Changed engine, now tranny will not shift.

OK, I've got a 2003 Grand Prix SE that HAD a 3100 V6. The block was cracked so I found a 3400 V6 out of a 2002 Impala. Everything bolted up perfectly...even the EGR valve.

As I wrapped it up and took it for a test drive I noticed the TEMP gauge wasn't working, the speedometer wasn't working and the transmission wouldn't shift out of first gear...WTF!?:crying:.

I'm sure I'll have to change engine harness and coolant temp sensor for the temp gauge. But would that have any affect on the transmission? I was thinking maybe the pins are in different locations on the harness plug....Looks like the Impala had dummy lights as far as the temp gauge goes...

Any help, opinions, and observations would be GREATLY appreciated.

Nevermind!!! I fixed it....I had pinched the yellow wire from the VSS...Poor car just didn't know it was moving and didn't want to shift the transmission...Now just gotta change the harness to fix my temp gauge and I'll have successfully completed the 3100 to 3400 V6 swap....Yay ME!!!

Congrats on rechecking your work and finding the problem....

Curious if you swapped PCM with the engine? Reason I ask is the 3100 PCM is not going to have fueling tables (injector pulsewidths) for that larger displacement. There is some range that it will self-correct to try to maintain O2 sensor signal toggling.

HOWEVER...when you break into power enrichment trying to use that extra displacement you are back to open loop where the injector pulsewidth doesn't get modified (will alter spark to keep from knock).