03 Impala Intermittent Hard Shifting with 1811 code

[blksuperman409]

yes i just got mine changed... i have a 03 impala...

[03imp]

My 03 had a diagnostic test and came up with code p1811. Felt slight slip when driving and excellerating. Not major just annoying, was like pressing the gas and letting up and pushing again. Does not happen very often .Mechanic recomended transmission flush. Suggested that this would fix the problem. Is that possible?