Re: 2003 Ford Expedition front end intermittent groaning / vibration
Front axles are the worst to work on, even for a shop.
I'd definitely take it back as they didn't resolve the issue. A lot of people assume that when in 2wd mode, the front axle doesn't turn, when in fact it's just not under power through the transfer case and all the front end parts do in fact turn with the wheels.
I wouldn't rule out a bad wheel bearing that may have contributed to the noise. Getting the gears reinstalled is no easy task. You have to get the preload just right as if they aren't meshing properly, it'll cause you more grief quicker than you know.
As for my Dodge, I have a 9.25" axle in the back and whatever axle in the front, but it's given me no problems at either end in the hard 140K miles I've had it. It's towed, thrown off road when I had the lift and larger tires on (33") and I've done nothing outside of regular magnet cleanings and gear oil change every 2-3 years. It's a tank. The frame has 7 crossmembers (compared to the Dakota with the longer wheelbase that has 5). Less chassis flex helps durability and I do a one, two, or even a three wheel peel no less than once a week (full time 4wd). When a major part goes, I'll hold a proper service before replacing it.
'00 Durango R/T 360ci 290hp (modded); 138,500m
'06 Pontiac G6 GT 3.5L 220hp; 44,000m
'12 Chrysler 200 Limited 3.6L 283hp; 13,000m
'99 Taurus 3.0L 2V Vulcan 145hp; 154,300m - Traded
Amsoil in all vehicles!