A bent axle, and a donor coded 3S73

The inspection that has been gating the whole rear of this truck since teardown came back worse than a differential question. The axle housing is bent - a straightedge laid along the tube shows daylight - and the internals are assumed to have gone with it. The original cast lift block came off with a hairline fracture running above its second locating boss. That is not a differential repair any more. It is an axle.

Finding a replacement was the one part that went quickly. The search across salvage inventory was run with Claude, which read through listings far faster than doing it by hand and cut a long list down to two low-mileage candidates within driving distance: a unit in Kentucky out of a flood car, and one in North Carolina from a front-end wreck. Flood damage and a differential are a bad pairing - water sits in the housing and nothing about the outside tells you what the bearings did - so the North Carolina axle won on the simple ground that a front impact says nothing about the rear of a truck.

It is a 2024 PowerBoost donor with roughly 30,000 miles, bought for $2,200 with the rear lower cab cap thrown in. It brings a compatibility question with it, and this is the part worth writing down because no search turns it up. This truck's door label codes the axle L6 - a 3.73 ratio with the electronic locking differential. Its axle tag reads 3E73. The donor axle is tagged 3S73. The internals look to be the same on the 9.75-inch ring gear, so the risk is not mechanical: it is whether the locker's sensor harness plugs into what this truck has. The yard will supply a pigtail to splice if it does not.

What has not been confirmed is whether the donor's own door label also reads L6. That is the cleanest way to settle the ratio and locker question before anything is unbolted, and it is one photograph from the yard. The PowerBoost is a hybrid, so identical ratio and locker still would not rule out different sensor provisions.

The axle gets collected in person in North Carolina shortly. None of this is settled until it goes in, and it has not gone in. Both outcomes get written up here - a failure would be worth more to another owner than a success.