JB5 rear drum brakes, help getting them to work properly

[navyboy65]

Ok guys my 1994 K1500 has the great jb5 brakes, that's the 10" rear drums. My issue with them is getting them adjusted properly. I have tried many times and have many new parts but still I can't get them to work and allow me to use my parking brake that will hold them truck on a hill? Gone through the steps in the GM manual and have a brake measuring tool it suggests.
My prob is that when I get them adjusted and where the parking brake will hold the truck on a hill I check the drums with the rear in the air and spin, but its mostly smooth but then at times I can here it rubbing, say out of a 360 degree rotation I get 45-90 degrees worth of rubbing each side? I have replaced the rear wheel bearings and notice I still have a little play which I think is due to some wear on the axle shafts where they meet the bearings. Could that be causing my issue?

recently replace items,
Shoes
all 3 parking brake cables
2 new drums
1 new wheel cylinder
drum brake spring kit

Adjusters seem fine and lubed the threads
Truck specifics;
1994 K1500 Extended cab JB5 brake system, 350, manual trans, 10 bolt rear end, z71 but non-heavy duty(that why the small brakes and small rear end)

 

[IOWNJUNK]

Being able to hear the rear brakes drag a little is normal. Once you get them where they just drag the self adjusters on the bottom of the shoes will do the rest.

 

[navyboy65]

Let me rephrase. When I get the brakes adjusted and then adjust the parking brake so that it will hold my truck on a hill I have quite a bit of brake drag and it is not consistant. Rubs more in some spot than others during rotation. I would think similar to out of round drums but these are brand new NAPA drums (unless they were made/machined wrong). Also the brake hardware on the JB5's is different from the JB6&7, JB5's have the adjusters up just below the wheel cylinder.

 

[IOWNJUNK]

I definitely read that wrong......

If you are rubbing in one spot on the drum and not another then I would say an out of round drum. I would assume it would be perfectly round if its new, but you never know. The only way to be sure would be to remove and measure the diameter in several places.

Also, how much drag is quite a bit? Does drum get too hot to touch when you drive?

 

[navyboy65]

I definitely read that wrong......

If you are rubbing in one spot on the drum and not another then I would say an out of round drum. I would assume it would be perfectly round if its new, but you never know. The only way to be sure would be to remove and measure the diameter in several places.

Also, how much drag is quite a bit? Does drum get too hot to touch when you drive?

I have measured both of them several times and the drums feel pretty close to true. I would think that unless they were warped, it would be good enough.
On this set of drums I have not driven enough to get them hot. But last night I adjusted the parking brake so that it would hold the truck on my drive way and when I jacked the truck up to check for drag I had a hard time turning the wheels. I loosened the adjusters down to as close to no drag as possible but now when I brake way less braking from the rear and the p-brake won't hold the truck at all.
Either adjusted to make the service brake work or the parking brake is get spotty drag, again like out of round but I am wondering if worn axles could also cause this?

I will be messing with these brakes again tomorrow, and will try to measure the drums looking for out of round but my tool isn't very accurate for that. I also will try to measure the axle to see how much end play I maybe getting?

 

[michael hurd]

Out of round drums, possibly from improper storage. After a few heat cycles - ( warming up, cooling down ) the drum should become stable. Take a very light cut out of the drum and re-install. Also, make sure the face of the axle flange is CLEAN... use a wire wheel or like tool to scrub any rust away, as well clean the backside of the rim. Lightly lubricate the wheel studs, torque the wheel properly with a torque wrench.

One thing that most people overlook when installing rear shoes is to see if the backing plate has a groove worn in it at the shoe contact points. This needs to be flat and lubricated for the shoes to work properly, or the shoe will hang up.

Also, you won't get proper braking until the drums and shoes have seated, and you get a transfer of pad material onto the drum, this layer of resin becomes sticky with heat and gives you better braking. If the shoes have an improper curvature in them, it could take a month or so of driving for the shoes to wear to the curvature of the drum. ( IE: you may not have proper contact )

Napa may replace the drums for you, but you may have the same issue: if they turn drums there, see if they will 'goodwill' taking a light cut out of them for you at no charge. Hope that helps!

Here's a handy link as well: http://www.agcoauto.com/content/news/p2_articleid/187

Edit: Re-read your post, there is a possibility the drum is perfectly round if you measure the diameter in several places, yet the center may not be concentric. A light cut out of it to true it up should fix that issue.

 

[IOWNJUNK]

Where are you adjusting your parking brake? On the cable or the star wheel?

 

[navyboy65]

Out of round drums, possibly from improper storage. After a few heat cycles - ( warming up, cooling down ) the drum should become stable. Take a very light cut out of the drum and re-install. Also, make sure the face of the axle flange is CLEAN... use a wire wheel or like tool to scrub any rust away, as well clean the backside of the rim. Lightly lubricate the wheel studs, torque the wheel properly with a torque wrench.

One thing that most people overlook when installing rear shoes is to see if the backing plate has a groove worn in it at the shoe contact points. This needs to be flat and lubricated for the shoes to work properly, or the shoe will hang up.

Also, you won't get proper braking until the drums and shoes have seated, and you get a transfer of pad material onto the drum, this layer of resin becomes sticky with heat and gives you better braking. If the shoes have an improper curvature in them, it could take a month or so of driving for the shoes to wear to the curvature of the drum. ( IE: you may not have proper contact )

Napa may replace the drums for you, but you may have the same issue: if they turn drums there, see if they will 'goodwill' taking a light cut out of them for you at no charge. Hope that helps!

Here's a handy link as well: http://www.agcoauto.com/content/news/p2_articleid/187

Edit: Re-read your post, there is a possibility the drum is perfectly round if you measure the diameter in several places, yet the center may not be concentric. A light cut out of it to true it up should fix that issue.

Ok so might be the drums. We'll see what napa will do, Bought the drums at another store than the one that is near by and I am not sure the local store here turns rotors & drums but I guess I am going to find out next weekend when they are open!
As for the backing plate contacts I think they were pretty clean, maybe a slight ware spot but I did wipe them down and lube them up before assembly. I will check them again as well as the hub surface too!

Where are you adjusting your parking brake? On the cable or the star wheel?

I have done both, adjusted the adjuster/star first and then adjust the parking.

 

[navyboy65]

OK I mess with them some more but have not taken it for a drive to see the results yet.
What I did was use the measure tool to try and get that .01-.02 clearance the manual says to shoot for. I am not sure where on the shoes one is looking for this clearance(I would guess @ 9 & 3 like the manual shoes the tool usage) but the tightest spot for me was when I hold the tool to the drums at the 11 & 5 o'clock positions on drivers side and 1 & 7 on the passenger. So I shot for that .01-.02" less than the tightest spot I found on the drums.
I also cleaned up the hub surface on the axle and the edge. I use a dial indicator to try and measure end play on the axles and came up with .01-.011 drivers and .023 passenger, but there is still some rusty stuff on the edge that may be adding a little. Couldn't find anything in the manuals that addressed end play on axles?
Double checked the backing plates and didn't see any wear spots, used a fine tip tool across the surfaces and didn't feel anything. I had used some syn brake grease on the surfaces during assembly by I can't get that brush in there with out getting it all over everything so I used white lithium grease as that it was the manual says to used. I lubed up each contact point and slid the shoes up and down till the moved smoothly.
Then per the manual I adjusted the brake cables @ the cable equalizer till the parking brake levers just slightly moved off the shoe web stops (pain to see as there is a little hole in each of the backing plates right where the two meet but getting in position and getting light in there to see it hard I had to use my (gun) bore light to get in there). The manual calls for you to then turn back the adjusters to get the parking levers to touch the stops again but I only did that on the drivers side and was like 1 notch on the star/adjuster nut. The pass side seemed fine.
With all this done the wheels/drums turn pretty easy with just a little rub during rotation.

Thanks for the help guys, it is great to get help from those who know more/better and to bounce ideas off.
I'll update after a drive & some miles, as maybe I won't need to turn the drums, at least that is my hope!