'99-02 SRW Superduties got D50's, the duallys got D60's.
'03 and up is all D60.
If the axle is from an '01 its either a D50 or its a dually front end. The dually front end makes it not worth much.
The biggest downfall to a '99 or newer superduty axle is that it uses a metric lug pattern which means you have basically no choice in wheels. You can use stock Ford wheels or buy SUPER expensive aftermarket wheels and even then you only have a few to choose from.
Its pretty common to see Superduty 60's go for a few hundred bucks because, well, they're not that good.
I'm not trying to argue with anyone, but alot of misleading info is being posted. ALL F350's SRW/DRW had 60 fronts, in '03 Ford stopped making the Dana 50 in their F250's and Excursions. Essentially, a Dana 50 is a 60. The only difference is the ring and pinion, and neck down inner shafts. The ring gear is just a fraction bigger than a Dana 44. ALL other parts are the exact same in the Super Duty years, i.e., knuckles, hubs, outer shafts, etc. The housing looks exactly the same, until you pull the diff cover off.
The wheels are metric, 8x170 bolt pattern, '05 and up are also factory coil sprung and use a different offset than previous years. Wheels are not any more expensive than your standard 8x6.5 bolt pattern, if you don't want different bolt patterns F/R look into the Sterling 10.5 rear end from the same truck. (comparable to a GM 14 Bolt in strength) Also, these axles are called super 60's, they have 35 spline inner and outer shafts from the factory.
The weaknesses are the ball joints and unit bearings, but it is like everything else, mechanical. It's going to break eventually. If left neglected long enough kingpins will get loose and wear out too, causing some serious death wobble and drivetrain issues.
Biggest mistake Ford ever made was getting rid of the 7.3, the engine was tried and true, I have seen many of them with over 300,000 miles on the clock and stick chugging along.
