Yes, of course you can adjust the rear drum brakes. They should be self adjusting. Every time you back up and apply the brakes they should adjust themselves. If that is not working, look for a small rubber plug on the back of the backing plate. Remove that plug and with a brake adjustment tool, you can adjust the brakes. Search Google for the proper procedure to adjust drum brakes.
Are you asking how to??
I adjusted one just before installing the drum, I had the same question, but they worked great afterward.. dave
To adjust the rear brakes you take off the wheel. Take the 2 Phillips head screws out of the brake drum. Insert two 13mm bolts into the brake drum and turn them clockwise. Tighten the bolts down while tapping the drum on the side with a hammer. After getting the drum off you release the pressure on the parking brake adjuster. Adjust the brakes until the drums go on with a little bit of friction. If the back drum brakes aren't adjusted tight enough the brake pedal wil go down too far.
Disk brakes adjust themselves as they wear. Drum brakes have an automatic adjustment built into the brake system. When you back up and stop they automatically adjust themselves. If you remove the drum you will see the adjustment mechanism.
Only the rear brakes are drum brakes. The front brakes are disc brakes. To answer your question, twist the end wing nut by your drum brake. It tightens and adjusts how much you have to press on your rear brake lever.
I have a 1999 Suburban-JB6 brakes. The drum size is 11"
Check related links below for drum brakes.
Are the rear disc brakes or rear drum brakes? If they are disc brakes, ther is no adjustment. If they are drum brakes, you adjust them by backing up and hitting the brakes. Do it in an empty parking lot. If they are drum style brakes, simply put the van in reverse, and accelerate backwards about 10 feet, and jam on the brakes.. repeat a few times and the auto-adjusters will tension the shoes against the drum properly accounting for the pads thickness, or lack thereof. If they are disc brakes, you have no capability to adjust them without removing the wheels, the calipers, and "shimming" the pads so they are thicker inside the caliper. If your pads are to thick, then you have the wrong pads, and if they are to thin to shim out, and safely stay inside the caliper, then yours pads are worn and needing replacement.
Conventional drum brakes.
drum brakes
Its a bad cylinder spring
Drum brakes.