RunawayRadio

iTrader: (2)

Hi guys,

I've been searching for this one for a bit and haven't come up with a definitive answer on an LC9 swap in my car. I have my eye on a 5.3 out of a 2013 silverado and am debating on how to approach the wiring with a digital dash. The actual engine wiring is identical between an analog and digital car, but there are some additional sensors and wiring like the dash temp, coolant level and a couple others i'm forgetting off the top of my head. Is there much of a difference between making up a standalone harness for the swap vs integrating the digital dash harness to the new motor wiring directly? The intent is to match the two as close as possible for a factory like and factory appearance install.

Some context (current config of car):

• 87 Firebird GTA w/digital dash and TPI 350
• 1994 Firebird T56
• Repinned 700r4 connector for VSS and reverse lockout signal
• Repinned ECM connectors for EBL Flash
• Upshift indicator pin added to dash cluster, harness and ECM
• dakota digital SGI-5e

Intent:

• Retain all 87 Factory dash functions
• Retain T56 lockout
• Remove and fuse all connected fusible links in 2013 distribution block/fusebox (starter ring connections for example)
• Retain factory fuseblock where appropriate
• Retain C100 connector (dismantle connector/sealant and rebuild for use with new harness)
• Reuse and repin existing dash connectors where appropriate
• Retain OBD 2 connector in factory third gen location

Thanks!

johnw999

I swapped an LC9 into my 1984 Trans AM. First thing I did was delete the VVT and DoD with kits from Texas Speed and Performance. I also got a cam from them based on my expectations. Texas Speed was easy to work with. The LC9 has a 58x reluctor. I used a harness from Speartech. I had them program my ECM too. Speartech is expensive for what they offer. And that’s all I have to say about that.
I added a cable connection to my T56 for the speedometer from http://t56cablespeedometer.com . Your speedometer is electronic, so you’ll have to research that. The coolant, voltage, and oil pressure inputs can be identified on the C100 plug. My installer tapped an oil pressure port on my LC9. Thirdgen has a write up on that. Good luck

Pocket

iTrader: (24)

Absolutely
A stand alone literally runs the engine/trans and nothing else. Several optional things are usually included (gauges, fans etc) but you must connect them yourself. These are great for an old classic that doesnt have any existing wiring to repurpose, but a semi-modern chassis like 3rd gen has all you need already. Id suggest reading the LS1 swap sticky at the top of the forum and thumbing through the wiring threads. There are a few extra steps for a GEN IV 58x engine over a traditional LS1, but not many. Those are mostly the requirement for DBW and some extra programming to get tach/speedo going

Your upshift light will be inop completely. I can go into why if you want, but the short of it is it cant work with the GEN IV ECM alone
You'll have to add pins on the E38 ECM and update the tune to change the outputs to something an analog gauge can handle. Reason being is no ECM 08+ outputs an analog signal, they're all high speed LAN, class 2 serial or CANBUS. Modern clusters are basically computers with stepper motors twisting dials for outputs instead of screens. Classic clusters like yours are basically a box with a bunch of analog components. This is why 4th gen dash swaps use a LT1 cluster if not accompanied by a LS swap. Those are still analog. GEN III LS guys got lucky as two unrelated systems required analog tach/speedo inputs so they could be directly repurposed in a swap. GEN IV do not, so similar unrelated systems using a type of speedo/tach are selected and the output frequency is changed to something similar to an analog with a big conversion factor. Companies are catching up to this by offering modules that plug into a ALDL and output analog signals, but its really not necessary in this case

To make things easier, you may want to build it like a GEN IV LS2/3 harness with a TR6060. The diagrams will better match up to what you're after and the ECM tune will be closer to your end result

lsx-bmc

Highly recommend this video from lsxmatt. He goes over each gauge and posts links to different things you'll need to look into in the description

RunawayRadio

iTrader: (2)

That's totally fine. I wouldn't expect modern communication standards to be even remotely compatible with 30 year old, steam powered tech .

If the option still exists to output a correct signal to an analog gauge with a conversion factor, great. If it's not really feasible, I'm no stranger to adding interface modules as needed to translate a signal. As for the upshift indicator, if there realistically a way to keep the function in the gen IV ECM? as long as there is compatible if/then logic in the controller, i would hope one of the output pins could be re-purposed as an on/off binary switch. I spent some time digging around online for this first and didn't find a definitive answer. Then again, i'm not a tuner and am probably asking the wrong questions.

Awesome. There's a couple things in that video I hadn't thought about yet. Thanks!

RunawayRadio

iTrader: (2)

Bump. Would anyone know why the digi dash upshift lamp cannot be re-purposed in an E38 ECU? It's an obscure enough question i'm not able to find it on google or search.