Setting up a ring and pinion is done by reading the pattern, not by feel. Painting the teeth with marking compound and rolling the gears shows exactly where the pinion is riding, which tells you whether to move shims for depth or adjust backlash before you button up the housing. Skipping this step is how a fresh gear set ends up howling.

Mopar Accessories 04883065AB Ring and Pinion Gear Marking Compound Features:

• Brightly colored compound formulated to leave a readable contact pattern on gear teeth.
• Used during assembly and adjustment of ring and pinion preload, pinion depth and backlash.
• Bright yellow color gives high contrast against the gear face.
• Supplied in a 4 ounce brush-top can for direct application, sold individually.
• Supersedes part number 04883065.