Vehicle was not purring as usual, sounding more like a low rough growl. Alternator was changed, repair people said they thought was fine, twice. Now is skipping and they think it has a head-gasket leak. (Would that make it “growl” for a while first??) Am thinking more transmission…???
I respectfully suggest that you find new repair people.
A “rough low growl” can be the result of many conditions, ranging from something as simple as an exhaust problem to… God only knows. However, a transmission problem is not likely to produce a “low rough growl”.
Can you give us a more complete explanation of what that means?