Regear Break-In: The First 500 Miles

The heat-cycle protocol new gears need, the 500-mile fluid change, and what noises are normal vs not.

New ring and pinion gears don't slide — they bed in. The tooth surfaces are microscopically rough from manufacturing, and the first few hundred miles polish them under load. Overheat them before that polish happens and the surfaces score; scored gears whine forever and wear fast. Break-in is heat management, nothing more mystical.

The protocol

First drive: 15–20 minutes, gentle acceleration, varied speeds, no highway drone. Then park it and let the differentials cool completely — an hour minimum.
Repeat for 2–3 heat cycles. Short trips are your friend for the first 100 miles.
No towing for the first 500 miles. Trailer load is sustained tooth load — exactly the heat scenario break-in exists to avoid. (Some gear makers say 1,000; their instruction sheet outranks this page.)
Vary speed on longer drives; skip cruise control so load fluctuates.
500 miles: change the gear oil. This is not optional maintenance — the break-in wear metal is in that oil, and it has to leave. Inspect what drains: fine grey paste on the magnet is normal; chips and flakes are a warranty conversation.

Sounds: normal vs not

Faint whine on light throttle that fades over the first weeks — surfaces polishing; common, usually harmless.
Whine that grows louder, or howls on deceleration — pattern or preload problem. Call the installer early; pattern issues don't heal.
Clunks on turns after a lunchbox locker install — that's the locker ratcheting, not the gears.

After the fluid change

Re-check pinion-nut torque and cover bolts, then drive it like you own it — towing included. The Decision System keeps this protocol as a checklist that saves your place, alongside your install records.