2010 Camaro 6L80 Swap
 

I doing a 6L80 swap from a 2010 Camaro into a 70 Chevelle. Where do get a speed signal for a Dakota Digital speedometer?

You are not alone with this problem. I am going to use a Speedhut speedometer that uses the signal from the GMLAN communication wires. Maybe Dakota Digital now does the same thing. Some are experimenting with pin J1-57 on the E38 ECM. That may or may not work. The signal may have to activated in the software using something like HP Tuners.

Pin 57 can normally be turned "on" with the right tuning software. The Camaro does not use this pin from the factory.

So the TCM sends the signal to the ECM over GMLAN? Does the TCM need that turned on in their software?

The TCM broadcasts the speed over the CAN/GMLAN by default. Normally a matter of turning pin 57 on in the ECM, though plenty of variations from GM of course :).

HPTUNERS -> Speedometer -> General -> Speed output type -> vehserial