try to match driveline revs.
5. The rear wheels will loose traction. You are now in drift!