Overview & Design
Uniquely designed, this limited slip differential (LSD) is durable, versatile, and tuneable. Its sleek form gives it an unmistakeably modern and refined appearance.
The unit features a new pre-load spacer and multi-ramp ramp system, allowing precise adjustment for different driving styles and conditions. Other ramp configurations are available to order for specific applications.
By maximising the surface friction area and the number of coated ‘active’ clutch plates in use, this limited slip differential delivers exceptionally smooth and progressive engagement. Combined with outstanding traction control and power transfer, it offers one of the most refined and controllable driving experiences available for Austin Healey models.
Limited Slip Differential 45/90 Specification
Under Acceleration: The 45-degree ramp angle provides a moderate, progressive lock-up under power, offering smooth engagement and balanced traction.
During Deceleration: The 90-degree ramp behaves like an open differential during engine braking, with minimal locking similar to a standard differential.
Designed Application: Often referred to as a “1-way” or “1.5-way” setup (depending on interpretation of the 90-degree ramp), this configuration suits fast-road driving and occasional track days. It provides excellent traction under acceleration without making the car unstable during braking or corner entry.
Driving Feel: Predictable, balanced, and user-friendly for spirited road use.
Limited Slip Differential 30/90 Specification
Under Acceleration: The shallower 30-degree ramp delivers a quicker, more aggressive lock-up response under power for maximum traction out of corners.
During Deceleration: Like the 45/90 unit, the 90-degree ramp provides minimal or no locking on deceleration, maintaining stability under braking.
Designed Application: Favoured for motorsport use, including rallying and long-circuit racing, where maximum power transfer and acceleration traction are critical. The stronger lock-up effect can be more demanding to manage but rewards experienced drivers with superior performance.
Driving Feel: Performance-focused and responsive, requiring more driver skill and throttle control.
FAQs
Does this limited slip differential fit all Austin Healey models?
No. This LSD fits Austin Healey BN4, BN6, BN7, BT7, BJ7, and BJ8 models equipped with the Salisbury-type rear axle and 10-spline half-shafts. It is not compatible with early BN1 or BN2 cars that use the 4-stud axle and different spline count.
What oil should I use with this LSD?
Use a GL5-rated 80W-90 limited slip differential oil that includes a friction modifier. Standard gear oil is unsuitable, as it can cause plate chatter or premature wear.
Is professional installation required?
Yes, professional setup is recommended. Correct backlash, pre-load, and crown-wheel alignment must be checked during fitting. Inaccurate setup can cause noise or uneven wear. A specialist Healey or competition drivetrain engineer should carry out the installation.
Do I need to modify my axle housing or half-shafts?
No permanent modification is required if the car has the standard Salisbury axle and 10-spline half-shafts. Always confirm internal clearance and condition of bearings before installation, particularly when combined with non-standard crown-wheel and pinion sets.
What are the maintenance or service requirements?
The LSD is fully serviceable. Oil should be changed at regular service intervals, and the clutch plates inspected periodically for wear. Replacement plates are available, allowing the unit to be rebuilt without replacing the whole differential.
How will my Healey drive differently with an LSD fitted?
A limited slip differential improves traction by transferring power to the wheel with more grip, especially when accelerating out of corners or on uneven surfaces. The car feels more stable under power, with less wheelspin and smoother exit from bends. Steering effort may feel slightly heavier at low speeds, but overall balance and control are greatly improved once the car is moving.
FULL RACE