I have an 87fj60 that goes from 4Low to 2Low--my understanding is that this is a jerry-rigged modification. True? The problem is that it can slip with a bang from 4low to 2low--and I CAN'T have this happen. How do I remove the 2Low option? Or prevent it from slipping? Looking underneath, I can't see any 'modifications.' What am I up against?