any B-body sedan from 1977 forward with 11" drums should work--wagons do use a different backing plate flange pattern, as you've reported, and larger bearing, even though they use the same drums.

There are some other vehicles--just go to Rock Auto, look up the 11" drum, and then look at the buyer's guide to see all of the vehicles they were used on.

Example: multiple platforms - all are 5x5 wheel stud pattern - same drum used whether 1/2-20 or M12x1.5 wheel studs

BUICK CENTURION (1971 - 1973)
BUICK ELECTRA (1971 - 1987)
BUICK ESTATE WAGON (1977 - 1989)
BUICK LESABRE (1971 - 1989)
BUICK RIVIERA (1971 - 1978)
BUICK ROADMASTER (1991 - 1996)
CADILLAC 60 SPECIAL 1993
CADILLAC BROUGHAM (1991 - 1992)
CADILLAC DEVILLE 1993
CADILLAC FLEETWOOD (1993 - 1996) - D-body, JM4 brakes only
CHECKER MARATHON (1972 - 1982)
CHECKER TAXICAB (1972 - 1974)
CHEVROLET BEL AIR (1974 - 1975)
CHEVROLET CAPRICE (1974 - 1996)
CHEVROLET IMPALA (1974 - 1985)
OLDSMOBILE 98 (1971 - 1976)
OLDSMOBILE CUSTOM CRUISER (1977 - 1992)
OLDSMOBILE DELTA 88 (1971 - 1985)
PONTIAC BONNEVILLE (1973 - 1981)
PONTIAC CATALINA (1973 - 1981)
PONTIAC GRAND SAFARI (1973 - 1978)
PONTIAC PARISIENNE (1983 - 1986)
PONTIAC SAFARI (1976 - 1989)

This will provide you an expanded search for potential sources for the backing plates--just remember to focus on sedans.

 

Thank you for the information, that helps out a ton. All of the sedans ive seen in junkyards have had the smaller rear brakes. Was there a towing package option that gave these cars bigger brakes.?

 

The real story is that the full-size B-body was down-sized to the A-body platform used from 1973 to 1977--Chevelle 4-door/wagon & Monte Carlo shared the same basic 116" WB frame as 1977 Impala & Caprice and the many variants still produced at the time (Buick/Olds/Pontiac)--down from B-body's 121.5" WB in 1976, as a mass-reduction effort, to help improve fuel economy, as the CAFE standards began their never-ending influence on vehicle design & configuration as manufacturers were looking for ways to meet the standards.

CAFE was a 1975 legislative effort to reduce oil use, following the crude oil "shortage" of the early 70's. With today's relative oil glut it makes one wonder whether CAFE in it's present form is really necessary (sorry to go off topic).

The 9.5" rear drum brakes became the "base" rear fitment as part of this effort. There were also both 7.5" and 8.5" (ring gear diameter) rear axles--the 7.5" axle was also for mass reduction--and typically the lower-power, non tow-pack cars were fitted with the 9.5" brake/7.5" axle combination.

To further confuse things, there were both 4.75" and 5.0" (5x5) wheel stud patterns for brake drums across the 1973 to 1996 time line--but B-body with 11" drums were all 5x5 from 1971, in reality. I do not know if this made any difference in the backing plates for a given (11") drum size.

From 1977 (post-downsizing of B-body) to 1990, the larger brake fitment (11" drum) was ALWAYS fitted to wagons and Caprice police cars (9C1), and used 1/2-20 wheel stud threads with the larger 5x5 wheel stud pattern. Anything fitted with 11" drums had the 5x5 pattern from 1977, which also included the larger wheel center-bore (3.07").

Starting in 1991, with the last update to B-body, all models became 5x5 wheel stud pattern, and wheel studs changed to M12x1.5 thread across the board--9.5" drum, 11" drum, and rear disc.

 

further variations

A body 11" drums - 4.75" stud pattern

BUICK CENTURY (1973 - 1977)
BUICK REGAL (1973 - 1977)
CADILLAC SEVILLE 1976
CHEVROLET CHEVELLE 1973
CHEVROLET EL CAMINO (1976 - 1977)
CHEVROLET LAGUNA (1973 - 1976)
CHEVROLET MALIBU (1973 - 1977)
CHEVROLET MONTE CARLO (1976 - 1977)
GMC SPRINT (1976 - 1977)
OLDSMOBILE CUTLASS (1976 - 1977)
OLDSMOBILE CUTLASS SALON (1976 - 1977)
OLDSMOBILE CUTLASS SUPREME (1976 - 1977)
OLDSMOBILE OMEGA (1976 - 1978)
OLDSMOBILE VISTA CRUISER (1973 - 1975)
PONTIAC GRAND AM (1973 - 1975)
PONTIAC GRAND LEMANS (1975 - 1977)
PONTIAC GRAND PRIX (1976 - 1977)
PONTIAC LEMANS (1973 - 1977)
PONTIAC PHOENIX 1977

Note that this stopped as of 1977, the year of transition of the B-body to it's lighter platform. In 1978, the A-body was replaced by the G-body, which was itself downsized just as had been done with the B-body. From all that I can find, all B-body 11" drums from 1977 forward were 5x5 wheel stud pattern.

9.5" (FINNED) drums used on multiple platforms - all 4.75" stud pattern

B-body applications highlighted
BUICK APOLLO 1975
BUICK CENTURY (1973 - 1981)
BUICK ELECTRA (1977 - 1985)
BUICK ESTATE WAGON (1977 - 1983)
BUICK GRAN SPORT (1965 - 1967)
BUICK GS (1970 - 1972)
BUICK GS 350 (1968 - 1969)
BUICK GS 400 (1968 - 1969)
BUICK GS 455 (1970 - 1972)
BUICK LESABRE (1977 - 1986)
BUICK REGAL (1973 - 1987)
BUICK RIVIERA (1979 - 1985)
BUICK SKYLARK (1964 - 1979)
BUICK SPECIAL (1964 - 1969)
BUICK SPORTWAGON (1970 - 1972)
CHEVROLET CAMARO (1975 - 1992)
CHEVROLET CAPRICE (1977 - 1990)
CHEVROLET CHEVELLE 1973
CHEVROLET EL CAMINO (1970 - 1987)
CHEVROLET IMPALA (1977 - 1985)
CHEVROLET LAGUNA (1973 - 1975)
CHEVROLET LLV (1987 - 1988)
CHEVROLET MALIBU (1973 - 1983)
CHEVROLET MONTE CARLO (1970 - 1988)
CHEVROLET NOVA (1975 - 1979)
CHEVROLET S10 BLAZER (1983 - 1991)
CHEVROLET S10 PICKUP (1982 - 1991)
GMC CABALLERO (1978 - 1987)
GMC S15 JIMMY (1983 - 1991)
GMC S15 PICKUP (1982 - 1990)
GMC SONOMA 1991
GMC SPRINT (1971 - 1975)
OLDSMOBILE 442 (1964 - 1971)
OLDSMOBILE 98 (1978 - 1979)
OLDSMOBILE BRAVADA 1991
OLDSMOBILE CUTLASS (1964 - 1981)
OLDSMOBILE CUTLASS CRUISER (1980 - 1983)
OLDSMOBILE CUTLASS SALON (1975 - 1987)
OLDSMOBILE CUTLASS SUPREME (1967 - 1988)
OLDSMOBILE DELTA 88 (1977 - 1985)
OLDSMOBILE F85 (1964 - 1972)
OLDSMOBILE JETSTAR 88 (1964 - 1966)
OLDSMOBILE OMEGA (1975 - 1979)
OLDSMOBILE TORONADO (1979 - 1983)
PONTIAC BONNEVILLE (1977 - 1986)
PONTIAC CATALINA (1977 - 1981)
PONTIAC FIREBIRD (1967 - 1992)
PONTIAC GRAND AM (1973 - 1980)
PONTIAC GRAND LEMANS (1975 - 1981)
PONTIAC GRAND PRIX (1969 - 1987)
PONTIAC GRAND SAFARI (1977 - 1978)
PONTIAC GTO (1964 - 1973)
PONTIAC LEMANS (1964 - 1981)
PONTIAC PARISIENNE (1983 - 1986)
PONTIAC PHOENIX (1977 - 1979)
PONTIAC TEMPEST (1964 - 1970)
PONTIAC VENTURA (1975 - 1977)

Some models also used an ALUMINUM 9.5" brake drum as a further mass-reduction effort.

 

Wow, thanks a bunch, you are a wealth of information on the b-bodys. Ill order my brake parts for a 77 monte carlo becuase it has the 5x4.75 bolt pattern and hub pilot size as my 86 monte. Just have to find the right backing plates, i struck out on ebay.

 

Gm used to sell these backing plates new, part number 18002392, but since have been discontinued.

 

did you contact a dealer and ask that they do a system-wide check for any inventory of the part at individual dealers across the country?

What about aftermarket brake system suppliers, like Master Power Brake?

http://www.nastyz28.com/forum/archive/index.php/t-276185.html

The issue I recall with the "metric" Monte Carlo and other 78-88 G-body cars was the axle housing flange configuration (what the backing plate attaches to) was different compared to the 64-77 A body and 77-96 B-body, which were the same trapezoid pattern with 4 bolts to secure the backing plate.

Regarding housing flange configuration:
http://www.poltergeist.us/page/Elky/Brakes/rearend/original_axel.jpg
http://www.pro-touring.com/threads/103651-G-body-C5-C6-rear-disc-conversion-KORE3-kit
http://www.pro-touring.com/archive/index.php/t-29340.html


The G-body, with exception of the Buick GN (Turbo) all used a 7.5" rear axle, where the GN used the 8.5" axle. I'm not sure if the GN used the 4-bolt pattern backing plate, but I'm reasonably certain they still used 9.5" rear drum brakes.

 

did you contact a dealer and ask that they do a system-wide check for any inventory of the part at individual dealers across the country?

What about aftermarket brake system suppliers, like Master Power Brake?

http://www.nastyz28.com/forum/archive/index.php/t-276185.html

The issue I recall with the "metric" Monte Carlo and other 78-88 G-body cars was the axle housing flange configuration (what the backing plate attaches to) was different compared to the 64-77 A body and 77-96 B-body, which were the same trapezoid pattern with 4 bolts to secure the backing plate.

Regarding housing flange configuration:
http://www.poltergeist.us/page/Elky/Brakes/rearend/original_axel.jpg
http://www.pro-touring.com/threads/103651-G-body-C5-C6-rear-disc-conversion-KORE3-kit
http://www.pro-touring.com/archive/index.php/t-29340.html


The G-body, with exception of the Buick GN (Turbo) all used a 7.5" rear axle, where the GN used the 8.5" axle. I'm not sure if the GN used the 4-bolt pattern backing plate, but I'm reasonably certain they still used 9.5" rear drum brakes.

I never thought to do a system wide check for the parts, ill do that later today. Mp power brakes sells the complete 11" brake kit, it includes everything the backing plates, drums, and everything in between. But its 500 dollars, which is pretty high in my opinion. If i cant find the big backing plates, ill pick the smaller 9.5" drum brakes from a caprice and go that route before i spend 500 on the mp brakes kit.
You are correct, all of the gbody cars use the odd 3 bolt mounting flange on the.backing plate, and you are also correct, the g-body cars use a 9.5" drum.

So even if i use the smaller caprice drums, ill still be using the same size of brakes that the car was designed for. But yet, since im starting from scratch, i wanted to try and upgrade my brakes, if it doesnt work out that way, oh well.
Im not sure if i mentioned, im building a ford 8.8, but im having chevy ends welded on that will accept the large ford bearings, so instead of c-clips, my axles will be held on by a bearing retainer mounted behind a pressed on axle bearing.

 

I have a set of large drum backing plates and most/all of the brake hardware left over from a disc conversion. I'm not going to use them, pm me if interested.

 

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Vladimir, you gotta check the thread dates. This guy's was asking about backing plates in the year 2014.

-Brian

 

fixed.