01 Transmission into an 03 Impala??

I bought a good used transmision from an 01 Impala and want to put it into my 03------but have now been told by several people that it will not work.

Can anyone tell me what the differences are, and if there is a way to modify the 01 Tranny so it will work in my car. (both cars are 3.4's)

Any and all advice will be appreciated

Will fit and look inside the big round plug for a color(not the wiring harness plug) and this is real easy to do.The color of the plugs have to match and the gear ratios have match too,will not work right with the wrong gear ratio.Al you have to do is change the final drive.

Hey WA, Thanks for the advice and great information. I got some add'l info about my 2 trannies, and wonder if this add'l info will allow you to add anything to your advisory.

I looked at the 2 transmissions and here is what I have:
ON MY 03:
has a Gray plug, with brown in the middle
White Tag says 613RDBW0C9X
Tag also has some stamped numbers in the upper right that are 224, 2A, and 03

ON THE 01 I picked up:
has a gray plug with green in the middle
White Tag says 611RDBW125J
Tag also has some stamped numbers in the upper right that are 209, 2A, and 00

Does this help clarify if I can make the swap, and what I have to do to make 01 fit in my 03?

You might have a problem going from a 01 to 03 the PCS is different and are not interchangeable do to different spring rates in the valve body and your computer will not have the right programming to make it work with the 03 style PCS You more than likely can do a complete VB and separator plate swap if you do that just make sure you get a new PCS for the 01 model year. The early PCS have a wear issue and fail quite often.