Mopar J8 Master Cylinder and Brake Booster Kit

If your Jeep Wrangler JK is running heavier wheels and tires, aftermarket axles, or a big brake setup, the factory brake hydraulics can start to feel soft. The Mopar J8 master cylinder and brake booster kit is a proven upgrade that increases hydraulic capacity and boost to deliver a more confident pedal and stronger, more consistent braking.

What this kit helps with

• Firmer brake pedal feel through increased fluid displacement (1.125 inch master cylinder bore)

• Improved brake response for higher braking demand builds, including Dana 60 applications

• OEM parts included in Mopar’s Big Brake Kit (P5160051)

Important notes before you buy

• Jeep Wrangler JK (2007–2018) with automatic transmission

• Automatic transmission only

• Does not fit with underhood ARB twin compressor mount

Installation guidance
Brake system work is safety-critical. Proper bleeding and verification are required after installation. If you are not experienced with brake hydraulics, professional installation is recommended.

Manual Transmission Note (Read Before Ordering): The factory JK manual clutch system normally shares fluid from the brake reservoir. The J8 master cylinder reservoir used with this upgrade does not support the factory clutch feed, which is why this upgrade is commonly listed as automatic transmission only. To run this on a manual transmission JK, you must convert the clutch to a dedicated remote reservoir (mounted in the engine bay) and plumb it to the clutch master cylinder, then bleed the clutch system after installation. This is an installer-level modification and should be performed by an experienced technician. See JK-CLUTCH-MC to order.