2007 Pontiac G6 GTP - 3.6L - Transmission Changed To 2008 Help

Thanks to everyone in advance,

I have just swapped my transmission on my '07 Pontiac G6 GTP (3.6L, A6) to an '08 and I am having issues:
1. Speedo is not working.
2. Manual mode is not working (which I'm not really worried about).

Here are the OLD SETTINGS:
TCM OS: 24240291 C714
ECM OS: 12611134 172A

Here are the NEW SETTINGS:
TCM OS is: 24244551 E46C
ECM OS: (SAME)

When I first tried to write settings from the old setup, I got an error saying that the operating systems didn't match. I then hand copy-and-pasted all the settings from the old transmission into the new and re-flashed the vehicle. Speedo still does not work; it moves, but it will read about 18mph at 50mph. I have no MIL at this time.

Does anyone have any ideas?

So the TCM wasn't flashed with the same OS/VIN as the computer?


People run into this issue on the RWD 4L60e/6L80e if they got a used transmission. The TCM should be flashed with a dealer level tool, then it normally all jives together again.

Thanks for the reply.

The ECM is the same, the VIN is the same, the TCM is different - but the NEW TCM was programmed with the OLD TCM settings. I was crossing my fingers to not get a dealer involved in this.......