redrilling 6 lug axles to 5 lug - brake drum interchange????

[Chuck78]

I'm having my 62 GMC's original Dana 44 rear axles redrilled to the 5 lug pattern to go with my future 5 lug disc brake swap and a set of American Racing Torque Thrust D wheels that I got a super deal on.
The axles are no problem, Babbit Bearings here in town charges $100/pair for the axles. The center registers on the axles need turned down from the 3.5" diameter to the newer wheels' 3-1/16" (I think?) center register diameter. Now I hadn;t thought of this, but if I have the 6 lug drums redrilled and use them, now I won't have the center register to locate the drums anymore! I thought I could maybe have them turn it down in a step type register, but I figured it'd be far easier if I could just find a modern 11x2" drum that would swap right onto the Dana 44 rear.

Anyone have any clue what could work?

this is what is stock, and it is listed both for Chevy and GMC (Dana 44 and GM Corporate rear ends):
RAYBESTOS Part # 2005R More Info {Professional Grade; Outside Diameter 12.375" / 6 Bolts / Not Finned}
Front; 11" X 2" Brakes
Rear; 11" X 2" Brakes

All of the newer style starting at the very beginning of the 1/2 ton 5 lug pattern have what looks like a stepped drum that is thicker towards the end, as they are still 11x2 brakes, but larger diameter on the edge at 13.64" vs the 12.375".
Not sure if the newer drums will work with the old backing plates, and if they are going to be the right depth.
The D44 is far superior to any GM Corporate rear, but no axle conversions are available, but I still want to stick with this unit if I can. Not sure if the entire backing plate would swap out with a GM rear, but maybe I could get a D44 backing plate and brake setup off of a Jeep or something if the pattern is the same? Mine bolt on with the axle bearing retainer, but I thought I had read someone having a D44 with backing plates that were factory welded on.

Photos:

[markeb01]

I did exactly what you are suggesting on my 1960 GMC/Dana 44 about 10 years ago. I don't remember the part numbers, but the brake drums I used are the finned version shown on the right.

I do remember I had to measure several brake drums at different part stores to get a pair that matched the depth of my shoes, from the backing plate to the mounting surface on the axle flange. The first pair I bought from a discount outfit were not deep enough, and the rear of the brake shoes hung out the back of the drum. Just make sure to check, because all of them were for the same application but they did not all have the same depth dimension. The stepped portion of the drum is to accomodate the fins. The inner brake drum looks like the non-finned version. The inner flange fits inside the backing plate, then steps over the backing plate lip and extends away to the rear of the fins. This both improves cooling and helps keep crap from entering the brake assembly better than the original.

As best I could determine, the early GMC/Dana 44 backing plates are unique to the early GMC application in the area where the emergency brake cable enters the plate. The only style e-brake cables available are the conventional type with spring fingers for retention. My 1960 GMC had an odd bracket arrangement that held the end of the e-brake cable in place with a bolted bracket.

I tried to find replacement backing plates with the conventional e-brake hole, but came up empty. I searched every wrecking yard in the area, and went thru probably 200+ vehicles from Mopars, Jeeps and Dana 44 Blazers, etc and could not find any backing plates that would fit the axle flange on my rear axle, other than the stock 1960 GMC style. Ultimately I had my son fabricate welded adapters that bolt to the backing plate like the originals, but accept the normal spring finger attachment. Being a 1962, yours may or may not have the same problem.

One tip on redrilling the axle flange - as best I remember one of the 6 lug holes ends up overlapping with the 5x5 pattern. Rather than puddle welding the hole, the machinist sliced down a regular wheel stud, keeping only the spline portion. That was pressed into the hole and tacked in place. This eliminated the need to puddle weld the hole, running the risk of overheating and warping the axle flange.

I also agree regarding the D44, it's a great axle. Mine was originally a 3.70 which I had swapped to a 3.08 about 15 years ago, and then to a 4.09 about 5 years ago when I converted to a 4 speed manual. I would not want to swap it out for anything else.

Good luck, M.

[Chuck78]

so you're saying that the stepped part just sticks out over the Dana 44 backing plate, vs the originals that just come flush to them?

That';s strange that different manufacturers drums would vary that much. I suppose our D44 shoes must ride further inboard than the newer brakes are supposed to, so it must just be riding on the very edge.

[markeb01]

Originally Posted by Chuck78

so you're saying that the stepped part just sticks out over the Dana 44 backing plate, vs the originals that just come flush to them?

Yes that's how they fit on mine. the brake drum portion fits just like the original and the fins surround and extend beyond the backing plate. I'd pull a wheel and take a picture, but there's really not much to show, it just looks like a factory installation with the drum in place.

I was surprised at the variances also. Some were up to a 1/4" too shallow. It could be the GMC/Dana44 backing plates are odd, but the original drums are the same as the same year Chevy. The mismatched drums I got may have been manufacturing defects, or packaged in the wrong boxes for a different application, etc. The internal depth should match the same dimension on your original drum and then you know they'll fit.

[Chuck78]

I got my axles back today! I ended up going to AutoZone and getting a set of Duralast # 8819 finned drums for the 11"x2" 1984 C10 application. No tape measure, but I measured by marking a pencil at the depth and it looks like it will work (I hope!).

Looked up various applications. Seems that 67+ vans used the 5 on 5 11X2 brake drum in the Raysbestos version at least, up to an 89 Suburban for the same drum! Found some available for some models that weren't on others, yet the Raysbestos was listed for pretty much any finned 11x2 application.

71 C10/87-89 Suburban lookup:
RAYBESTOS Part # 2065R
RAYBESTOS Part # 2065
ACDELCO Part # 18B16

84 C10/88 Suburban lookup:
RAYBESTOS Part # 2065R
RAYBESTOS Part # 2065
ACDELCO Part # 18B16
WAGNER Part # BD60294
Duralast Part # 8819

Funny how the 2065 and others work on all applications, but then the Wagner and a few others seem to just work for the 88 suburban, even though the 88 suburban 2065 also fits 87 and 89? This might have something to do with what markeb01 was finding with the difference in depths. Or maybe it's just bad parts interchange information! Seen that also!

[Chuck78]

that's the inside face view of the Wagner finned drum. looking at my duralast, I see that it is basically like my originals but with fins added and an extra step out that extends beyond the backing plate, as you can see in this photo.

[CircusWagonJim]

I have a '58 GMC Dana 44 and switching to new axles with small center register. If I wanted to use new axles with the smaller center register would the jeep or Suburban drums go right on? Is there a drum that will work that comes with 4-3/4 GM passenger car pattern? Thanks Jim