LS Swap - E38/T42 powering LS2 and 4L80, no VSS no WOT shifting

[turabo87]

Hi fellow tuners, I've hit a road block with this one. LS swaps are not my typical tuning challenges so bare with me. It's a 1987 cutlass with an LS2 and 4L80, powered by an E38 PCM from apparently a 2010 Camaro SS and a T42. Trans harness was repinned for a 4L80. Main problem is I don't have VSS. Not sure if it's tune related or a bad VSS, but assuming it's the tune what can I try and look for? The vehicle shifts during light load (which I'm surprised it shifts at all without VSS). WOT is absolutely terrible, cuts throttle somehwere past 5k RPM and to shift I have to lift for a second then I can WOT again and it will shift 1-2, same technique to make it shift WOT 2-3, and won't shift at all to 4th.

Tune and logs attached. Any insight would be helpful. I've told the shop to at least diagnose the VSS to see if it's bad or not, but I suspect it's tune settings. They're not strangers to LS/LT swaps and they've said this combination has worked for them in the past with their previous tuner.

PS: Not sure if this matters, but when I first got the old tune read from the controllers, it was originally set as a manual gearbox. Old tune and new tune attached. I've also put accurate tire size information, final drive, and correct gear ratios for the 4L80.

[blindsquirrel]

There is no Camaro ECM OS that will communicate with a T42. You will need to change to a truck ECM/TCM OS combo.

A manual trans ECM, no matter what platform, will not send a VSS signal to an auto trans ECM. And a VSS wired to the TCM as it was originally will not send a VSS signal the manual trans ECM will be able to recognize.

You cannot change from a Camaro OS to truck OS using HP Tuners, the ECM will need to be done with SPS. Also will need to make sure you have an APP & throttle body compatible with the truck OS.

1GCPKPEA0AZ297318 is a valid 2010 Silverado E38/T42 VIN.

[blindsquirrel]

2009.5 Express van is another option, was available with 4L80 from the factory. That one would need a different ECM service number though, 2010-up is different and Express dropped the 80E in 2010.

1GBJG31KX91175952 is a late-'09 Express 3500, 6.0 & 4L80E.

The '10 Camaro (& '10 Silverado above) should be using 12633238, using an Express cal would need 12625455.

[turabo87]

Thanks for that quick response!! Could I perform a Write Entire to the PCM/TCM if I found and licensed a proper truck tune file?

[blindsquirrel]

Nope. Not with HPT. There are 8 segments in a Gen4 ECM, HPT only reads/writes 6 of them.

edit: I mean, you can. The software will not stop you from doing it. But you will have the two original segments left behind and they may not play nice with the new OS parts.

screenshot.06-02-2019 19.53.32 numbered.png

On the older Gen3 you can do it, as the throttle controls are in the external TAC module and not part of the PCM.

[turabo87]

So what are my real options here? Just get a truck PCM or do I need the PCM+TCM combo? The shop confirmed that the T42 TCM came from a 2008 Tahoe 4L60 2WD, but unfortunately the PCM says 2010 Camaro Manual.

[blindsquirrel]

Your existing 2010 Camaro OS that will never be able to talk to a T42 (not even a 2010 Camaro auto can talk to a T42, as all those used T43) can be SPS-flashed to turn it into a 2010 Silverado that can talk to a T42, as they use the same service number 12633238.

If you decide to use the Express van OS instead, that will require a different service number ECM.

I don't know how to tell you which one to use, because I don't know which pedal/TB you have since you didn't say, and I don't know if a pedal that works with the Camaro OS will also work with Silverado/Express.

All T42s are the same. There are about 300 different service numbers and they all interchange. The TCM can be write-entired in HPT to change OS/platform but if you have to get the ECM SPSed why not do both at the same time? Lots of independent shops these days have 3rd party scantools/passthru devices and SPS subscriptions and can reprogram modules in-house, it's not just a dealer-only thing or specialized tuner shops anymore.

[turabo87]

Your existing 2010 Camaro OS that will never be able to talk to a T42 (not even a 2010 Camaro auto can talk to a T42, as all those used T43) can be SPS-flashed to turn it into a 2010 Silverado that can talk to a T42, as they use the same service number 12633238.

If you decide to use the Express van OS instead, that will require a different service number ECM.

I don't know how to tell you which one to use, because I don't know which pedal/TB you have since you didn't say, and I don't know if a pedal that works with the Camaro OS will also work with Silverado/Express.

All T42s are the same. There are about 300 different service numbers and they all interchange. The TCM can be write-entired in HPT to change OS/platform but if you have to get the ECM SPSed why not do both at the same time? Lots of independent shops these days have 3rd party scantools/passthru devices and SPS subscriptions and can reprogram modules in-house, it's not just a dealer-only thing or specialized tuner shops anymore.

Pedal is from 07-13 Tahoe. Throttle is a DBW 92mm aftermarket unit from JEGS, I don't know brand.

[blindsquirrel]

Use the truck VIN/OS posted above.

Your existing TCM OS is from... '08 Express (24239927)? That's another incompatibility, there's a comms protocol change from early-'09 to late-'09 and they don't mix and match (late ECM can't talk to an early TCM). The 2009.5 Express 80E is using 24243356.

I think the late-'09 Express 80E T42 TCM OS will be able to talk to a '10 Silverado ECM OS without excessive weirdness.

[Frost]

What? You can run a T42 with a 2010-up LS3 Camaro engine base.. I can run a 4l80 or 4l60 with this combo. See attached pic.

[Frost]

I'm 99% sure that I converter a 2011 M6 to 4l80 and it worked with that ECM programming as well, about 5 years ago.

-edit-

Check out Alvin's 6l80 to 4l80 harness for 2010-up Camaro. He includes the TCM! https://www.pcmofnc.com/product/6l80...ion-harness-3/ With a little work, this can be used in a swap to run a late model 58x engine with Camaro ECM (and style TB and pedal) along with either a 60 or an 80. In fact MANY swaps mostly meet this criteria. I saw "many" because there are more truck ECMs floating around than camaros.

[Shrek]

I'm 99% sure that I converter a 2011 M6 to 4l80 and it worked with that ECM programming as well, about 5 years ago.

-edit-

Check out Alvin's 6l80 to 4l80 harness for 2010-up Camaro. He includes the TCM! https://www.pcmofnc.com/product/6l80...ion-harness-3/ With a little work, this can be used in a swap to run a late model 58x engine with Camaro ECM (and style TB and pedal) along with either a 60 or an 80. In fact MANY swaps mostly meet this criteria. I saw "many" because there are more truck ECMs floating around than camaros.

If the project you are recalling was actually in a Camaro - then, yes - it likely would have worked.

Camaros pickup vehicle speed from the wheel sensor, which is then broadcast over the CanBus network.

A decade ago I did a conversion tune for a customer with a twin-turbo 2011 Camaro L99 6L80 - which then received a full manual TH400. The speedometer continued to function normally.

If the project being discussed in this thread is a conversion / Hotrod (i.e. not a production Camaro) then the speedometer output may be an issue.

From the original post, the T42 TCM is running a 2008 OS, which will not communicate properly with a 2010 Camaro E38 OS. There will likely be a U0100 DTC being set by the TCM (or sometimes a P0700 DTC being set by the ECM).

[Frost]

Yeah you are right; it's been a minute. I forgot about the speed source. These were not swaps.