This is a "how to" adjust 521 drum brakes.
First, find a level place to park the truck. Adjust the front wheel first. they are the easiest.
You do not want the truck to move while you are working on the brakes. Set the parking brake, put the truck in gear. I like how Datsun set up the hand brake so that if you try to drive with the hand brake on, when you shift to first gear, your hand pretty much hits the hand brake handle.
Lets do the left side first. Turn the steering wheel all the way left. This makes it easier to reach the back of the left wheel.
Jack the left wheel and tire off the ground.
Remove the dust cover. If yours are missing, I was able to get new ones at a local Nissan dealer, but that was in 2013.
You can see the star wheel inside the brake backing plate.
I have found an ordinary screwdriver works best on the front wheels.
Stick the screwdriver in the hole, and pry the star wheel DOWN to spread the shoes. the star wheel should turn easy at first, and then get tight, after a while. When the star wheel starts getting tight, try rotate the tire and wheel forward and backwards. If you can rotate the wheel and tire, keep tightening the star wheel, by prying it down. When you cannot turn the wheel and tire, go and step on the brake pedal hard. Try to rotate the tire and wheel again. If you can, pry down on the star wheel some more.
Once you get to where the tire and wheel cannot be turned, loosen the star wheel 10 to 12 clicks. Rotate the wheel. It should spin freely, without drag. A light scraping sound is OK. Put the boot back on, turn the steering wheel straight, lower the left side of the truck.
Jack up the right side, turn the steering wheel hard right, and adjust the right side the same way as the left. The star wheel still turns down to move the brake shoes closer to the drum.
OK, front brakes are adjusted. Block both the front wheels, forward and back.
Release the parking brake, and take the transmission out of gear.
Jack up the rear wheel on one side. Shake the truck a bit, so you know it cannot fall off the jack.
Remove the rear dust cover. This view was taken from in front of the rear tire.
The slot to adjust the rear brakes is slightly forward of the center of the wheel. It is easier to get to from the front of the rear wheel.
It is hard to see the star wheel on the rear. You have to just feel for it, in the hole. For the rear wheels, I use this pry bar.
Another view of the pry bar.
Just like the front wheels, you turn the star wheel down to spread the shoes, until you cannot turn the wheel any more. This is why you have to block both front wheels. The truck can roll, and possibly fall off the jack. After you cannot turn the wheel and tire, loosen the star wheel 10 to 12 clicks. Put the dust cover back on, and do the other side.
Take the truck for a test drive. Brake lightly at first. If the truck pulls to one side or the other, the side the truck pulls to, has the brakes adjusted tighter than the other side. Loosen the star wheel on that side, or tighten the star wheel on the side it pulls away from. If the truck stops in a straight line, without pulling to either side, Do a medium stop, and a few hard stops, AWAY from traffic.
If you have not adjusted the brakes in a while, you will notice the brake pedal higher than it was. If there is a big change you will need to readjust the brakes again, soon.
Driving a 521 without the brakes adjusted will wear out one end of the brake shoes very quickly, and you will have to replace shoes much more often. The brakes also do not work as well, when they are out of adjustment.