Having trouble findind brake drums 9.5" 14 bolt.

[NorthernMainer]

Hey guys, so I bought a pair of 3.42 axles to go under my 82 K20. I'm having trouble finding drums for it. The axles came out of another 82 K20

Every drum I look up is wrong, I've checked every possible GM model that could have come with a semi float rear from 1980 to 2000 or so.

My drum measures a hair over 13 outside diameter, a hair over 11" on the braking surface inside, and if I lay the drum flat on my bench, it measures 4.75" wide. So it's technically an 11" drum. The only 11" drums I can find are too wide by quite a bit.

Any help is appreciated. I can find a 13 inch drum that is 4-5/8 wide.. can I swap out the backing plates for 13" and just run those?

The mounting flange for the backing plate is closer than normal to the end of the axle tube if that makes any sense.

 

[Old Guy Bill]

I believe that's an 11 5/32" drum, I forget the width.
Try LMC, that's where I got a set.

 

[xm20k]

If the shoe is 2.75 wide it might be an older rear 73-80

This is the only thing I could find close to that diameter, bolt pattern etc. for a GM truck.

Pardon Our Interruption

 

[NorthernMainer]

I believe that's an 11 5/32" drum, I forget the width.
Try LMC, that's where I got a set.

Unfortunately I've checked every 11-5/32 drum on rockauto, but no luck. They're too wide. Lmc truck doesn't show details on the drums, which I find odd.

 

[NorthernMainer]

If the shoe is 2.75 wide it might be an older rear 73-80

This is the only thing I could find close to that diameter, bolt pattern etc. for a GM truck.

Pardon Our Interruption

I actually tried to look up earlier years, but then I discovered that the semi float didn't start being produced until 80 or 81.

I did find a drum for an 83 k20 or c20 suburban that's 4-5/8" wide, but they're 13 inch. I wonder if I can change to 13 inch backing plates, and use those drums

 

[bucket]

Yeah, I'd just source some backing plates for the 13" drums. I'm not sure why GM ever bothered with those little brakes on a 3/4 ton to begin with.

 

[legopnuematic]

Raybestos 1009R/Centric 123.66012 appears to be what you need. Bad news is they appear to be discontinued.

 

[CalSgt]

Looks like there may be some specs under the paint on the face of the drum. Maybe a part number you could use for cross reference.

 

[NorthernMainer]

Raybestos 1009R/Centric 123.66012 appears to be what you need. Bad news is they appear to be discontinued.

Those are it, I found one on ebay, but it's just one. I guess I'll buy some 13" backing plates, and use a k20 suburban rear drum. They had one that is 4-5/8 wide. It should work.

Thank you for the help.

 

[NorthernMainer]

Looks like there may be some specs under the paint on the face of the drum. Maybe a part number you could use for cross reference.

By paint you mean rust Lol. I tried to get the casting numbers off it, but its just too pitted.

 

[NorthernMainer]

Yeah, I'd just source some backing plates for the 13" drums. I'm not sure why GM ever bothered with those little brakes on a 3/4 ton to begin with.

The suburban used a 13 inch drum thats the right width, so I'm thinking that's the way to go.

 

[NorthernMainer]

Found a solution! A full floater. It's an open diff with 4.10 gear, but I'll slap a trutrac in it with a 3.42 gear. They'll never stop making brake parts for a full float.