'81 vs '82 Camaro backing plates...

Chebby · June 22, 2006, 10:57:49 PM

Hi all,

My project vehicle is a 1952 Chevy pickup.

I'm in the process of rebuilding a 1981 Camaro differential with 3:42 gears and posi for it. I tried to buy aftermarket 1981 backing plates but no one makes repops. 1982 backing plates are available but not the 1981's.

I'm extrapolating here but looking at lists, the brake drums are the same Raybestos part number for 9 1/2" x 2" from 1975 to 1992 Camaros. So if the drums are the same and I can fit the 1982 backing plates to my 1981 diffy*, I should be able to use the complete 1982 drum brake setup... Shouldn't I???

*Fitting the 1982 backing plates on the 1981 diffy might entail redrilling holes once I've mig'ed the old ones closed but I have a very well equiped shop.

I'm just wondering if anyone has done this swap before. Hey, if they can put early Buick finned drums on early Ford backing plates, then this should be a breeze!

Any comment would be greatly appreciated.

Chebby

enjenjo · June 22, 2006, 11:07:53 PM

The 82 Backing plates are very different than the 81 backing plate. The wheel cylinder actually mounts to the axle bracket through the backing plate. The 81 backing plates go clear back to 64.

Chebby · June 24, 2006, 07:57:18 PM

Hi Enjenjo,

I think I'm going to give this a try anyway. There has to be a way to convert '82 brakes to fit the '81 diffy ('81 diffy was free). RockAuto lists the same Raybestos part # for the Camaro brake drums and brake shoes from 1982 to 1992 inclusively. Dorman backing plates are listed as the same from 1978 to 1992. I'll keep you posted on my progress and what has to be adjusted or modified.

Keep in mind that I was the guy who waited 5 months for a Cen-Pen 3" dropped axle (had to change my handle to get back on the RRT) so I have LOTS of patience.

Chebby

Fat Cat · June 24, 2006, 09:34:46 PM

Quote from: "Chebby"Hi Enjenjo,

I think I'm going to give this a try anyway. There has to be a way to convert '82 brakes to fit the '81 diffy ('81 diffy was free). RockAuto lists the same Raybestos part # for the Camaro brake drums and brake shoes from 1982 to 1992 inclusively. Dorman backing plates are listed as the same from 1978 to 1992. I'll keep you posted on my progress and what has to be adjusted or modified.

Keep in mind that I was the guy who waited 5 months for a Cen-Pen 3" dropped axle (had to change my handle to get back on the RRT) so I have LOTS of patience.

Chebby

I am sure it could be done. However the end of the axle is different on the 82 up rears. They have a bigger end plate that the wheel cylinder retainer clip goes into to keep the wheel cylinder from turning in the backing plate. It doesn't work to good though. I had an Olds Cutlass that I had to replace the clip, wheel cylinder, and brake line about every 15,000 miles because of this design flaw.

If it were mine I would not do it. Have you checked with any of the aftermarket companies like Year One? This backing plate was used on alot of GM cars. Like Enjenjo said they were used for about 20 years. Even if you had to get a pair out of a year on the west coast to get a good set. I think it would be cheaper in the long run.

The reason that they make a replacement backing plate for the 82 up stuff is they are made from thinner metal and do not have any provisions to bolt the wheel cylinder into the backing plate. It uses a funky spring clip that wears out and allows the wheel cylinder to rotate in the backing plate. Once it does this it is time to throw out that backing plate and get a new one.

Also just because they use the same brake drum does not mean that everything is the same.

Chebby · June 24, 2006, 09:51:46 PM

Hi FatCat,

Thank you for your comments. Sounds like you're right, too many things to modify. Sounds like a dorky design, I guess I'll cancell those backing plates I have on order.

I didn't check with Year One but I did check with Classic Industries. Usually, when one supplier has a product they all carry it.

I'll do a bit of surfing tonight on the Year One site.

Thanks FatCat,

Chebby

tomslik · June 25, 2006, 08:59:54 AM

Quote from: "Chebby"Hi FatCat,

Thank you for your comments. Sounds like you're right, too many things to modify. Sounds like a dorky design, I guess I'll cancell those backing plates I have on order.

I didn't check with Year One but I did check with Classic Industries. Usually, when one supplier has a product they all carry it.

I'll do a bit of surfing tonight on the Year One site.

Thanks FatCat,

Chebby

what's wrong with yours?
i've got a 86ish here i'm not gonna use (all i wanted was the aluminum brake drums),....

Chebby · June 25, 2006, 02:05:10 PM

Those 1981 backing plates are nowhere to be found in the aftermarket.

"What's wrong with mine?" Well, the backing plates that were on the free differential housing that I got were worn right through where the shoes rubbed on the backing plate. I found another set that was much better on eBay but they're still not new. I'm going to have to build up those "rub areas" with the MIG and grind them flat. The anchor pin (brake shoe pivot) is also showing 1/16" deep signs of wear.

As Enjenjo says, the conversion to '82 backing plates and brakes is not feasible so I'm on the prowl again for a good set of '81 backing plates or fix the ones I got. Right now, I'm leaning towards fixing the ones I've got.

Thanks for the offer...

Chebby

Fat Cat · June 25, 2006, 02:28:34 PM

Quote from: "Chebby"Those 1981 backing plates are nowhere to be found in the aftermarket.

"What's wrong with mine?" Well, the backing plates that were on the free differential housing that I got were worn right through where the shoes rubbed on the backing plate. I found another set that was much better on eBay but they're still not new. I'm going to have to build up those "rub areas" with the MIG and grind them flat. The anchor pin (brake shoe pivot) is also showing 1/16" deep signs of wear.

Chebby

If that is all that is wrong with them I would fill in the wear marks on the rub plates. I would not worry about the anchor pin. I have done that many times.

Frank

tomslik · June 25, 2006, 05:35:45 PM

Quote from: "Fat Cat"
Quote from: "Chebby"Those 1981 backing plates are nowhere to be found in the aftermarket.

"What's wrong with mine?" Well, the backing plates that were on the free differential housing that I got were worn right through where the shoes rubbed on the backing plate. I found another set that was much better on eBay but they're still not new. I'm going to have to build up those "rub areas" with the MIG and grind them flat. The anchor pin (brake shoe pivot) is also showing 1/16" deep signs of wear.

Chebby

If that is all that is wrong with them I would fill in the wear marks on the rub plates. I would not worry about the anchor pin. I have done that many times.

Frank

me too, no point in wasting a bunch of time looking for 'em

enjenjo · June 25, 2006, 06:58:08 PM

If you want, you can use the 11" backing plates from a full size car the same era, and early 70's Grand Prix Pontiac drums for a big brake conversion. Or the 12" brakes from a Impala, but you will have to redrill the drums.