To have the stock rear axles...
To have the stock rear axles and brake drums redrilled to match the new bolt pattern of the front disc brakes, I took my Stepside to Brian Elbert at B&D Fabrications. Brian does this kind of work, along with other rearend repair and modification, everyday, but the process still takes about 5 hours to complete.
If you are going to the trouble of upgrading the brakes on your C10, you are more than likely going to want to have matching wheels on the front and rear of the truck. Since the upgrade to the front from stock drum brakes to disc brakes in the accompanying article changed the bolt pattern from six lugs to five lugs (5-on-5 bolt circle), it's necessary to address the rear axles in order to have matching wheels. You have a couple of options in how to go about doing this. To keep your existing rear axle housing, you can change the bolt pattern by replacing the axles (and brake drums) with new ones in the bolt pattern you need or you can have the axles and brake drums redrilled. If you choose to have the axles redrilled, you should install new wheel studs, rather than reusing the old wheel studs.
In either case, you will be required to remove the axles from the housing. To do this with a typical GM truck rearend, jack up the truck and secure it safely on jack stands if you are not using a garage lift. Put the transmission in neutral, as you will need to be able to rotate the gears in the differential. Place a drain pan under the rearend cover and then loosen the cover bolts enough so that the gear lube drains out of the rearend. While the gear lube is draining, remove both rear wheels. When the gear lube has drained out of the differential, completely remove the bolts securing the cover and set the rearend cover aside (letting it soak in a parts cleaner would be a great idea). Now remove the cross-shaft retaining bolt and then pull the cross-shaft outward. The cross-shaft does not need to be removed completely, just enough so that the axles can be pushed inward. When the axles are pushed inward, the axleshaft C-clips should fall right out. The axles can now be pulled out. After pulling the axles out of the housing, inspect them for wear or other damage.
While the truck was up on...
While the truck was up on the lift, it was a good time to take a closer look at the underside of my relatively new project. The trailing arms look to be in satisfactory condition. While the brake line is bent and routed vey sloppily, it does work. Most likely it will be replaced eventually, especially if the stock rear drum brakes are upgraded to discs. The lower shock mount "adapter" bracket really should be eliminated. Setting the truck to the desired ride height and then replacing the shocks with those of the appropriate length would have been a better fix than installing this mounting plate.
The first step is to remove...
The first step is to remove the rear cover and drain the gear oil to gain access to the cross-shaft retaining bolt and cross-shaft.
Before the axles can be removed,...
Before the axles can be removed, the wheels and tires must be removed. Then the brake drums will need to be removed so the axle can be pushed inward.
The cross-shaft retaining...
The cross-shaft retaining bolt must be removed and then the cross-shaft (round bar stock parallel to the ring gear) is pulled outward enough so that the axles can be pushed inward. When the axles are pushed inward, the C-clips that retain the axles within the housing will fall out, allowing the axles to be removed.
If you choose to replace the axles, you will first need to determine the axle diameter, axle length, and number of splines, and then find suitable replacements that have the desired bolt pattern. Unless you are able to purchase new axles that meet your specifications, you will need to verify that any candidates for replacements are not bent or otherwise damaged in any way that would make them unusable or short-lived.
If you have access to a machine shop that routinely redrills axles and brake drums, this is perhaps your best bet, as you already know that the axles are the correct size and will work. For our '68 C10 project, we chose to forego the salvage yards looking for axles, and went straight to B&D Fabrications to have the axles redrilled. The intent was to have the brake drums redrilled as well, but there were already several holes in the existing brake drums, so those were replaced with new drums. After Brian Elbert at B&D Fabrications does his magic on the axles, they can be reinstalled.
The axles can be pulled out...
The axles can be pulled out with relative ease. Just avoid pulling them out partially and applying any force that may cause them to bend. After pulling the axles from the housing, check them for wear or damage, and repair or replace as necessary.
Brian uses a small grinder...
Brian uses a small grinder to remove the remnants of any previous gasket material from the rearend. All traces of the old gaskets must be removed for the new gasket to seal properly. With the gasket removed and the gear lube drained from the differential, Brian uses aerosol carburetor cleaner to aid in removing any gunk that may be within the housing. This also helps to clean the ring gear to check for signs of wear.
The stock axle is chucked...
The stock axle is chucked up into a metal lathe with the inner end of the axle centered in the headstock and the flange end centered in the tailstock. The steady rest is then positioned in the same location where the axlehousing bearings are.
While the large-diameter wheels...
While the large-diameter wheels that were on the truck had no interference problems, the new rally wheels would not fit over the brake register. The wheels were on hand, so they could be measured and the brake register sized accordingly. An extra step that Brian performs is to size the brake register to the correct size for the brake drums so that they are centered correctly. This is not a big difference, and may not even be necessary in some people's minds, but it is a little task that should help to reduce any rotational vibration that could present itself if not done.
After locating and drilling...
After locating and drilling the holes to 0.500 inch, they are reamed to 0.515 inch diameter.
When changing the bolt pattern...
When changing the bolt pattern from any five-bolt pattern to another five-bolt pattern, the holes could simply be offset equal distance from each other. However, changing from a six-bolt to a five-bolt pattern makes it a little more complicated. The discoloration around the bottom hole in the photo indicates where one of the existing holes was welded shut and then a new hole drilled in the same area. The walls of the original holes are slightly brown (rusty), while the newly drilled holes appear as fresh steel.