Thank you gentlemen for responding. The battery I am using is a 4.8 volt nicad. At the time of the test it was freshly charged and the servo was plugged directly into the receiver. I also thought the gear backlash in the 8411 might be hurting me but the same condition happens with the 8231. Applying a small load does stop the oscillation but a small bump starts it going with increasing amplitude up to a point. I can try removing some of the balancing weight. Would it be better to have it balanced foward rather than aft?

Thanks,
Pete