Faulty Replacement Mount?

[doratheexplorer]

1995 Voy, 3L, 3-speed tranny, 114K miles.

Symptom: After replacing front motor mount, vibration in the dash/steering off throttle: slowing with or without braking, full stop, and always in gear. Vibration is only noticeable to the driver, does not occur in park or reverse, and only after warm up cycle.

Discussion: I'm thinking I should continue to replace the left and right mounts, even though these appear without cracks, no clunks revving or turning, etc. Is this symptom typical of single, front mount replacement, or might the new mount be faulty?