I recently had my transmission flushed and filled to see if it would solve this problem. It helped two years ago when my tranny was slipping so I went and had it done again but no luck. It shifts great again but when I select 1st or 2nd, there is nothing there when I hit the gas. Any ideas what may be causing this? Drive and overdrive work fine with smooth shift but nothing in the other two selections. Any ideas would be helpful.