Gears For Rears
Rebuilding the Dana 80 Rear End on Project Box Hauler
There’s no debate that diesel-powered pickups are the absolute best when it comes to hauling heavy loads. With lots of low-end torque and turbocharged horsepower, diesels are the truck of choice for serious haulers. Such is the case with Project Box Hauler.
A former Castrol Racing show car hauler, which racked up more than 200,000-plus miles while repeatedly pulling a fifth-wheel trailer across the country, the ’01 Ford F-350 was showing signs of serious wear and tear when the owner got his hands on it last year. Since that time, we’ve addressed nearly all of the motor issues with new injectors, an upgraded fuel system and exhaust, and also tossed in a new Centerforce clutch in the six-speed.
The rear end on this dually is the last weak link in the driveline we had yet to address. When we did the initial assessment, things didn’t look too good inside the massive Dana 80 rear end. There were metal shavings all over the magnetic drain plug and the rear-end fluid looked less than ideal when drained. The biggest concern was the massive amounts of side-to-side play in the ring gear carrier assembly, which you could literally move by hand. Years of towing a heavy fifth-wheel apparently took its toll on the Dana 80 to the point where the only option left was to either replace the entire differential or crack it open to see if it was rebuildable.
Since the owner is on a budget with this truck, we opted for the latter. We rolled the big dually to the gear experts at 4Wheel Parts in Mesa, Arizona, where store manager Glenn Gruettke did the autopsy. Turns out, the housing was still straight, but the carrier bearings were wasted, which caused most of the side-to-side slop. Glenn also recommended we replace the entire carrier and basically rebuild the whole rear end since the spider gears in the carrier were also well worn.
The folks at 4Wheel Parts were the logical choice for doing the rear-end rebuilding. Besides having more than 50 stores nationwide, these folks do gears for a living, and know the intricate ins, outs and shortcuts that make it easy to set up a rear end the right way. For the rest of us, setting up a differential is one of those exact sciences better left to the experts since you’re dealing with shims, backlash, preload and other stuff that the average driveway mechanic shouldn’t be messing with.
The rebuild recipe for the dually was simple: Keep the same gear ratio and replace all the internals with the same stuff as stock—Dana/Spicer parts and bearings. This included a new open carrier assembly, complete with all-new spider gears and shafts, bearings, seals and new 3.73:1 gears. Since the truck is a dually, and doesn’t do any sled pulling or boat-ramp duty, the owner opted to replace the open diff with another one, although this would have been the time for any gear changes or the installation of a Posi-traction carrier or traction device.
The following photos highlight the install of the new parts. Cracking open a differential is easy; putting it back together correctly is where the science comes in. Since the Dana 80 is massive, the bulk of the labor is in getting the carrier in and out several times until the right shims are in place, and making sure that the backlash is correct. With new gears in place, there is a break-in period associated with them, according to the folks at 4Wheel Parts. The gears need to go through several heat cycles without towing before the fluid is changed again and the rig is ready to haul, usually after 500-plus miles.
If your diesel is a high-miler and you’re hearing strange noises coming from the differential, it might be time for a rear-end rebuild. Even though this may represent a serious investment, especially if you opt for a gear change or the addition of a traction control device, your truck’s rear end is where the power meets the pavement, and is the last vital link between making forward progress or sitting on the side of the road.