Those are the JB5's. Check the RPO codes in the glove box.
There has been much discussion on the bad brakes of the 1988-1998 body style.
The rear drum brake adjusters do not work properly, and many find themselves having to manually adjust them every thousand miles or so in order to get the rears to work properly, or they have to cut holes in parts in order to do that as the JB5s do not come with a way to easily adjust the brakes.
You can convert to the JB6 rear brakes, but even that is not a bolt-on. It requires that the rear end be modified as the backing plates on the JB5 set has a rectangular pattern and the JB6 has a larger square pattern.
An alternative would be a new rear end from a truck that already has the JB6 brakes. The JB6 adjusters will work as they should, which will keep the rears adjusted properly.
**BUT**, the JB6 drums & axles are 6 bolt.
Band-aids to avoid the large part replacement include stainless flex lines and DOT-4 brake fluid. The stainless flex lines will work wonders for your brakes, it will make your truck stop like other cars do, like within a reasonably safe distance, and the DOT-4 fluid can handle higher temps, which reduces fading.
Super lube the self adjuster with anti seize on the treads, both male and female. Be careful not to use too much. The key is to have the adjuster star wheel turn freely and why I always use liberal (enough without dripping onto the braking surface) amounts of anti-seize on both male/female portions of the star wheel. Plus the star wheel itself. (female cavity that goes onto the post of the threaded part).
JB5's are archaic and a dumb design. I find the teeth on the adjusters to be far apart which might contribute to the mushy feeling. Too much wear/gap needed before the next tooth is engaged.
The JB5's can be modified by drilling the drum's hat section.
Drilling a hole in the drum hat section will allow you to tighten them even more than what the adjusters will do on their own. Just note that the shoe will wear out faster, but that's a good thing, since now they are doing some real work.
That hole needs to be big enough and aligned to the adjuster wheel. 1/2" works. Then it can be manually adjusted from the wheel side. The backing plate side has the axle tube and flange in the way.
Measure from the center of the hub to about where you want the 1/2" dia hole to be over that adjustment wheel.
Then put the drum back on and remeasure for the center punch.
If you have alloys, consider it lucky if this new hole lines up with one of the openings so that you won't have to remove a wheel to manually adjust them.
Then add rear shoe wear inspection for each oil change and have a spare set of shoes ready.
