Guitar Boogie & William-
Fluid change and filter seems to have corrected the shifting problem...other than the few metal particles and fluid showing a bit burnt, all checked out ok. The trans. is a 4L60E and have had absolutely no shifting problems (seems much smoother) after 300+ mi. From now on I'll be having it serviced at every 30K. Many thanks for the input.
Herb in Buna, deep East TX