Never any need to replace a brake shoe return spring except if a spring is broken. This is very rare. You can verify correct OEM type springs by taking off a rear drum and taking off a front drum. If those springs, front and rear, match, those are original OEM. Odds of someone installing wrong type springs both front and rear are zero; people do not replace brake springs without a good reason.
When we purchased our 48 GMC 3 ton, same problem but right rear. Only needed to drive about 30 miles to get back home, took almost four hours. Every stop, right rear brake would lock up requiring backing up a bit, then taking off again. Here in California, quite the traffic control problem with people constantly tailgating. My girl did a bang up job of jumping down from our cab, waving a tire iron and cussing to get drivers to back up out of our way. She is a Choctaw Indian, looks a bit on the savage side, not sure it was her tire iron which scared people into backing up then taking off in a rush.
Well, there was also a problem with a stuck float and flooding.
Most likely, your shoes are adjusted up a tad bit too tight, or there is severe rust here and there. I doubt you have a rust problem.
A test is what I mention, backing up a bit to discover if a shoe or shoes will back off and free the drum. This is brakes adjusted too tight. This can also be "gummy" shoes.
In our case, brand new linings were installed before we bought the truck, right rear shoes were simply adjusted too tight. Big trucks need more brake shoe to drum clearance than small trucks. You are dealing with a lot of surface area and dealing with brakes which heat up very quickly. This leads to circumstances of a little shoe drag, this is all which is needed to "pull" a shoe into a lock position.
Other problem is gummy shoes. A few drops of brake fluid, someone leaving behind greasy fingerprints on a shoe, add some brake dust and you have a gummy Elmer's Glue spot on a shoe.
Best is to remove your drum, lot of work on a big truck, yes, but removing the drum is a must. Go in have a good look for an obvious problem. None found, air dust out everything really well, wash down your shoes with lacquer thinner, use a small stiff brush to rub in a little hard axle grease at all pivot points and rub points. Grease up your adjustment bolt threads, back off your adjustment a dozen turns or so.
Reinstall your drum, adjust your shoes until there is no doubt the shoes are beginning to rub the drum, then back off your adjustment a good 4 to 8 turns. Deliberately adjust your shoes much looser than you would a small truck. This will cure your problem of brake lockup while there are no other obvious problems.
Concept is after working your brake pedal a few times, your adjustment ends up tighter than what you set. Reason for this is the sheer size of your truck. Brake lines are so long and especially if you have a hydrovac, your return springs cannot quite push all the brake fluid back into your system after braking. There is just enough resistance to keep your shoes spread slightly more than what you adjusted. Your working adjustment ends up too tight, a shoe drags a bit and catches, especially if there is a gummy spot on a shoe.
Keep your big truck brakes a bit on the loose side. You could probably get by without a savage Indian girl riding shotgun.
Billyray
