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Dorman - First Stop Brake Master Cylinder P/N:M39309
$121.99
Turn brake-pedal pressure into the hydraulic force that operates both brake circuits with the Dorman - First Stop Brake Master Cylinder M39309. It's precision-engineered to match the design, function, and performance of the original master cylinder, dropping in as a direct-fit replacement across a range of 1976-1996 Chevrolet and GMC full-size vans and light trucks (engine: All).
- 100% new: built entirely from new materials, not remanufactured.
- Cast iron housing: constructed to match the casting material of the original part for similar performance.
- Durable design: the rubber components use a high-quality EPDM compound for resistance to glycol-based brake fluid.
- Made to meet rigorous SAE International standards.
The unit has a 34 mm bore, two outlets, and a 1/2-20 secondary outlet thread, and it includes the reservoir. Mounting hardware and a sensor are not included—consult the vehicle service information for the correct fasteners and whether they may be reused. If a leaking or worn master cylinder is behind a sinking or spongy pedal, this replaces it. Country of origin: China.
Manufacturer part number M39309.
Frequently Asked Questions
What does the M39309 master cylinder do?
It converts the force from your brake pedal into hydraulic pressure, sending brake fluid through its two outlets to operate the vehicle's brake circuits.
Does it include a reservoir?
Yes. The reservoir is included with this master cylinder.
Are mounting hardware and a sensor included?
No. Neither mounting hardware nor a sensor is included; consult the vehicle service information for the correct fasteners and whether they may be reused.
What are the key specifications?
It has a cast iron housing, a 34 mm bore, two outlets, and a 1/2-20 secondary outlet thread.
What vehicles does this fit?
It's a direct-fit replacement for select 1976-1996 Chevrolet and GMC C3500, C3500HD, G30, G3500, G35, P30, P3500 and P35 models. See the Buyer's Guide tab for the full list.
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Dorman
Dorman - First Stop Brake Master Cylinder P/N:M39309
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