Reese Neis

So the left rear brake on my 1970 cutlass keeps locking up like if I pull up to a stop sign that one brake grabs hard enough to make it feel like you’re gonna go through the windshield anyone know what would be causing this it’s just going forward haven’t had a problem when in reverse

Vintage Chief

Are the rear brakes drum - which would have been factory? Have you recently had a brake job? Does the parking brake work correctly not too tight and not too loose?

Vintage Chief

Most commonly it's often the parking brake is set too tight. In particular, if you just performed a recent brake job you just need to ensure the parking brake is not set too tight when changing out rear brake components; albeit, the reason my asking about the brake job and parking brake. The CSM describes how to adjust the rear drums - I believe they self-adjust by running in reverse several times. Ensure the anti-rattle spring is not compressed.

Here's a link, but the CSM is your best authority.

https://www.brakebleeder.com/rear-br...p-drum-brakes/

Tedd Thompson

I you somehow got brake fluid on the shoes that will cause the brakes to grab, usually only happened on one side unless you are sloppy on both sides...... Tedd

66luvr

I'm with Tedd. I vote for contaminated brakes. Probably brake fluid, I really can't remember if a leaking grease seal, so grease contaminated brake shoes, cause grabbing, probably not since grease makes things slick not grabby. But still I think contaminated brake shoes.

oldcutlass

Most commonly as stated above there is/was a leaking wheel cylinder and the shoes are contaminated with brake fluid. Another clue would be a low master cylinder. Pull the wheel and drum off and take a look.

Vintage Chief

I’d be in with the brake fluid idea except brakes do work in reverse and forward. They lock up moving forward but not in reverse. If it were brake fluid they should lock up in reverse also. My bet is mechanical.