There are two likely culprits that can cause your transmission to crunch when shifting gears.
If the transmission is reluctant to go into any gear, the most commonly found problem is in the hydraulic clutch system. This consists of a master cylinder (and reservoir), mounted to the brake booster and attached to your clutch pedal pivot pin, and a slave cylinder is mounted to the bell housing of the transmission. These two cylinders are connected via rigid metal line and a flexible rubber hose. Since the slave cylinder operates out in the elements, subjected to road dirt, water and salt, it's the more likely problem. The good news is that slave cylinders are relatively inexpensive. We recommend replacing the flexible rubber hose, if it's more than a few years old, since it can become degraded internally and cause problems--and it's also inexpensive. You should also consider replacing or rebuilding the clutch master cylinder; it's a bit easier to do now, since you have to bleed the system anyway.
Another common failure is the clutch pivot pin. The weld beaks internally on Alfas and prevents the pedal from operating the master cylinder.
If your Alfa transmission goes into gear relatively easily when you put it into gear in your driveway, but makes a crunching noise when you shift (especially into 2nd gear), the problem is likely to be worn synchromesh rings. There’s nothing special about second gear, except that it tends to get the biggest workout--especially around town. Unfortunately, synchromesh is quite a bit more expensive to fix than a clutch slave cylinder. To make the repair, the transmission should be rebuilt with new synchros (plus seals and any other worn bearings and gears). As an alternative, IAP has rebuilt Alfa transmissions, so you can swap yours out without waiting for a rebuild.
Transmission Shifting Replacement parts