Another 8l90 stuck in Neutral-T87A Problems

[jaketillmann86]

I've seen a few threads from others having this problem with swaps and such, so I thought I would add my experience in a new thread.

I put a 2018 Silverado l83/8l90 in my Jeep Jk using an rpm extreme kit. I have tried many different TCM's with this setup:

Stock T87A unlocked by HP tuners- stuck in neutral, would not go into range
T87a from 2017 Escalade- shifted through all gears fairly well but was a bit rough in some gears, so I took it to the dealer to have the stock 2018 OS and solenoid data loaded into it, after that was done the jeep wouldn't shift into range, I suspect they changed something about the OS in mid 2018 that doesn't jive well with the swap kit, which uses a can computer without utilizing the L83 BCM
T87 from 2016 Tahoe- will not shift past 3rd
t87 from the same vehicle that the 2018 L83 powertrain came from, just 2016 instead- will not shift past 3rd

Is there anyone around Fort Wayne, Indiana that can load just the 2018 solenoid data from my 2018 into one of my 2016 TCM's? Any input on whether you think this will allow the 2016 T87 to shift through all gears?

Can anyone confirm that I would be able to load the solenoid data myself if I pick up a mongoose or MDI and subscribe to TIS? My concern is that I will get off board programming error messages since I am not using a GM BCM.

TIA

[IARLLC]

TIS won't let you program a T87 behind a E92A (2017up) PCM. If you want to run a 2015.5 or 2016 T87 you need to find one from a vehicle that had the exact same combination and deal with the just deal with the affects of wrong solenoid data. Or if you have access to a 2015.5 or 2016 8 speed vehicle with the correct gears etc, you can plug your T87 into it and run it through the whole TIS process inputting your transmission's solenoid data at the right time. I have done that. It works. That will give you good results in the long run. Not that handy but the benefits of running a T87 are handy (no extra license fee, unlocked, readable, etc, etc).

[jaketillmann86]

Thanks for weighing in, your past posts have been a big help as I try to sort this out.

For some reason the OS from a 2017 vehicle seems to work well with the swap.

Any idea if a dealer is able to load the 2017 os to my stock 2018 T87A, but retain the stock 2018 solenoid calibration?

[IARLLC]

With SPS you don't get to chose the OS that goes in. It depends on the VIN. There are cases where I have been able to input a different VIN in BCM, Radio, Cluster for custom installations but these TCMs are usually programmed together with the PCM in combination so they depend on the VIN of the PCM. Solenoid data is just printed on the tag on the trans so you do get to input the solenoid data yourself during the process.

Hope that helps.

[vannatta20]

The issue is Rpm extreme programming of their can bus module. 2018 and up transmissions go to limp mode because of the module. I went thru this on our own development. The only fix is for rpm to figure out the fix or change your transmission to a earlier model.

[IARLLC]

As long as you have an 8L90E a T87 is an option but since the T87 was never offered with the 10 speed they are stuck with the T87A.

[vannatta20]

You can not use a t87 on a 18 and newer 8l90. The internal prndl is different and the tcm will not work. A t87a must be used on 18 and up. In 2019 the changed part numbers on the t87a and it needs to be used on 19 and up 8 speeds. It?s getting complicated!

[IARLLC]

16 T87 to 17 T87A was a big change. A lot of people tried to run the T87 in their 17s but gave up when it was not set up right and did not work out. Truck forums are full of stories of people stating that can't be done. But T87 works pretty well in place of a 17 T87A if you have the way to set it up as I have.

I did not realize that these were more such changes going up to 18. I have not tried that.

[jaketillmann86]

But this doesn?t explain why my stock 18 T87A puts the tranny into limp mode while the multiple 17 T87A goes into range just fine.

I took one of those 17 T87A to the dealer to try to program in the 18 OS and solenoid data using the stock 18 ECM, then it also sent the transmission into limp mode. I did this thinking something about the hptuner unlock service messed things up, but I ruled that out.

So I bought another 17 T87A and the matching ecm. I tried to use the 17 ecm to program new 2017 OS into the original unlocked 18 T87A, but the dealer was getting error messages. I suspect the 18 T87A OS is what is not playing nicely with the swap. Could VATs be the reason we were unable to program via the stock 17 ECM?

[tunerpro]

Could VATs be the reason we were unable to program via the stock 17 ECM?

VATS is not part of the flash process itself.

However, programming errors from used or previously in-service ECUs with factory dealer tools are probably caused by the failure of the tool to update the VIN at the end of the programming session. Dealer tool writes the flash, then attempts to write the VIN. If the VIN write fails, it retries the entire programming process.

On global A vehicles (like this one), once the VIN is written into the ECM, or TCM, it cannot be changed unless the ECU is properly "removed" from the vehicle.

As far as I know, all T87As are interchangeable.

[jaketillmann86]

We weren?t trying to change anything about the ecm though. We were simply using it as a surrogate to try to load a different OS into the TCM.

The MDI read the ecm correctly, but when we tried to work through the pass through programming windows it threw an error code after selecting ?replace transmission? or ?replace valve body?.

The tech didn?t seem very sure so there may be a simple solution. .

[IARLLC]

When I programmed new T87s in a 2015.5 Yukon Denali for use in a 2017 Silverado I also could not get SPS to allow a simple TCM program. I had to agree to program the PCM/TCM as a combination but when it came time for the solenoid info I input the info for the 2017 Silverado. It worked great.

As the other gentleman said that the T87 cannot work in a 2018... but you said a 2017 T87A worked in your 2018... and I have personally set up T87 to work in 2017s. Makes me wonder.

[jaketillmann86]

What particular option did you choose to do the combination programming?

I?m very green when it comes to GM programming interfaces. I have been considering buying a program tool and subscription, but I m afraid I will get off board programming errors since I do not run a BCM. Perhaps if I tell the dealer tech exactly what to do they can help.

[IARLLC]

In the old days if we could not change the VIN by choosing "reprogram" we could choose "replace and reprogram". On these newer rigs some modules (BCM, Radio, Instrument Panel) have let me change VIN just by writing in a different VIN and choosing "reprogram".

Back in 2018 when I did the T87s I think that I had to choose "reprogram" and PCM/TCM together. SPS threw the latest update in the PCM while we were at it then began the TCM programming according to the VIN of the 2015.5 Yukon Denali. When it came time for solenoid info I just input the info from the 2017 Silverado 8L90E sticker. I went ahead and ran it through the fastlearn process in the Yukon Denali since I was not sure if it would be possible in the much modified Silverado later. It all worked great. The Silverado was sometimes run in a restricter class so it was important to lower the shift points among other important changes for prolonged heavy throttle.

[sevinn]

Try disabling all brake sensor codes and see what happens. I've had some luck with that on a few setups.

[Camaro6]

You can always call GM SPS line for a special calibration. I've done that in the past and they give you a VCI number to use with SPS for the loading of whatever software they have available and compatible with your setup. You do have to complete a trans relearn with a scanner though once programmed, I had to. Also, any new module I install in a vehicle and program with SPS will not function until I do the trans learn. They sit in P or N as R or D does nothing and some older models will shift a few gears but that's it (lot drive).

[IARLLC]

You can always call GM SPS line for a special calibration. I've done that in the past and they give you a VCI number to use with SPS for the loading of whatever software they have available and compatible with your setup. You do have to complete a trans relearn with a scanner though once programmed, I had to. Also, any new module I install in a vehicle and program with SPS will not function until I do the trans learn. They sit in P or N as R or D does nothing and some older models will shift a few gears but that's it (lot drive).

I can confirm all of this but you might need to call the SPS line a few times to get a person who is knowledgeable enough and wants to actually help. They used to be a lot better to work with.

[jaketillmann86]

I was finally able to flash my 2018 TCM with 2017 OS using donor TCM and ECM from a 2017 Escalade. I sent my tcms and 2017 ecm to an off board programmer and he did a great job.

The TCM goes into gear with the 2017 OS, which confirms there was something about the 2018 OS that wasn?t jiving right with the swap. I suspect there is something different in 2018 OS that allows the TCM to see it isn?t in a stock vehicle and puts it in limp mode

Now sorting through some harsh shifting issues, but happy I finally have the correct solenoid info.

[IARLLC]

Thanks a lot for updating all of us. This will be helpful info going forward.

[ZBADESTZ]

Can someone help???

2018 ecu & tcu from sent the T87a to hptuners to unlock. I did the tcu swap feature in scanner under system tab. It works BUT everytime I shut off vehicle and restart it goes into limpmode and have to repeat process to get out off limp.

Any suggestions???

Thanks