My 2001 Impala was getting a code 1811, it was shifting irregular and banging when put into reverse.
As per a previous post from another member the code was a PCS-pressure control solenoid problem.
My friend does transmissions, so he was able to repair with out pulling the trans out and replaced the PCS, another solenoid for the lock-up convertor and installed a fix type shift kit adjuster in the valve body.
My friend said this is a very common probelm for this transmission.
The car has not shifted this nice in over two years!
Thanks to the forum members who led me to this fix.
ronvb:grinyes:

Hi. Where are you from? Cause maybe i have the same problem(hard shifting, bang PtoDotR) I dont know what to think cause i dont have any SES light, i check alredy everything and still think my problem is missfire causing hard shift. And plus mechanics saying if no LIGHT then no problem(wich is stupid). Proabobly i have tranny problem. I am not mind to pay 100$ for diagnostic fee. By the way iam from NEW YORK (brooklyn) if you recomend me someone, i would be appreciated.

This problem does not throw a check engine light but it does set a trouble code without the light.You have to scan for trans codes.Cannot recommend
friend as he is retired and only works when he wants to.:grinyes:
ronvb