NEED HELP!! 1973 Dually Brake Problems

[Crcrft78]

Does anyone have a part # for the rear brake wheel cylinders? I have tried 3 sets and the first two where 1/4 inch too wide and wouldn't fit without me grinding on the bracket attached to the backing plate. The 3rd set was the correct width but the threads for the brake line were 7/16-24 and my brake line has a 3/8-24 fitting. The auto parts stores all list wheel cylinders for every year except 1973. It seems like that is a problem year for parts. Maybe because of the model change I don't know. Any help would be appreciated.

[Woodyboat]

Can you modify one of the sets available to fit?

That was my first question, here's my second. Because 73 was the first year for the square body, do you suppose the wheel cylinders from a 72 would be correct? I mean, true they're different body styles, but maybe it's a possibility that parts were continued until the assembly line ran out - especially if your truck was somehow built very early in 73. I've heard of manufacturers doing that before but I don't know if GM was one of them.

Years ago, I had a 1970 F100 Ford. It was something of an ugly step child year for Ford because of a huge UAW strike and production numbers were way way down that year. There were a lot of trucks running around on the road that looked like mine but all were either earlier or later - but never another 1970. Many times, I found the part I was looking for would be from a 1969 and other times from a 71 or 72. That's what made me think of this. But that was Ford and who knows how THEY dealt with things...

I also ran into the same problems with an old Harley. It was one of the very first Evolution bikes and many parts were from the old Shovels.

[Crcrft78]

So far I have tried 4 sets of wheel cylinders and there is something wrong with all of them. They're either too wide or the thread size for the brake line fitting is wrong. I have one last set to try from Raybestos and if those don't work then it looks like my only option is using the wheel cylinders that fit and changing the brakes lines to match.

I think it has something to do with 1973 being the first model year for a squarebody. All of the local auto parts stores list wheel cylinders up to 1972, skip 1973 and then resume at 1974. All of the wheel cylinders I've tried say they should work on 1967-72 then 1974-up and don't work on 1973. I even cross referenced the part # on the wheel cylinder I took off and the compatible wheel cylinder that matches it doesn't fit either go figure.

[Woodyboat]

That's crazy!

Are your old wheel cylinders rebuildable?

[cadillac_al]

You should be able to get adapters from 7/16 to 3/8.

[daddyjeep]

I would just bend up some new brake lines. I'm sure it would take a lot less time to make new lines than it would to go to the parts store again.

[Crcrft78]

The whole purpose is to try and find an over the counter replacement without the hassle of adapters or new brake lines. Which so far is not happening. I'm not opposed to using the adapters or bending up new brake lines. Is it time consuming, yes. So is expending the time to post this on the forum but I thought it might help others if they come across this issue and someone finds the correct part number to fix this. There are two more sets of wheel cylinders I will try and if they don't fix the problem then I will move forward and try some of your other suggestions.

[Woodyboat]

Well, at least you know that we are feeling your pain.

I think I really like daddyjeep's idea and I would carry it a little farther. I would little by little just bring everything else up to 1974 specs.

[Robert1970C20rstbukt]

I found these in the 73-78 Chevy truck parts book, they sure did use a lot of different part numbers back then for the C30 wheel cylinders. These numbers were the only ones I found for a '73 only.

1973 C30 exc. 11,000lb axle, also shows to fit 1960-1972 C20/K20-C30 trucks in the interchange on the Dorman site.

5457162 LH side 1 1/8", Dorman # W35325
5463031 RH side 1 1/8", Dorman # W35326

[Crcrft78]

I found these in the 73-78 Chevy truck parts book, they sure did use a lot of different part numbers back then for the C30 wheel cylinders. These numbers were the only ones I found for a '73 only.

1973 C30 exc. 11,000lb axle, also shows to fit 1960-1972 C20/K20-C30 trucks in the interchange on the Dorman site.

5457162 LH side 1 1/8", Dorman # W35325
5463031 RH side 1 1/8", Dorman # W35326

That was the first set I tried. 1/4 too wide on my truck.

[slotard]

How different are the dually brakes than the SRW 14FF? I have an SRW axle that I'm converting to discs and you're welcome to any of the leftover parts I have. Off a '75 I think... then it's going under my '73, at which point that axle will be available. I don't feel like pulling the drums off the '73 before I swap it out though.

[Robert1970C20rstbukt]

Does your truck have a Dana 70 axle or a GM 14 bolt? I checked the book again and also found these, listed for a 1973 C30 with dual wheels. These are listed as having a 1" bore and 3/8"-24 inlet threads:

18005633 LH side 13" x 3 1/2" brakes, Dorman #W13387
5465038 RH side 13" x 3 1/2" brakes, Dorman #W13388

[Crcrft78]

It has a Dana 70 axle. The rear brake shoes I pulled off measure 13" x 2 1/2" and the wheel cylinders I took off measure 1 1/8" bore with a 3/8"-24 inlet thread. So far I have tried the following wheel cylinders:

5457162 LH side 1 1/8", Dorman # W35325
5463031 RH side 1 1/8", Dorman # W35326
Correct size for the bore and inlet thread but a 1/4" too wide and won't fit between the bracket on the backing plate.

I have also tried WC34475, WC34474, WC14493 & WC14494 From O'Reilly Auto Parts. Also wrong. Either too wide or wrong inlet thread.

18005633 LH side 13" x 3 1/2" brakes, Dorman #W13387
5465038 RH side 13" x 3 1/2" brakes, Dorman #W13388
These are next on my list to try.

ACDELCO 18E1124 {#18E443, 19175653, 89052213}
Rear Left; with 13 in x 3-1/2 in Brakes
ACDELCO 18E1123 {#18E444, 19175652, 89052214}
Rear Right; with 13 in x 3-1/2 in Brakes
These are also next on my list to try.

Maybe I will get lucky and find a set of wheel cylinders that work from the two listed above.

[Crcrft78]

How different are the dually brakes than the SRW 14FF? I have an SRW axle that I'm converting to discs and you're welcome to any of the leftover parts I have. Off a '75 I think... then it's going under my '73, at which point that axle will be available. I don't feel like pulling the drums off the '73 before I swap it out though.

At this point I will try anything if I can't find the correct wheel cylinders. The ones that came off the truck need to be honed because they leaked pretty bad and have some corrosion inside the bore before I attempt to rebuild those and try them.

[Crcrft78]

Well I have FINALLY found a wheel cylinder that fits thanks to Robert1970C20rstbukt and the information he provided.

18005633 LH side 13" x 3 1/2" brakes, Dorman #W13387
5465038 RH side 13" x 3 1/2" brakes, Dorman #W13388

The passenger side went right on without any hassle. I can check the driver side once the passenger side is together. I'm not sure what the problem was or why all the auto parts stores came up with other parts #s and never this one. I am sure it has to do with the different rearend axle options are trucks came with. Anyhow, the above part # provided by Robert1970C20rstbukt fits the Dana 70 axle.

[lolife99]

Thanks for reporting back with the correct part numbers.
This will help more people in the future.

[Robert1970C20rstbukt]

Good deal, glad I could help. I'm betting it had to do with changing over from the old body style and drive trains to the new. Guess they made a typo on the brake shoe size if the ones on your truck were 13" x 2 1/2". From 1973 to 1978 it showed four or five different wheel cylinders for a C30 truck, one part number shows to fit either side of DRW trucks from 1974 up to about 2004.

[Crcrft78]

Uh oh. Now that we solved the wheel cylinder mystery, I have a question about the rear brake drums. Of course, the auto parts stores list nothing for a 73, but a 74 now those parts they have in stock. So I am wondering, my dually has the 2.5 inch rear brake shoes and the brake drum has a mating surface of 3 inches. 1974 rear brake drums show a 3.5 rear brake shoe with a 4 inch mating surface. Can the bigger drums and brake shoes be put on in place of the narrower shoes and drums or will it create a problem with the axle width? I am only asking this out of curiousity and because my reasoning tells me that a bigger brake shoe mating to a bigger drum should create better braking if the truck already uses smaller equipment. Any thoughts on this?

Also, I was able to locate the rear brake drums for my 73. I just hope they are the correct ones.

[Crcrft78]

Well as luck would have it the part # for the rear brake drums I ordered turned out to be for front disc brake rotors. This after the parts guy called the company in front of me and confirmed they were for rear dually brake drums. So, does anyone have a part # for the drums.

This pretty much sums up how I am feeling trying to get the brakes done on this truck. Am I the only one who has dealt with this much trouble working on a 73 RCD?

[SCOTI]

What p/n is listed for a 72 C30?

I would seek my parts based on the known 'carry-over' philosophy GM has maintained over the years. Since your's is a first year model, if things don't match, go back to the previous year model & see what happens.

[Crcrft78]

The P/N for the 73 rear brake drums matched a 72 C30 according to the parts guy. He even called the company in front of me to confirm the order. I asked this because of what I dealt with with the wheel cylinders. They have 74 brake drums on the shelf but they call for 3.5 inch brake shoes while my 73 has 2.5 inch brake shoes. So I am wondering, can the bigger drums and brake shoes be put on in place of the narrower shoes and drums or will it create a problem with the axle width?

[SCOTI]

Originally Posted by Crcrft78

The P/N for the 73 rear brake drums matched a 72 C30 according to the parts guy. He even called the company in front of me to confirm the order. I asked this because of what I dealt with with the wheel cylinders. They have 74 brake drums on the shelf but they call for 3.5 inch brake shoes while my 73 has 2.5 inch brake shoes. So I am wondering, can the bigger drums and brake shoes be put on in place of the narrower shoes and drums or will it create a problem with the axle width?

On the 1/2 ton trucks, the wider brakes require different backing plates. I'm betting the larger trucks are no different & you'll need to stick w/the current width vs going wider.

[Crcrft78]

On the 1/2 ton trucks, the wider brakes require different backing plates. I'm betting the larger trucks are no different & you'll need to stick w/the current width vs going wider.

I don't know but this is getting ridiculous trying to do the brakes. I might search the junkyards for a different rearend just to avoid all of this hassle next time. What do they expect those with these years to do if they don't offer the parts.

[Crcrft78]

OK so I am back at it AGAIN with these brakes. Raybestos makes the rear drum (RAYBESTOS 8023R {#108023, 8023, F8023} Professional Grade; Outside Diameter 15.28" / 8 Bolts / Finned Info Rear; Dual Rear Wheels). Rock Auto had them and now they are listing OOS. I have tried dealer listings recommended by Raybestos with no luck.

If any of you happen to be working on your trucks or making a parts run, could you please check in your area if anyone has them available. I could possibly give you a little money for your time if I am able to purchase a set of these drums.

This thing has been sitting in my driveway way too long.

[Crcrft78]

I am at my absolute wits end with this F***ING truck and its brakes. Does ANYONE know for a fact if 74-75 brakes can be bolted up to the 73 without any problems. I'm ready to send this thing to the f***ing scrapper.