Vibration during around 30 mph during acceleration
I think a mechanic will check the driveshaft. Anyone else have a better guess?
Maybe engine mounts. At 13 years of age that wouldn’t be unheard of.
Bent wheel or axle would do that, too
If it’s purely speed related and the vibration comes through the seat or your feet, I’d start looking at the transmission mounts and work my way back through the u-joints and the rear axles and wheels. If the vibes come through the steering wheel the whole front suspension is suspect, start with the wheels.