Here's the dilemma: For most forms of off-roading, you can't beat a short wheelbase. That's why Jeeps, early Broncos, Scouts, and the like are so popular. In the fullsize spectrum, that's also why Blazers, Jimmys, Ramchargers, and 1/2-ton trucks are the rage. But with any of the fullsizes, you get a 1/2-ton running gear with tons (literally) to stress the axleshafts, gears, pinions, and driveshafts. These components have their own way of letting you know when you've asked too much.
It's no surprise that the most popular upgrade you can make to these vehicles is to swap in 3/4- or 1-ton axle assemblies. This fixes almost all the shortcomings of the lighter-duty axles, and in most cases the parts aren't that difficult to install.
The truck used for this conversion is a '76 GMC 1500 that came with a Dana 44 frontend and a 12-bolt rearend. Dana 44s were used until mid '77, when the 10-bolt frontend became 1/2-ton equipment, and 10-bolts replaced 12-bolts completely in '83. Both 3/4- and 1-ton GM trucks used 14-bolt rears, so the real difference is in the front. Through mid '77, the 3/4-ton frontend was the same Dana 44 used under 1/2-tons. The rotor and hub were different and had the eight-lug wheel pattern. The 1-ton trucks used a Dana 60 up front, which is the ultimate in strength, but these are extremely pricey pieces. If your tire size or type of wheeling demands the strongest you can find, you'll want the 60.
The 14-bolt advantage is undeniable strength while the drawbacks include cost, lost ground clearance under the pumpkin, and weight. In addition to larger pieces and a pinion that's fully supported, eight-lug 14-bolts are full-floaters. This means that the weight of the vehicle is on the hub instead of the axleshaft.
Weve heard both ends of the spectrum regarding swapping a 1/2-ton to 3/4-ton gear: Its more expensive and difficult than you think versus its an easy bolt-in. We went to Off Road Unlimited to find the truth and realized that, while its not a 100 percent bolt-in procedure, its not that intimidating either.
The crew at Off-Road Unlimited (ORU) does plenty of 3/4- and 1-ton axle upgrades in addition to all sorts of custom and bolt-on work on four-wheel drives. After discussing a few options, a 14-bolt was selected for the rear of this truck while the original Dana 44 frontend would be converted to eight-lug. The first step is to strip the front axle of all of its steering, brakes, and axle components. | 
The spindles used on 1971 through mid-1976 model Dana 44s were a little smaller in diameter than those used on late 1976s through 1987. Maurice Rozo at ORU says that the larger spindles bolt onto the earlier housing and are a little stronger. The larger ones from either a Dana 44 or 10-bolt will fit an earlier 44, and they will require later hubs to match the larger size. | 
An ARB Air Locker and 4.56 gears were going into the pumpkin of this Dana 44, so the axleshafts were removed too. The stubshafts, axleshafts, knuckles, and steering U-joints are all reused for a 3/4-ton conversion, so inspect them for wear and consider changing the steering U-joints since you have them out of the axlehousing. |
Other maintenance you should consider while the frontend is torn apart is whether to replace the ball joints. These take a beating if you 'wheel hard, and they usually aren't considered until they separate. The added expense of changing them is minimal with the axle taken apart. | 
Eric Garding at ORU set up the ARB Air Locker and Precision 4.56 gears in the 44. The copper air line from the collar required that the driver-side main cap be modified for clearance. The line then snaked around to the top of the housing where a bulkhead-type fitting was installed. | 
Garding used an inch-pound torque wrench to measure the drag on the pinion. He also used the marking compound included in the full installation kit from Reider Racing to check pinion depth and gear contact. |
With the locker installed and the gears set-up, the axleshafts can be installed. The only parts really changed to make the Dana 44 a 3/4-ton are the brake rotor and hub. You can either buy these new as a unit, which comes with the studs pressed in, or find a used pair, which is much more economical. The original 1/2-ton brake backing plate and caliper are retained. | 
A GM Corporate 14-bolt is found under 3/4- and 1-ton two- and four-wheel-drive trucks, making them fairly common. They were also used under dualies and vans, but these have different overall widths from regular pickups and Blazers, and the spring perches are in different locations. If you're doing a swap on a 1973-1987 truck, Blazer, or Suburban and are looking at one that's not bolted in a truck, the rearend you want is 72 inches from end to end (measuring from the end of the axle-retaining bolts), 66-1/2 inches from wheel flange to wheel flange (with drum brakes), and the leaf-spring centering-pin holes are 42-3/4 inches apart. For 1967-1972 trucks, Blazers, and Suburbans, you'll need one 70-3/4 inches wide, 66-3/4 inches from flange to flange, and 40 inches from pin to pin. | 
A 14-bolt is a heavyweight in more than one way; it tips the scales at about 525 pounds fully dressed with drum brakes. That does wonders for axle droop but makes it a serious pain to install. Gary Valencia positioned the rearend on jackstands (using an engine hoist) to lower the truck onto the rear. |