The Stovebolt Site Forums The Parking Lot Big Bolts Obsolete 15" brake drums..what to do?

Hello, I am trying to figure out what to do with my 73 gmc 7500. The drums for the wedge brakes in back are worn well beyond its limits. The Gunite part number is 2658 which are nla. has anyone ran into this problem and if so, what was your solution? other than finding a newer rear axle with modern s-cam brakes? any advice would be well appreciated!

Brake parts availability is what prompted me to convert my '48 1/2 ton to four wheel disk. You can find wheel cylinders and other parts, but not the drums. And brakes are really important, so...

Not sure about your '73 though. I would think those would still be available. Surely our big bolt guys will know the sources.

two older gentlemen that I have talked to said that auto parts machine shops used to "shim the brake shoes" when replacing the drums was not an option. Im assuming that this meant they would place shim stock underneath the pad of the shoe and then rivet the shoe material over the shim stock.

Hy j_shwanks, could you please tell us the width of your brake shoes and the type of wheels you have? I will be away for the next seventeen days but perhaps someone could use that information to find you some drums.

That would be incredibly unsafe. The thinner the walls of the brake drum get, the more likely it is to heat up causing the brakes to fade. Get it thin enough and it could actually shatter.

I don't doubt some used to do that, but you'd go to jail for doing it now.

Hy j_shwanks, some research has revealed some cross over numbers the actual Gunite p/n I believe is 2658A which crosses to Gm p/n 677290, hope that helps.

they are 6'' wide and the wheels are 5 spoke daytons. I will get the numbers off the spokes later today.

Wedge brakes have always been a problem. Every piece of equipment I ever bought with wedge brakes, I have converted to cam brakes. Figure out what rear you have, and buy a banjo housing with cam brakes and use your third member. Cam brakes are not necessarily more modern. Cam brakes were used back in the 30's. Wedge brakes came out in the 70's for weight savings. It was mostly LTL carriers that specced them because they looked good on paper, but were a failure in the real world. I think the last Gunite number was 2658G.

http://www.accuridewheelendsolution...PartDisplayBRAKE_DRUMS&PartNum=2658A

I had a pallet of them laying around until scrap got so high in 2011. You might call a Wabash National Trailer dealer. They are big with Gunite drums. The numbers off of the spokes won't do any good. They are merely casting numbers for for the wheels. But my recommendation would be to find a banjo housing with cam brakes. I would assume you have an 18.5 Eaton Rear. In the 70's GMC's big market was fleets which explains the Stopmaster brakes. The rear end hosing doesn't necessarily have to come off of GMC.

Yes, it is an 18.5k eaton rear end. I can get a rear end from a local truck salvage yard, with taller gears and cam brakes for (rough estimate) 600-800 with exchange of my current rear end. I wouldn't mind getting the truck to move a little faster, it has 5.73 rear axle ratio and its top speed is 54mph with the wind at my back and going down a steep hill.

Most 7500 GMC were designed for LTL city delivery and thats why they are geared so slow. Faster gears with cam brakes will give your vehicle a whole new outlook on life.

It was a Shawano county (Wisconsin) plow truck in the beginning of its life. I just want it safe and ready for the road. The front brakes are really good and have a lot of meat left on them yet. I located 2 used drums for the back with about 50 thousands of wear on them for 90 bucks a piece (and he resurfaced them) I got one side done and it works great! I just started on the other side and one of the 12 degree wedge assemblies was rusted up pretty bad, I wrecked the spring and the wedge getting it off, but I have a new assembly ordered off of ebay along with a new wheel seal. I just got a couple new light/lens assemblies to put on, new from rims/tires and it will be going in for its inspection

In the Meantime...
LISTEN to Ken!
And aquire a banjo assembly with Cams on it for the NEXT BRAKE JOB, and You will be Ready to go.
regards.
steve sr.

Make sure you keep plenty of grease on the wedges and check them to make sure they are properly working. They are notorious for suddenly sticking and then you have no brakes on that wheel.

What a learning experience wedge brakes have been! I have learned 2 things when dealing with wedge brakes. Lesson number 1: Wedge brakes are very simple to understand and service, I believe that alot of trucks with wedge brake systems were not serviced correctly, they were just inspected and adjusted, but never taken apart during a brake service and cleaned/lubricated. I believe wedge brakes work very well when serviced/adjusted properly. with that being said, Lesson number 2: Wedge brakes are almost extinct. It seems as though the military is about the only one that incorporates wedge brakes into new vehicles, the reasoning for this is that there is no exposed linkage that can be damaged. Overall if the drums I needed were readily available I would stick with wedge brakes, however they are not, so therefore I will be on the lookout for a rear axle in the next couple years. Thank you everyone for the help! I have both sides on the drive axle working like a swiss watch, it will lock up the tires with a full load (5yrds) and stay put when parked at a steep angle!