He's asking about the final drive ratio - the correct answer would be something like 3.23 or 2.85 or 3.69. Robert Nitchke's Production Data Book usually has it, but the book seems to be getting hard to come by. Maybe your dealer parts guy could look it up. Also, can you get the rear end up in the air, turn the rear wheels and count the driveshaft revolutions? I would think the 4.5 would be geared taller than the 3.5, if different. This seems to be the MB philosophy - the more torque the taller the gearing.