2008 E-450 Differential identification
The owners manual says it could have either a limited slip OR a conventional axle. They use different fluids.
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Block both front wheels so the vehicle can't move. Jack up the rear axle till both rear tires are off the ground. Put jack stands under the rear axle and then make sure the trans is in neutral and the emergency brake off. Now go to one side of the rear tires and give a turn while watching the other side rear tires. If the both turn the same direction then you have limited slip, if they turn in opposite direction than you do not have limited slip but have an open differential.
