Prothane 4-503-BL Transmission Mount Insert Left Black

The Prothane 4-503-BL is a black polyurethane transmission mount insert designed for the left (driver's side) transmission mount position. Specifically engineered for FWD performance applications, this insert fills the engineered voids in the factory OE transmission mount, dramatically reducing unwanted drivetrain movement to improve throttle response and shift feel.

Factory OE transmission mounts are built with open voids to isolate NVH (noise, vibration, and harshness) for everyday driving comfort. While effective for a stock vehicle, these voids allow excessive powertrain movement under hard acceleration, resulting in sluggish power transfer and imprecise shifting. Prothane's polyurethane insert fills those voids to firm up the mount without the cost of a full solid replacement mount.

Key Features:

• Polyurethane construction — far more resistant to heat, oil, and mechanical stress than factory rubber
• Left (driver's side) position — targets the transmission mount specifically for precise drivetrain control
• Black color with graphite additive — same durometer as red Prothane inserts; graphite content helps minimize squeaking
• Drop-in design — inserts into existing OE mount hardware without full mount replacement
• Improves traction and acceleration response by limiting drivetrain flex under load
• Improves shift quality by reducing transmission movement during gear changes
• Lifetime warranty — backed by Prothane's limited lifetime warranty against defects in materials and workmanship

Important Note: These inserts are designed to work with OE mounts that are in good, undamaged condition. They are not a replacement for torn or collapsed rubber mounts. Inspect your existing mount before installation and replace it if worn before fitting these inserts.

Available in red (4-503) or black (4-503-BL). Both colors share the same durometer hardness and performance characteristics.