2001 ford focus started vibrating last winter when I would back out of garage acted like brake was on hard to move. Since then I have replaces struts, brakes and drums, changed tran fluid, replaced tentioner pully, and now the vibrations is in all gears but still not all the time but more so when cold or has set a while. Could this be harmonic balance problem or motor mounts. (115,000 miles) serpantine belt changed at about 70 or 80,000

Check for stones caught in the engine mounts. Do you drive a lot on gravel roads? That is likely the problem.

Yes, my driveway is approx. 1700' of gravel!! Thanks I will have that checked

Check the engine mounts, I had same vibration, replaced 2 mounts and now on probs.