Please Help My Drum Brakes are Locking Up When Backing Up a Hill
Updated 10/22/2025 | Published 04/11/2025
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Question:
I put all new drum brakes on my trailer as well as this replacement master cylinder. I’m having trouble with the trailer braking while I back up a hill. I know disk brakes need a reverse solenoid, but I thought drum brakes had a free backing design. Could I have messed something up in the installation?
asked by: Kirby G
Expert Reply:
Hello Kirby,
I am sorry to hear you are having issues with your brakes acting up when you are reversing up a hill. If your trailer brakes are locking up when you back up a hill, even after installing new drum brakes and a new master cylinder, there are a few things that could be going on. Most drum brakes these days are “free-backing,” which means they’re designed to let you back up without the brakes grabbing. But that only works if you got the right kind and installed them the right way. It’s worth double-checking that the brakes you bought are actually free-backing. Also, each brake assembly is made for a specific side if you accidentally swapped them left to right, or installed the shoes backward (the shorter shoe should face the front), they might not work properly in reverse. If you could give me a part number I am happy to make sure they are free backing brakes.
Another thing to look at is the master cylinder or actuator you installed. Even with drum brakes, if you’re backing uphill, the surge coupler might be compressing just enough to apply the brakes. Some master cylinders are built to hold a little pressure in the lines, and that can cause issues when backing up. If your actuator has a spot for a reverse solenoid (basically a valve that stops brake pressure when you’re in reverse), you might want to add one especially if you're regularly backing up hills or driveways, the Replacement Solenoid Valve for Dexter Brake Actuators with Reverse Lockouts # T4748800 will do the trick. A quick test: jack up the trailer, spin the wheels by hand, and see if they lock up when you move the actuator in reverse. That’ll tell you if it’s a mechanical issue.
Please let me know what you find out.
Product Page this Question was Asked From
Replacement Master Cylinder Assembly for Dexter Model 10 and Model 20 Brake Actuators - Drum
- Accessories and Parts
- Brake Actuator
- Hydraulic Drum Brakes
- Master Cylinder
- Dexter
more information >
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Kate F.
10/22/2025
Hey Kirby, what did you find when you tested the trailer brakes after checking the shoe orientation and the master cylinder? Knowing whether the solenoid valve helped with backing up the hill could really help others running into the same issue.