Someone said it's probably the vibrator and they're probably right, that's usually the thing that goes out. However, look closely at your speaker and look for rips and check if it's generally just all dried out and brittle.
According to the radio fact sheet that I have here, the vibrator is a Motorola part number 48B3333 which crosses over the Cornell-Dubilier #5342 and Radiart #5342.
The speaker is Motorola part #50C511815, alternate part #50K511815, field resistance is 4.3 ohms.
I hope that helps.