LS3 swap, electrical help

WP29P4A said:

A place in So. Cal did the conversion. If they were real humans I would not be cleaning up their mess, and no they are no help, or I would not be here asking you guys. Very thankful for your input. I got the speedometer worked out and I'm just about ready to test it.

The part/model # on the ECM is LS3761480.

The gauge manufacture says connect straight from VSS signal to speedometer.

Click to expand...

That is the chevrolet performance connect and cruise kit for the 376/480hp LS3. It uses an E67 ECU.

https://www.jegs.com/p/Chevrolet-Pe...6-480-Engine-Controller-Kit/2480268/10002/-1#

The VSS to speedometer will only be accurate if you have some way to calibrate the speedometer for vss pulse/mile which will be different based on axle ratio and tire size. 30 minutes with HP tuners would have been enough to fix the speedometer and tach with the old cluster, as long as it was reading something. You will likely need to spend the same time to get it right even with the new cluster.

What is running the transmission? Is it a 6 speed?

Bextreme04 said:

Oh no. The gauge conversion will not fix them being inaccurate. You need to get into the tune and correct it there. EFILive or HP tuners would let you get into the tune and adjust the parameters to read correctly with whatever gauge you are using. It is unlikely that these new gauges will just suddenly read accurately without more adjustments in the tune. The RPM is coming off the crank/cam signal and is interpreted in the ECM, adjusted according to the parameters in the tune, and then output as whatever signal you spec in the tune.

The speedometer signal is similar, but comes from the VSS on the transfer case and is then adjusted by factors in the tune to get the correct reading at the speedometer.

Click to expand...

Yes I believe it is a 6 speed trans. The instructions with the speedometer show how to calibrate regardless of tire size, etc. Not a problem. I found the port in the Jeep and the ECM to USB cable, in case I need to do programing, like you mentioned. Just about ready to test the speedometer and gas gauge.

I really appreciate the tips and suggestions, thank you.

They tried all kinds of adapters/converters to fix the tach and speedo issues, none worked.

If this other company didn't get this straight, it really makes me wonder what else is screwed up on it. Where is the VSS? What transfer case and trans is it using? Some of the automatics have a real hard time with low ratio and engine braking if they use the wrong VSS signal. If this is a 6L80, the VSS is internal to the trans and you HAVE to get the speedometer signal off the ECU unless they put a VSS on the transfer case.

Bextreme04 said:

If this other company didn't get this straight, it really makes me wonder what else is screwed up on it. Where is the VSS? What transfer case and trans is it using? Some of the automatics have a real hard time with low ratio and engine braking if they use the wrong VSS signal. If this is a 6L80, the VSS is internal to the trans and you HAVE to get the speedometer signal off the ECU unless they put a VSS on the transfer case.

Click to expand...

I have been correcting everything they didn't finish for the last year. You are correct, and yes they did install a VSS on the transfer case where the drive shaft connects.

Just an FYI, I'm not fighting you on your programing suggestions, I agree and figure I will end up there, eventually. I have to get the wiring done and working before I worry about programing. I am logging your suggestions into memory so when I get there, I will have an idea what to do. The owner and I keep talking about how to get access to the ECU.

Since you mentioned programing, what program do I need to download?

WP29P4A said:

I have been correcting everything they didn't finish for the last year. You are correct, and yes they did install a VSS on the transfer case where the drive shaft connects.

Just an FYI, I'm not fighting you on your programing suggestions, I agree and figure I will end up there, eventually. I have to get the wiring done and working before I worry about programing. I am logging your suggestions into memory so when I get there, I will have an idea what to do. The owner and I keep talking about how to get access to the ECU.

Since you mentioned programing, what program do I need to download?

Click to expand...

That late of an ECU will require HP Tuners or EFI live unfortunately. You can try your hand at Universal Patcher, but you likely wont be able to do anything transmission related with that. If you are planning on doing more work with EFI in the future, HP tuners is probably worth having anyways. It will run you $400-500 to start and then $150-ish per extra vehicle you want to tune.

If this is running a 6L80, the TCM is inside the transmission. If it's a 4L60, 4L80, or 8L90, you will have a separate TCM mounted somewhere as well.

LOL, none of this is planned and I hope I don't have to do much more of this. I'm an audio/video, low voltage installer. This is just some hobby bs I do for good friends or really good clients when their mechanics do low quality work. People usually don't hire me to do the install, they hire me to fix what others have done. I don't advertise and my phone number is unlisted, I hide from this kind of work. If they hunt me down and ask properly, and pay well, I suck at saying no. It feels good when it's done and I get to look like a rock star when my wiring looks great and it actually works.
Hanging TV's and installing surround sound is much less stressful, and it pays better.

I got the speedometer and gas gauge connected and tested, just have the tach to do tomorrow. I think the client has a friend that builds cars also and has some kind of programmer, so I'm hoping I don't have to do it. Thanks again for the help and info, definitely helped lower my stress level today.

WP29P4A said:

LOL, none of this is planned and I hope I don't have to do much more of this. I'm an audio/video, low voltage installer. This is just some hobby bs I do for good friends or really good clients when their mechanics do low quality work. People usually don't hire me to do the install, they hire me to fix what others have done. I don't advertise and my phone number is unlisted, I hide from this kind of work. If they hunt me down and ask properly, and pay well, I suck at saying no. It feels good when it's done and I get to look like a rock star when my wiring looks great and it actually works.
Hanging TV's and installing surround sound is much less stressful, and it pays better.

I got the speedometer and gas gauge connected and tested, just have the tach to do tomorrow. I think the client has a friend that builds cars also and has some kind of programmer, so I'm hoping I don't have to do it. Thanks again for the help and info, definitely helped lower my stress level today.

Click to expand...

Glad it is working out! I hate fixing other peoples screw ups, but have been known to get sucked into helping out other peoples projects too. If the tach reading is still off by some multiple, and it doesn't have a way to adjust it on the gauge, there will be a setting in the ECU that can be adjusted to get the right pulse output.

I'm going to cheat today, I'm going to pull the cover off the ECU and put my toner on the tach wire and find it in the dash. It's really pissing me off that I cut the tach wire that was running to the original cluster and now I can't find it in the dash.

WP29P4A said:

I'm going to cheat today, I'm going to pull the cover off the ECU and put my toner on the tach wire and find it in the dash. It's really pissing me off that I cut the tach wire that was running to the original cluster and now I can't find it in the dash.

Click to expand...

Yeah, the only thing left to do on my swap is redo the factory harness that I'm going to use. I'm not looking forward to it, and have been putting it off for a while. I'm planning on ringing the wiring out, removing everything I don't need anymore, and then generating new wiring diagrams for what I've done to it so that I can troubleshoot and repair in the future if I need to.

I printed a copy of the manual this morning and pulled the ECU first thing. Found the tach wire pretty quick after getting access to the ECU connectors. Got it all back together and working, still need to calibrate the gas gauge and speedo. Going to have to hard wire the dome lights since they were controlled by the original gauge cluster which is also the "Body Controller module" for the jeep.

You have to be a contortionist and be able to do tie wraps one handed, to work on jeeps. The interior reminds me of an over sized high chair in an under sized out house, with a basket ball pressed against your chest.

Bextreme04 said:

If this other company didn't get this straight, it really makes me wonder what else is screwed up on it. Where is the VSS? What transfer case and trans is it using? Some of the automatics have a real hard time with low ratio and engine braking if they use the wrong VSS signal. If this is a 6L80, the VSS is internal to the trans and you HAVE to get the speedometer signal off the ECU unless they put a VSS on the transfer case.

Click to expand...

The short story is, client brought the jeep down to So. Cal for the conversion. It was supposed to take 4 to 6 weeks to do. Client was done messing around at the 6 month mark and got it back, unfinished and untested. Thankfully the client is very skilled at building cars, off road race vehicles, classics and just about anything motorized, does his own fabrication, so he was able to finish setting everything else. He just doesn't like doing advanced electrical wiring.

@Bextreme04
Well, it took 12.5 days to complete the wiring, but it all works. I drove it for the first time today to calibrate the Speedometer and test the tachometer. It was nice being able to use the app on my phone to compare what the gauges were reading. The transmission has a speed sensor inside and there is a speed sensor on the end of the transfer case.
One of the hardest things to rewire was the dome lights, that were controlled by the (body module) gauge cluster. Getting them to work off the door switches and a switch on the Switch Pro unit took some time and thought. Having to mix a tach signal with voltage and resistors, to make the tach respond seemed like a poor design. Actually making the new gauges and LS-3 conversion work together without a wiring diagram was a challenge. I had ECU pin configuration and colors of the wires connected to the terminals, but not where they come out of the loom and what color they are at the other end.

The Switch Pro 9100 was a top shelf product, and the instructions and install were straight forward. It looks and works great, I would highly recommend it for controlling accessories. It can be controlled and programed from an app also.

Bextreme04 said:

Glad it is working out! I hate fixing other peoples screw ups, but have been known to get sucked into helping out other peoples projects too. If the tach reading is still off by some multiple, and it doesn't have a way to adjust it on the gauge, there will be a setting in the ECU that can be adjusted to get the right pulse output.

Click to expand...

The new tach does have internal settings for the pulse rate, I set it to 2 and it matches what the Chevy computer displays on my phone app now. The only part of fixing someone else's screw up, that is enjoyable, is asking the client how much they paid the guy that messed it up. "If you paid that guy $100.00 per hour to screw it up, what am I worth?"