Cusco LSD RS1.5 Front GDB(C) GRB GVB STI Impreza

Here’s a clear, practical breakdown of the advantages of the Cusco LSD RS1.5 Front when fitted to Subaru Impreza WRX/STI platforms like GDB(C), GRB, and GVB:

🔧 What It Is

The Cusco RS1.5 Front LSD is a mechanical limited-slip differential designed to replace the open front diff on AWD Subarus. It uses a multi-plate clutch setup with a moderate pre-load and torque-sensitive behavior.

🚗 Key Advantages

🌀 1. Better Traction Under Power

Compared to an open differential, the RS1.5 sends more drive to the wheel that has traction. That means:

• More forward drive out of corners
• Reduced wheelspin in low-grip surfaces
• Better acceleration when exiting tight turns

This is especially helpful in AWD cars where balanced traction front-to-rear matters.

🏁 2. Improved Turn-In and Corner Response

The RS1.5 has a moderate lock bias that:

• Helps the front end bite during turn-in
• Reduces understeer in higher speed sweeping corners
• Makes steering feel more predictable as throttle is applied

Drivers often feel the car rotates more naturally instead of washing wide.

🎯 3. Smooth, Predictable Engagement

Compared to very aggressive LSDs:

• The RS1.5 is not overly harsh on grip break-away
• It doesn’t “snap” when the diff locks or unlocks
• It suits street use and mild track use

This makes it a popular all-around choice.

⚙️ 4. Mechanical (No Electronics Required)

Unlike electronic torque vectoring systems or complex controllers:

• The RS1.5 works purely mechanically
• No complicated calibrations or ECU mods needed
• Installation is straightforward with normal diff oil

This simplicity helps with reliability and long-term maintenance.

🏎️ 5. Front-End Balance for AWD

On cars like GDB(C)/GRB/GVB:

• The factory center and rear diffs often have good lock
• Adding a front LSD helps balance front grip to match the rear/center

Balanced diffs = better overall AWD performance.

🚗 6. Good for Mixed Use

If you’re doing a mix of:

• Daily driving
• Occasional track days
• Rally-style or back-road driving

The RS1.5 sits in a comfortable zone between mild and aggressive LSD behavior.

📌 Who It’s Best For

✔ Enthusiasts who want better traction than stock

✔ People who drive spiritedly but still want street comfort

✔ Cars that see both street and occasional track or rally use

🧠 Notes on Pairing

To get the most from an LSD:

• Use the correct differential oil (Cusco or weight they recommend)
• Pair with good tires
• Performance gains are more noticeable with more power