Replaced my driver's side axle / driveshaft with a new one after I started getting vibrations while accelerating. Solved the vibration problem, but a few hundred kilometers later my gear box seized up. Replaced the gear box with one from a junkyard, drove about 150 kilometers and the next day while driving around my parking lot the shaft just popped out of the gear box. Parts shop swears it's the right driveshaft. With everything fully assembled I can easily pull the shaft cup out of the gear. That doesn't seem right, but I'm wondering if someone with more experience with Ducato gears and axles might be able to comment. I've been told that it's normal for Ducato's not to have retainer clips on their axles, so I'm wondering if this behavior is normal, because usually a bit of effort is need to pull an axle out of a gear.
EDIT - The Gear side of the axle