'87 GMC rear brakes.

[Brownsquare]

One of the many areas in need of attention on my '87 Sierra 1500 is the rear brakes. Last year I pulled the rear drums to see what kind of shape things were in. One side came off easy, but the other was a real fight. I assumed it was because it had been adjusted too tight. Anyway, I took everything off, cleaned and painted the backing plate, installed a new cylinder, and put on new shoes and hardware.

When I went to install the still serviceable drum, neither side would fit. Even when I turned the adjuster down as far as it would go the drum still wouldn't fit. Off to the auto parts store I go to make sure I got the right brake shoes. They send me home with a different set and I swap everything out. Drums still won't go on. I thought maybe the emergency brake cable was hanging up, but nope, seems OK. I go back to the parts store and get a new set of drums. Go home and the ones they gave me WILL go on, but they're too wide...the drum bottoms out on the backing plate LONG before the drum tightens against the axle. WTF?

So I go back to the parts store to check the drums. Get sent home with a different set that look more like the used ones I took off. Go to try them and...won't go on just like my originals. Long story a bit shorter I spent hours trying different combinations in the hope that I'll get something that works. Nope. So I go back and return everything, completely frustrated.

I spoke with a friend later on, who has worked at a Chev dealer for 40 years, and he told me sometimes they had to machine drums to fit the application. That one really threw me for a loop. In all my years of working on drum brake vehicles, I've never had this issue. Starting to wonder if my truck is cobbled from pieces or???

Any ideas guys? Honestly this is just one in a string of struggles I'm having with this thing. Just about to sell it and start over!

[geezer#99]

Post a pic of your brakes with the drum off.
A visual might help us.

[Dead Parrot]

Did the new brake cylinders match the old ones? For many years of these trucks there were 'light duty' and 'heavy duty' brakes. Often based on the GVW but sometimes based on what the original buyer ordered from the factory. Fairly common for a PO to install heavy duty parts on a light duty setup in search of better braking. IIRC, the heavy duty parts are wider then the light duty versions, may explain your bottoming issue with one of the drum sets.

Make sure the pistons are fully seated in the new cylinders. If they have been pushed out, could be your problem. While the adjustment is at the bottom, the action during braking happens at the top.

[Brownsquare]

Hang with me, it's been about 6 months since I last touched this project. The cylinders appeared the same other than where the line goes in. Thanks for the tip on the pistons...they did seem to want to fall out. I wonder if they gave me HD cylinders?

Here's the other difficult part. When I took this whole mess apart, the shoes and hardware appeared to have been recently replaced. Due to how tight everything was, I wonder if the stuff it came with was even correct. I'm at a point where I'd happily spend the cash on a rear disc conversion if I had it! Haha.

I'll have to get some pictures of everything. Thanks guys!

[Just call me Sean]

I put an 83 rear in my 92 G20. The drums and backing plates are different between the two. The 92 drums will fit with the 83 backing plates but not vice versa. So maybe you need a different year drum.

[Dead Parrot]

Originally Posted by Brownsquare

...

Here's the other difficult part. When I took this whole mess apart, the shoes and hardware appeared to have been recently replaced. Due to how tight everything was, I wonder if the stuff it came with was even correct. I'm at a point where I'd happily spend the cash on a rear disc conversion if I had it! Haha.

...

Fairly common for a drum to be hard to get off as the shoes are normally really close to the drums. If the drum is badly worn with a ridge on the edge, they can be almost impossible to get off without a lot of work and aggravation.

[Brownsquare]

Did a little detective work last night. My rear drums measure 11" exactly, so it would appear I have the light duty units, which coincides perfectly with the 1" thick rotors up front. No idea if somebody slipped me some larger diameter shoes, or the wrong cylinders or??? I decided to start from scratch and source EVERYTHING from LMC truck. That way I don't have a weird combination of stuff from different local auto parts stores. I'm not going to let this thing beat me!

Dead Parrot, when I got the truck the brakes on the PS rear were locked so tight you couldn't push the truck in neutral. When I pulled them apart, everything was fresh, drums and all. No ridges. No idea what somebody cobbled together, but I'm starting new.