Make a timing record
From normal operation, note whether the noise starts before air reaches the rooms, with strong airflow, or after heating stops. Record whether it changes pitch or becomes a rattle. Include whether the furnace completes heating, stops early, or shows an accessible fault code.
The main blower's job is to move heated air into the home. Trane describes that air path in its blower explanation. Trane main-blower function.
That relationship makes airflow timing useful, but it is not a parts test. Sound can travel through the cabinet and connected materials, and more than one component can operate at the same time. A nearby transformer, loose panel, or other source may sound motor-like.
Ask the technician to show the basis
Have the technician compare the sound with the actual sequence and inspect the implicated component. Ask what evidence shows a mechanical, electrical, mounting, or airflow problem and whether any safety concern remains. If replacement is recommended, ask which part, why it fits the diagnosis, and how the result will be checked.
Do not remove access panels, hold down the door switch, change speed taps, or lubricate a motor from a generic video. Some motor designs do not call for owner lubrication. The exact equipment's service instructions govern.
A new, harsh sound or changed heating behavior calls for service sooner than a stable, familiar operating sound. Stop use through the normal owner control if a severe new noise occurs and there is no suspected gas leak. Do not keep running it for a better recording.
Your next step is to send the timing record and existing safe recording with the furnace model to the technician. Use the distinction to guide diagnosis, not to order a motor before the finding is confirmed.