upshift, downshift!

[S10xGN]

Hi All,

Last few times I hammered my truck (shifter in "D"), it made the 1 - 2 upshift, then immediately downshifted. Of course, I let off not knowing what the deal was. What might cause this? I haven't been able to drive it lately due to heavy rains in our area...

 

[chris718]

a sticking 1/2 shift valve train assembly or a croosleak interconnecting hydraulic circuits.