Differential Bearing Wear and Noise
Symptoms
A click or clunk from the rear that occurs once per wheel rotation, most noticeable at low speed when coasting to a stop. Or a continuous whining/humming that varies with road speed but not engine RPM (persists in neutral while coasting).
Cause
The A70 uses a Toyota 7.5-inch ring gear differential, rigidly mounted to the rear subframe with no bushings (unlike the A80 which has bushed mounts). This rigid mounting means any internal differential noise transmits directly into the cabin. Pinion bearings, carrier bearings, and the crush sleeve all wear over time. Cars that have been used for drag launches or drifting wear differential components much faster.
Fix
A differential rebuild with new bearings, seals, and crush sleeve runs $1,500-3,000.
Sourcing rebuild kits can be challenging, as the A70 diff doesn't share rebuild kit listings with common vehicles.
Toyota OEM bearings purchased individually are the reliable route, as aftermarket "kits" often have incorrect bearing sizes.
The factory ratio is 3.91:1 on turbo models and 4.30:1 on some NA models.
If changing ratios, the lowest aftermarket option available is approximately 3.54:1 (Nitro Gears).
For cars making serious power, differential failure is a real possibility.
The factory diff is rated for stock power levels.
High-torque builds (400+ hp) benefit from a diff cooler and regular fluid changes.
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