"tighten the driver's side cable until there's no slack. Then, You adjust the equalizer bracket till brake at both of the wheels are more or less equal. .. "
That makes sense
Re-adjust the calibration of the brake shoe...
That makes sense.
But what do you mean by "expand the mechanism"?
I don't have a photographic memory of the assembly
so I don't know what you mean.

 

OH!!!????
Well!
That's the answer!
Now all I have to do is find an old S-10 axle in a junkyard that isn't rusted junk
and replace the one I have now... Thanks!

 

You might have to make some changes to the master cylinder going to drums. Maybe add a proportioning valve?

 

This is not a S10 problem - Its normal for all vehicles ......

Shoe and drum brakes work this way - they have a primary and secondary brake shoe and when brakes are applied the wheel cylinder moves the top of both shoes out into the drum. As long as the bottom adjuster is set right the shoes contact more of the drum surface as the shoes are set square in the drum.

When parking brake is applied there is a cross bar that contacts the swing arm for the parking brake, it shoves mainly the top portion of only the primary shoe into the drum.
As long as you manually set or the automatic self adjusters adjust the shoes they will be set mostly square in the drum.

When parking brake is set if facing down a incline the shoe is drug forward and more of the shoe contacts the drum creating more drag, if the incline is facing rearward the force rolls the shoe back creating less contact in the drum and mainly just the top edge of the shoe contacts the drum.

Its not the fact that they hold better its the fact that as the main shoes are used for the parking brake and have a self adjuster and as long as it is working the shoes set squarer in the drum. Once out of adjustment braking efficiency is cut way down.

No matter what type of brakes a vehicle has put any vehicle in reverse and set the parking brake a light touch on the throttle and the vehicle backs up, Put the vehicle in drive with parking brake set and it takes a whole lot more throttle to get it to move if it does at all.

It's not a fault or miss engineered its just as I said above just the nature of the beast .....

 

Haha, sorry, this isn't my native language
I've been googling to use the right semantics and here's what I found:
https://www.yourmechanic.com/article...pencer-clayton

On a bottom there is a part with a star adjuster. The adjuster combined with the lever are sort of a lock. While turning that adjuster, the white part expands to both sides and increases a tension on a brake shoe. You have to expand the brake shoe as much as possible, but yet allowing Your disc to fit.
If You leave the big gap in between the shoe and the disc, a part of the cable movement will be spoiled on picking the gap.
Despite these on a pictures look like an auto-adjustable, as far as I remember, the one in my S10 didn't look like to have that feature.

 

Odat, that's a really good explanation, and something I've always noticed when I accidentally left the parking brake on.

Back out of a parking spot, you don't notice it, go to drive forward, and it's like, "what the hell?" lol

 

...I've googled a bit more and here's the assembly of my S10 rear parking brake shoes:



There isn't any sort of self-adjusting regulator. Instead of a star adjuster there is a set of the screw and its liner. They are not numbered on the diagram above, but they are the ones that fit vertically from the bottom. The screw head is flat, and match the shoe end. Once installed, that head would remain still. By turning the liner, You adjust the preliminary tension on a parking brake shoe. The liner itself has a collar with a star adjuster. Underneath there is a flat, metal spring that prevents movement of the liner. And that is all. Here's another photo I've googled (sorry I didn't shot mine own while working on it):



The liner star adjuster is at the right end of a parking brake shoe.
Sorry, but this design is a failure.
While passing annual technical survey, they set Your rear axle on a running rollers and measure the contra-torque created by a parking brake. If it is below limit, then You're rejected. There are no excuses on curbs, uphil/downhill and so on... You just get a record in a national system that You were rejected due to a parking brake slip. Funny... not :P

 

My LAST post was for the shoe & drum only.

First diagram was the self adjuster in the drum rear brake system

Second diagrams are for the new style disk brake rears but the theory is the same as far as drag per incline - forward incline the whole c shoe rolls and more of it contacts - reverse incline and it rolls so that less of the surface contacts.

I will conseed it is a bit of a design flaw but the only way around it is pressure on both sides of the shoe or as in the drum type pressure on both shoes -

However as in all things as soon as the least little bit out of adjustment or wear happens every thing is thrown out of kilter .....

 

Nah, I don't complain on Your posts My intention was to post the design I have in my ride. It differs to the ones with auto adjuster and it slips. Probably in a same way as reported by OP. Thanks for the tip with forward/reverse incline. I'll try that out.

 

You're missing the basic flaw:
With the old style drum brakes you did't need an extra set of brakes at all.
And they worked better.
And they worked both ways.
Stop apologizing for GM:
You're not a corporation.