Conversions & Hybrids - LQ9 auto to manual & general q's

I'm kind of overwhelmed with the search feature.. so here goes...

I've got an lq9 with wiring harness and pcm from a 2005 escalade. I want to make this setup work with a T56. I'm sure many people have done this, if someone can guide me to those threads, I'd really appreciate it. I have a spare 98 manual harness that I can cut up to salvage the trans plugs.

Another thing I'm having a hard time finding info for is, what is the part # for the tac module and pedal assembly. My PCM has the service #: 12589463 and hdw #: 12589162. I need to know this information so I can pull off the right stuff when I'm at the junkyard. I don't want to convert to dbc since this pcm doesnt have the iac module in it.

Turns out a little more complex than I expected, and I'm on my second truck/manual trans swap.
I've got an 05 L59 (flex fuel 5.3) on a muncie in a 72 Olds 442. Same ecu as yours.
It's using the 12573059 tac, black plastic with metal mounting tabs. I've got a used one if you need it.
For the pedal, get a non-adjustable for an 03-05 GM truck, not the adjustable Escalade. Check the dealer, they're only about $100.
The VSS input should be programmed for the manual trans reluctor.
Disable all the auto trans stuff.
If you want to have cruise control, you'll need to add CPP and brake switches.
There's another issue with the tune. On my ecu that had an auto trans, the rpms tend to over rev when the gas pedal is dropped and the clutch engaged. On an ecu that came from manual trans truck, the rpm drops as soon as the clutch is engaged. Still working to figure that one out.

Turns out a little more complex than I expected, and I'm on my second truck/manual trans swap.
I've got an 05 L59 (flex fuel 5.3) on a muncie in a 72 Olds 442. Same ecu as yours.
It's using the 12573059 tac, black plastic with metal mounting tabs. I've got a used one if you need it.
For the pedal, get a non-adjustable for an 03-05 GM truck, not the adjustable Escalade. Check the dealer, they're only about $100.
The VSS input should be programmed for the manual trans reluctor.
Disable all the auto trans stuff.
If you want to have cruise control, you'll need to add CPP and brake switches.
There's another issue with the tune. On my ecu that had an auto trans, the rpms tend to over rev when the gas pedal is dropped and the clutch engaged. On an ecu that came from manual trans truck, the rpm drops as soon as the clutch is engaged. Still working to figure that one out.

i think im going to just get rid of the 98 pcm & harness, 05 escalade lq9 auto pcm & harness and trade it all for a 2000 manual harness and pcm if anyone is interested.

Turns out a little more complex than I expected, and I'm on my second truck/manual trans swap.
I've got an 05 L59 (flex fuel 5.3) on a muncie in a 72 Olds 442. Same ecu as yours.
It's using the 12573059 tac, black plastic with metal mounting tabs. I've got a used one if you need it.
For the pedal, get a non-adjustable for an 03-05 GM truck, not the adjustable Escalade. Check the dealer, they're only about $100.
The VSS input should be programmed for the manual trans reluctor.
Disable all the auto trans stuff.
If you want to have cruise control, you'll need to add CPP and brake switches.
There's another issue with the tune. On my ecu that had an auto trans, the rpms tend to over rev when the gas pedal is dropped and the clutch engaged. On an ecu that came from manual trans truck, the rpm drops as soon as the clutch is engaged. Still working to figure that one out.


why should i be using a non-adjustable pedal?

The adjustable is a massive assembly that will fit nicely in a Mack truck.

i think im going to just get rid of the 98 pcm & harness, 05 escalade lq9 auto pcm & harness and trade it all for a 2000 manual harness and pcm if anyone is interested.

Running two extra wires is too much work?

Leave the auto trans connector unplugged ziptied out of the way somewhere. VSS doesnt change. ISS for 4L80E harnesses gets left alone, unplugged. Find the reverse lock pin on the PCM and add one wire strait to the connector, then the other wire to 12v IGN

Thats it

Running two extra wires is too much work?

Leave the auto trans connector unplugged ziptied out of the way somewhere. VSS doesnt change. ISS for 4L80E harnesses gets left alone, unplugged. Find the reverse lock pin on the PCM and add one wire strait to the connector, then the other wire to 12v IGN

Thats it

<3 thank you! i'm going to steal the reverse lock out switch and reverse light switch connectors off my 98 harness and just use the 2005 dbw harness

Good choice, it would be more work to add IAC and the seperate IAT/MAF than to splice a couple wires for the trans.
Just be sure your tuner knows how to set up for a manual trans.
<3 thank you! i'm going to steal the reverse lock out switch and reverse light switch connectors off my 98 harness and just use the 2005 dbw harness

Id order a new set of trans connectors and sell the 98 T56 harness. Uncut Fbody harnesses fetch a nice little bit

Where do you get the T56 transmission connectors?

Where do you get the T56 transmission connectors?

If interested I have all 3 pigtail connectors brand new with about 8 inches of wire, I bought them for a project and never used them, How's $20.00 shipped for all 3? Its the vss, cags, and reverse plugs

That sounds great to me. pm me with payment details

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