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Towing obviously stresses the brakes more and the disc brakes will dissipate heat better, if I towed anything heavy the extra maintenance for rear disc brakes would be worth the work. I drove a wrecker with 4 wheel drums for about a decade, hot drum brakes won't stop.As many have noted, maintenance is a key - I swap summer tires for winters twice a year and check that everything is working on the brakes at each change. I also have the Snap-on large 3 jaw puller which when used with 1/2" impact (vibration helps loosen) has resulted in all that have come before it submitting.
@19Walt93: We can vigorously discuss whether the rear brakes are doing anything or not when I'm going down a grade while towing the 5th wheel to the point where disc are an advantage. Remember, I consider my Ranger a truck and use it as such.
Forgot to mention about the '72: the reason the front drums were a pain to replace is that the wheel spindle/hub/grease cap is smack in the way in the middle. You had to work around it to change the shoes. Front discs are generally far easier.I've worked on both disc and drum brakes many a time. Straight disc brakes without a drum parking brake are generally a bit simpler to work on.
Many vehicles kept rear drum brakes for cost and also because the front brakes do 80% of the braking anyway. On most cars it doesn't make much difference what type the rear brakes are. Trucks that haul heavy loads or pull trailers are exceptions.
My late stepfather's '72 F-100 pickup (last year for that body) still had front drum brakes. It did not have power assist for the brakes, either, so the master cylinder didn't have the big power booster. I replaced the shoes on all four wheels. The fronts were a pain. For '73 with the new body front discs were standard.