Purrs like a big cat



My '01 Ford Ranger (6 Cyl, 4WD) makes a purring sound when under load or going up a hill. The sound stops when the truck shifts into a higher gear. My mechanic suggested new spark plugs. Well, the sound is still there but it’s not as loud. I tried higher octane gas but this is not a “knocking” sound so that didn’t help.

What would?


Purring under load…an exhaust leak perhaps?


Have you checked the motor and transmission mounts?