Don't Forget to Pack

Axle, Rex and Sandy the Bulldozer decide to build a jump. They usually have Fill the Front-loader's help, but since Fill is busy helping Strut, they decide to do it without him. The problem is, when they build it the dirt that makes the jump seems to be too soft for Axle to drive on. They try changing the shape of the jump, but that doesn't help. When they drive away looking for answers, Zack comes along the jump and drives over it several times. When they get back they see tire tracks on the jump and realize it works better than it did before. Fill finally joins them and they find out that he always packs down the dirt as the last step in making a jump. That's why it worked better after Zack had driven on it.