I am currently in rebuild mode on my 87 300D so my engine is out of the car. I had to remove the water pump pulley since the balancer slightly interferes when attempting to remove. The balancer/crankshaft bolt loosened easily with the right size socket and a long breaker bar. The threads were normal rotation. You must be able to hold the crankshaft in position when removing the bolt. I used a piece of wood to block the crankshaft journel, no problem. With the engine in the car, one way is to remove the starter and I believe MBZ makes a tool to lock the flywheel throught the starter hole. Otherwise, you may be able to go through the bottom of the bell housing cover and somehow lock the flywheel. Good luck!