LS3 /4L70 GMCC tranny issues

[stinger67]

We're working out the bugs & tried to take my 67 out on its first test run yesterday.
It's a LS3 / 4L70 GMCC.
The 4L70 would not shift out of 1st. No problem going from neutral, reverse & park. When we go anywhere from Drive - down, it just stays in 1st. Anyone ever run into this?
We called around to some of the guys who have done swaps, most of them talked about making sure the pin connections were good, making sure the wires were all in the right pins.
All double checked now, still nothing.
Any ideas?

[dontlifttoshift]

I'm pretty sure that you have the wrong vss cable hooked up to the transmission. There is one that comes from the engine harness and there is one that comes from the transmission harness. You need to use the one from the engine harness.

From the engine control kit instructions.


Vehicle Speed Input - optional
The ECM is programmed and looking for 40 pulses per revolution
typical for automatic transmissions. The LS Control System harness
is designed to plug into the output speed sensor of 4L60 & 4L80
Transmissions, which have a 40 pulse output. NOTE: If you are using
the CP Supermatic Connect and Cruise Transmission Control
System, the vehicle speed input must be plugged in.

[stinger67]

I'm pretty sure that you have the wrong vss cable hooked up to the transmission. There is one that comes from the engine harness and there is one that comes from the transmission harness. You need to use the one from the engine harness.

From the engine control kit instructions.

Donny, thanks, but we already went that route, no luck.

[dhutton]

Did you tap into that VSS signal for a speedo or something else?

Don

[dontlifttoshift]

Do you have the bulkhead connector between the ecm and tcm connected?