Time to do the rear drums-a few questions

[pritch]

Time has come to rebuild my rear drums on my C10 Panel, but I have a few questions.

I have 11" drums and 2" wide shoes-I've read that there are some drums that take 2 3/4" shoes. What is the difference, besides the obvious? Is bigger better? Is it worth the trouble to track down these drums? My existing rear drums are OE, as far as I can tell, that seem to have been turned once. I also have a new set that came off the front that only have maybe 3000 miles on them, so I have that option also.

Wheel cylinders. I have no problem rebuilding the ones I have, but they have a 1" bore, and again-is bigger better? I see there are some with larger diameter bores.

I guess my overall question is-If I use rear drums, what is the best combo of parts to use?

Does that make sense? I'm not talking about mix & match, more like is there a better set up from another truck that might be better on my Panel that OE?

[Sammy]

Someone will correct me if i am wrong. But the trucks came with two different widths of drums. I believe that was an option J56 heavy duty brakes. As cheap as wheel Cyl, are very few use rebuild kits on them anymore. The hassel of honing and all is time consuming. Good luck.

[Smallz72project]

Howdy. I will try my best to help and lend advise as much as possible. I work for Les Schwab and am a certified brake technician. There are definetely pros to having larger brakes...better braking better heat dissapation. But that normally is in terms of overall diameter, 10" opposed to 11". The difference in shoe width is probably due to compensate for a heavier suspension/ wider stance. However the differences are not just in the shoes....the drums will be different all together. Im not real knowledgable on the panels, but Im sure the backing plate sits further back from the axle flange on the 2 3/4" brakes opposed to the 2". So there is a possibility the axle shafts are different lengths...meaning those would have to be changed if not also the backing plate. All the hardware (hold down springs) are probably set up different for the two as well. As far as the wheel cylinders go....a one inch bore can exhert more force on the brakes but you have to take into consideration what your master cylinder is doing. That one inch bore is going to take more fluid meaning your mastercylinder is going to have to do more work (pedal travles farther to do the same amount of work as a smaller bore), making the pedal feel less firm and more spongy. Sorry this isnt the exact answer you were looking for, just hope I was able to give you some more insight and points of view to go from.

[vectorit]

Your 11" drum brakes are no big deal as far as parts go, and there is nothing special about them being that they belong to an axle under a panel/burb.

You can get everything you need for those at a Napa store, and I would buy everything in them. New shoes of course, new wheel cylinders, new spring kits, and new rubber brake line. Since yours I bet is probably the original.

There are multiple "Spring kits" so be sure to get the one called "Spring kit", and the one called "Self adjuster spring kit" for both left and right sides. You will also get a new adjuster arm, and self adjuster spreader. (Make sure you don't mix those up, since each side is threaded differently - Counter clockwise and clockwise thread).

All those parts won't be that expensive, so don't skimp on them by rebuilding the WC's and re using the springs.

I'd probably go as far as replacing the axle seal if it's never been done, but if they are dry and look good then move on without doing them I guess. Since you could open a new can of worms.

Since you are getting a basket load of parts at the local Napa. I recomend getting some rubber work gloves, brake cleaner, a small disposable scrub brush, a can of black paint, and a can of white lithium grease to lube the contact points and E-brake cable inside the drum. Oh, and buy plenty of new DOT-3 brake fluid so that you can flush out as much of the old muddy brake fluid in there for sure.

Oh, and if it were me... I would replace what you have like for like and not try to upgrade anything. Why gamble with your brakes?

[truckdude239]

i'd just go back factory wheel cylinders are cheap just buy new ones hardly anyone rebuilds them anymoreif i remenber correcty the front drums are diffrent then the rear someone please correct me if i am wrong

[pritch]

Good points made. I think I'll stick with what I have. I was always planning on getting new stuff no matter which way I decided to go, except I think I'll get my existing drums turned-there's still plenty of meat left there. As far as axle seals, my rear end () is at the shop this very minute getting rebuilt, and I have all new brake lines. I'll rebuild/restore most things, but like the man said-why take chances with the brakes? That's why I went with discs in the front in the first place. As far as the front and rear drums interchanging, all I know is that they are the same part # in the LMC cat. I know that's not always 100% correct, so who knows.

Thanks for the replies.

[Zeke]

I upgraded the rear brakes on my 69 using the following parts:

Backing plates 1981 GMC 2wd 11x2 3/4 w/wheel cyls: free
New shoes 1981 GMC 2wd (JB5 brake sys): 39.98 Advance
Hardware kit: 6.38 Advance
Rear drums 1981 GMC 4wd (six lug): 29.97 (60.00) Autozone #8846

Everything was bolt on and just had to bend the brake line a little to hook up the wheel cylinders.

Hollander's shows the following 2wd had the big rear brakes:

Blazer 76-82 4x2
Chev Tr. 73-74, fwd cont., 10 ser
Chev Tr. 73-87, conv cab, 10 ser
Chev van 74-89, 20 ser
Chev Tr. 75-80 fwd cont., 10 ser
Chev van 78-89, 10 ser
Chev Tr. 88 conv cab, 10 ser
Chev Tr. 89, conv. cab, 1500 ser, VIN R/V
GMC Tr. 73-74, fwd cont,1500 ser
GMC Tr. 73-87, conv cab, 1500 ser
GMC van 74-89, 2500 ser
GMC Tr. 75-80 fwd cont., 1500 ser
GMC van 78-89, 10 ser
GMC Tr. 88-89 conv cab, 1500 ser, VIN R/V
Jimmy 76-82 4x2

It has been serveral years since I did this so the prices might be a little dated.

It was well worth the upgrade and I can tell the difference especially when hauling a load. The backing plates allow you to put the bigger brakes on.

[lo72]

Did the same swap to my 70 c-10...used the parts off of a 90 suburban..it all bolted on ..simple as a rear brake job!!!