10" drum brake swap for BP change

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wlecat

wlecat

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I have a 1967 Barracuda with a 1969 (A Body) 8-3/4” (489 diff case) .
I picked up some axles from Dr. Diff with 5X4.5 BP (nice!)
Purchased some new (73’?) 10” drums with 5X4.5 BP holes, deep (2.5 depth),
along with a brake hardware kit and 10”x2.5” shoes from Classic Ind.
The drum fits to the existing back plate, but the shoes won’t come together at the top.
Do I need a different back plate? Adapter? What?
I don’t think I can still use the old 1.75” shoes and I don’t really want to.
Has anyone run into this?
 
Are the shoes and everything attached to the backing plates? Can you post a picture to see what the problem is?
 
You need backing plates, shoes and brake drums to all match. The conversion axles are generally done to accept the 2 1/2 wide shoes so if that is your case you need the correct backing plates.
 
Figured as much, I'm thinkin' the backing plates are not readily available at Autozone or advance...maybe NAPA.
Anyone know what year or P/N I should ask for? maybe '73?
Is there a previous thread I might have missed that could tell me?
 
did the 10 x 2 and the 10 x 2.5 use the same backing plate? if so you would think a guy could use 2.5" shoes and hardware then get a 10 x 2.5 drum with the bbp (as you already have) and bolt everything up using the axles set up for the b-body offset. it all boils down to the offset of the baking plates.
 
dartnfish said:
did the 10 x 2 and the 10 x 2.5 use the same backing plate? if so you would think a guy could use 2.5" shoes and hardware then get a 10 x 2.5 drum with the bbp (as you already have) and bolt everything up using the axles set up for the b-body offset. it all boils down to the offset of the baking plates.
Click to expand...

No, the 10x2 and 10x2.5" do not use the same backing plate.

All BBP axles use the same axle flange offset (and that offset is different than SBP axles). That means the wheel mounting surface is in the same place for all of them, regardless of the brake width. Which means that the backing plates must be matched to the drums. If you have 10x2.5" drums, you need 10x2.5" backing plates. If you have 11x2.5" drums, you need 11x2.5" backing plates. Same for 11x2" drums, 11x3" drums, etc.

By doing it that way you can use the same axles for all of the different BBP brake combinations. If the backing plates were all the same, the axles would have to be different for each of the different brake drum widths.
 
Get Salvage yard 2.5" brake plates and parking hardware from an 8 3/4" , 60-70's, Satellite, Fury, Van, Dart, Valiant, and buy new drums, springs/hardware, steel gasket between backing and flanges, foam under bearing retainer; all from Autozone. Their new drums are balanced without the weights and have low run-out. Paint the plates with canned Epoxy, and the drums with brake paint.
 
aracer01 said:
Get Salvage yard 2.5" brake plates and parking hardware from an 8 3/4" , 60-70's, Satellite, Fury, Van, Dart, Valiant
Click to expand...

Good luck finding one of those in any of the typical local yards. I know it does happen, as I've pulled from cars like that, but it is not the norm.

Fortunately, 10x2.5" BBP brakes and backing plates were run on cars all the way up into the late 80's. Some of them will need to have the "5th hole" drilled as they'll only have 4 holes to mount the plate, but that's it.

CHRYSLER CORDOBA (1975 - 1983)
CHRYSLER IMPERIAL 1981
CHRYSLER LEBARON (1977 - 1981)
CHRYSLER NEW YORKER 1979
CHRYSLER NEWPORT (1979 - 1980)
CHRYSLER TOWN & COUNTRY (1977 - 1981)
DODGE A100 (1964 - 1970)
DODGE A108 VAN (1967 - 1970)
DODGE ASPEN (1976 - 1980)
DODGE B100 (1971 - 1980)
DODGE B150 (1981 - 1989)
DODGE B200 (1971 - 1980)
DODGE B250 (1981 - 1989)
DODGE CHALLENGER (1970 - 1974)
DODGE CHARGER (1966 - 1974)
DODGE CORONET (1965 - 1974)
DODGE D100 PICKUP (1970 - 1987)
DODGE D150 PICKUP (1977 - 1987)
DODGE DART (1973 - 1976)
DODGE DIPLOMAT (1977 - 1989)
DODGE MIRADA (1980 - 1983)
DODGE RAMCHARGER (1978 - 1983)
PLYMOUTH BARRACUDA (1970 - 1974)
PLYMOUTH BELVEDERE (1965 - 1970)
PLYMOUTH BELVEDERE II (1965 - 1967)
PLYMOUTH CUDA (1970 - 1974)
PLYMOUTH DUSTER (1973 - 1976)
PLYMOUTH GTX (1967 - 1971)
PLYMOUTH PB100 (1975 - 1980)
PLYMOUTH PB100 VAN 1974
PLYMOUTH PB150 (1981 - 1983)
PLYMOUTH PB200 (1975 - 1980)
PLYMOUTH PB200 VAN 1974
PLYMOUTH PB250 1981
PLYMOUTH ROADRUNNER (1968 - 1975)
PLYMOUTH SATELLITE (1965 - 1974)
PLYMOUTH SCAMP (1973 - 1976)
PLYMOUTH TRAILDUSTER (1978 - 1981)
PLYMOUTH VALIANT (1973 - 1976)
PLYMOUTH VOLARE (1976 - 1980)
 
Thanks guys. Glad that information is out on the forum now too. Big help.
 
To summarize and simplify what's been said here: Stock A body axles use stock a body backing plates & drums. The axles have a different offset (distance from the backing plate to the end of the hub) and the backing plates have to match that.

B/C/E/F/J body and trucks use the more common axle offset and backing plates/drums.

When you convert to large bolt pattern on an A body housing with aftermarket axles or "cut down" B/C/E body axles, it effectively becomes a B/C/E/F/J body rear. The axle offset is the more common one. You then have to use the more common backing plate which comes on EVERYTHING. It's not hard to find them. LBP 7.25 rears 8.25 rears. all 8 3/4s except a body, trucks, F bodys, J bodies with 10 inch brakes.

If you REDRILL your a body axles to LBP they are still A body axles with the A body offest, then you have to stay with the original A body backing plates and you have to redrill your drums to LBP also. THAT'S a bigger PITA.

Just remember that the drums and backing plates must match the axle offset.
 
from cuda/chally forum..........." question, would a big drum setup that was on a junkyard 8 1/4 or 9 1/4 bolt onto my 8 3/4?
Yes the backing plate is the same for 7 1/4 - 9 3/4 diffs so it will bolt up the only issue would be drums from an A body with the smaller 4" bolt pattern or the 80 & newer Dodge trucks with 5" bolt pattern"
 
Got a pair of 8-3/4 A body back plates from Dr. Diff - they fit perfect, the drums fit up nice and my yellow beast fish made it's first cruze nite appearance last week
 

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