GM Service Manual Online
For 1990-2009 cars only

System

Master Cylinder Diameter

Front Disc Brakes

Rear Drum Brakes

Rear Disc Brakes

Brake Assist

JB7

31.8 mm

319 x 39.3 mm

331.5 x 63.8 mm

--

Hydraulic Hydro-Boost

1.25 in

12.50 x 1.54 in

13.00 x 2.50 in

--

JB8

31.8 mm

319 x 39.3 mm

331.5 x 63.8 mm

--

Hydraulic Hydro-Boost

1.25 in

12.50 x 1.54 in

13.00 x 2.50 in

--

JF9

40.0 mm

357 x 36.7 mm

--

346.8 x 36.7 mm

Hydraulic Hydro-Boost

1.57 in

14.00 x 1.44 in

--

13.60 x 1.44 in