1970 k20 disc brake conversion

[kilokoa]

i need a little help here from someone that has done a disc brake conversion on a 1970 k20 with the aardvark open knuckle drum axle. I have a full dana 44 1973 axle here but the ring and pinion are toast. i was planning on doing the knuckle out swap and be done with it.

im getting mixed info from reading older posts on the forums. some say that it will not work because the axles are different lengths and width. and some say just swap the knuckle out and it its good to go.

so my question is can i use the 1970 axles and do the knuckle out swap or is it basically impossible because this year has one off parts that are not compatible with anything else?

[ohboy321]

Here is a page out of the Spicer parts catalog that lists the Bill of Materials/Part Numbers for the 70 and 73 D44 axles. Note that the part numbers for the axle assemblies are different between the 70 and 73.

The BOM is stamped into the axle. On my 70 K10 axle it is stamped on the drivers side facing forward.

I know that on the K10 D44, the axle shaft/u-joints were larger starting in 72.

Hope this helps.

[kilokoa]

Ok, thats verifies that the axles are different. I am wondering what i would need to make it work with the 73 wheel ends. New seals and bearings for the hub to fit the disc hub? I really dont want to tear into a perfectly working axle then find out its not possible.

[georgieb51]

Originally Posted by kilokoa

Ok, thats verifies that the axles are different. I am wondering what i would need to make it work with the 73 wheel ends. New seals and bearings for the hub to fit the disc hub? I really dont want to tear into a perfectly working axle then find out its not possible.

Did you ever find an answer to your question? I have a 1970 K10 that I would like to convert to disc brakes but I do not seem to find any conversion kits for it. I really do not know what I am doing, so I am wondering if someone could explain the problem with doing this on this truck. Thanks

[kilokoa]

I can't remember exactly what I did but I ended up buying rotors, calipers, pads, bearings, seals, pretty much much everything new from the knuckle out besides the spindles. All the parts I bought were for a 72k20. The axles were a different length and thickness so I used the older ones.

Besides having to buy a bunch of parts, it's pretty straight foward.

[kwmech]

Axle difference is the u-joint. Drum brakes utilized the spicer 260x joint and the later disc brake up to 91 in the Blazer and Suburban used the 289 joint (5-760x)

[57taskforce]

Also the shafts themselves on the 72+ are slightly bigger than the 71 down. But that won’t affect your swap. It should be pretty much straight forward, swap everything from the knuckle out with the disk break stuff. You could even use a donor axle for the parts.

[georgieb51]

Originally Posted by 57taskforce

Also the shafts themselves on the 72+ are slightly bigger than the 71 down. But that won’t affect your swap. It should be pretty much straight forward, swap everything from the knuckle out with the disk break stuff. You could even use a donor axle for the parts.

When you say the shafts are slightly bigger do you mean the diameter is larger? I am guessing that if they shafts were longer they would not work. I found a donor axle from 1991 Blazer. I am told that is the last year that will work for swapping

[1970cstblazer]

Originally Posted by kwmech

Axle difference is the u-joint. Drum brakes utilized the spicer 260x joint and the later disc brake up to 91 in the Blazer and Suburban used the 289 joint (5-760x)

All of 1971 and early 1972 disc brake Dana 44's used the smaller U-Joint, same as 1969-70 open knuckle drums. The bigger joint and updated seals were a late 1972 and up.

[57taskforce]

Originally Posted by georgieb51

When you say the shafts are slightly bigger do you mean the diameter is larger? I am guessing that if they shafts were longer they would not work. I found a donor axle from 1991 Blazer. I am told that is the last year that will work for swapping

Correct, I meant the larger axle u joints. Apparently that could be a late ‘72 thing per the post above but I’ve always understood it to be all the ‘72 model year trucks. My K20 had the larger joint 44 in it when I bought it (dana 60 now)
All of the 67-91 solid axles will interchange physically with each other as in you can bolt up a 91 axle into a 67. All of the disk brake dana 44 stuff will interchange between 71-80 which is approximately when GM started introducing the 10 bolt which is pretty much the corporate copy of the 44. Most parts between the 44 and 10 bolt will interchange.