Unlocked T87A shift schedule in 8L90E help

[voodoo tuner]

Hello Guys , i have unlocked T87A TCM from HPT

The car is 2017 GMC Sierra 1500 Denali 6.2 8L90E

I did all the TCM Swap instruction Process that comes from HPT

And everything seems OK , but in ( L ) when i try to upshift from 2-3 , 3-4 , 4-5 ?.Etc

It shift automatically not manually what do i have to change on the Tune to Figure this up ?

Best regards.

[voodoo tuner]

Up still no on can help ?

[TransGo Robert]

I am a transmsision guy so I most likely won't be able to help with the tuning side, but if you don't at least post your tune on here nobody can help you that's for sure. A log of it recording when it does not do what you want might also be helpful, but the tune is an absolute must.

[voodoo tuner]

Attached the tune and full WOT pull in L , it shift manually from 1-2 2-3 , but from 3-4 4-5 it shift automatically

[TransGo Robert]

Attached the tune and full WOT pull in L , it shift manually from 1-2 2-3 , but from 3-4 4-5 it shift automatically

I really don't know enough about tuning to know why shows that, but I noticed that your PRNDL Status PID goes to unknown: 82 or 81 when you put it in tap shift mode, and the transmission shift mode says Normal which does not make sense to me. I would expect it to say Pattern A or Patern B, but may be I am wrong. Also I see what you have your full throttle TUTD set at, but the log does not include speed in mph so I can't tell if it is exceeding what you have in that table or not for the shifts that shift automatically. Maybe the numbers in the tables that I put in a red box need to be higher, I don't know if you are reaching those speeds or not but I would think so at WOT.
Log.png

[voodoo tuner]

I really don't know enough about tuning to know why shows that, but I noticed that your PRNDL Status PID goes to unknown: 82 or 81 when you put it in tap shift mode, and the transmission shift mode says Normal which does not make sense to me. I would expect it to say Pattern A or Patern B, but may be I am wrong. Also I see what you have your full throttle TUTD set at, but the log does not include speed in mph so I can't tell if it is exceeding what you have in that table or not for the shifts that shift automatically. Maybe the numbers in the tables that I put in a red box need to be higher, I don't know if you are reaching those speeds or not but I would think so at WOT.
Log.png

Attached full WOT pull with Speedo

[TransGo Robert]

Attached full WOT pull with Speedo

Yup, that's the problem. It shifts 4-5 exactly at 81 mph and 5-6 at 99 mph. Just raise those numbers in that table and it will do what you want.

[voodoo tuner]

Yup, that's the problem. It shifts 4-5 exactly at 81 mph and 5-6 at 99 mph. Just raise those numbers in that table and it will do what you want.

Unfortunately i did that and re run it and the same thing is there

[voodoo tuner]

BTW in first i was doing Write calibration and there’s no Tune Change applied to the Truck after that i use Write entire then it applied the tune

[TransGo Robert]

Unfortunately i did that and re run it and the same thing is there

There must be another table that is wrong in there somewhere then or it has to do with that PRNDL PID that is not reading right. Post your new tune and a new log with the new tune and lets see if we can figure out what is still causing this and what if any difference the changes you made did.

[TransGo Robert]

BTW in first i was doing Write calibration and there’s no Tune Change applied to the Truck after that i use Write entire then it applied the tune

Sorry that went right over my head, I have very little experience with tuning so not sure what that meant. 99% of the time I look at logs guys take to help them figure out their transmsision issue, the tuning stuff I just about never deal with unfortunately.

[voodoo tuner]

There must be another table that is wrong in there somewhere then or it has to do with that PRNDL PID that is not reading right. Post your new tune and a new log with the new tune and lets see if we can figure out what is still causing this and what if any difference the changes you made did.

The last log after doing the last change on the TUTD , Is still doing PRNDL Status unknown .82 and 81 in D and L , so changing TUTD speeds doesn’t fix that because the TCM doesn’t know if i’m in D or L position

[TransGo Robert]

The last log after doing the last change on the TUTD , Is still doing PRNDL Status unknown .82 and 81 in D and L , so changing TUTD speeds doesn’t fix that because the TCM doesn’t know if i’m in D or L position

Yea it definitely won't fix that. Don't know if it is an HP Tuner issue or if the computer really does not know what range the shifter is in, but if it really does not know then that definitely could be the issue I would think. But why would it work ok for the 1-2 and 2-3....? It sounds much more like a table issue, on top of it that it was shifting previously exactly at the mph listed in your table for those shifts that happen before reaching the max RPM you have it set at for the shifts.

[voodoo tuner]

Yea it definitely won't fix that. Don't know if it is an HP Tuner issue or if the computer really does not know what range the shifter is in, but if it really does not know then that definitely could be the issue I would think. But why would it work ok for the 1-2 and 2-3....? It sounds much more like a table issue, on top of it that it was shifting previously exactly at the mph listed in your table for those shifts that happen before reaching the max RPM you have it set at for the shifts.

After asking many people, the issue with the Trucks they don’t have Driving mods on them , so even if you put it in L it still doing Auto shifting from 3-4 and above , specially in the 1-2 & 2-3 it reach the RPM Cutoff that you’re tuned for , but from 2-3 the cutoff sets on Stock RPM ( 5500 rpm )

Basically it feels like you're just Tuning the First 2 gears after that it’s doing like the stock tune even if you Change the TUTD Speedo shift time

[TransGo Robert]

After asking many people, the issue with the Trucks they don’t have Driving mods on them , so even if you put it in L it still doing Auto shifting from 3-4 and above , specially in the 1-2 & 2-3 it reach the RPM Cutoff that you’re tuned for , but from 2-3 the cutoff sets on Stock RPM ( 5500 rpm )

Basically it feels like you're just Tuning the First 2 gears after that it’s doing like the stock tune even if you Change the TUTD Speedo shift time

That really makes very little sense. You have the a 1-2 shift at 5820 rpm, 2-3 at 6083, 3-4 at 5734, 4-5 at 5513 on the first run, then 5909 - 5640 - 5809 - 5523 so obviously it is not set for a 5500 cutoff and it is not consistent either, the only thing constant was the road speed adn it matched your settings in your tune when you posted it. You never sent the update tune or log so we can't make any headway, but I don't buy this factory cutoff theory for one bit. Whoever told you that should come on here and explain how that is possible, how it works, and how it would be that it cannot be changed with tuning? Then I might understand and agree, but until then, I have to call BS on the claim.

[voodoo tuner]

That really makes very little sense. You have the a 1-2 shift at 5820 rpm, 2-3 at 6083, 3-4 at 5734, 4-5 at 5513 on the first run, then 5909 - 5640 - 5809 - 5523 so obviously it is not set for a 5500 cutoff and it is not consistent either, the only thing constant was the road speed adn it matched your settings in your tune when you posted it. You never sent the update tune or log so we can't make any headway, but I don't buy this factory cutoff theory for one bit. Whoever told you that should come on here and explain how that is possible, how it works, and how it would be that it cannot be changed with tuning? Then I might understand and agree, but until then, I have to call BS on the claim.

as i'm checking the TUTD shift RPM it shows different than the Actual RPM that it Reaching in the Log on all of the shifts


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attached the last tune with the TUTD speed table change

[TransGo Robert]

as i'm checking the TUTD shift RPM it shows different than the Actual RPM that it Reaching in the Log on all of the shifts


Capture k.PNG

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attached the last tune with the TUTD speed table change

I think it is normal to overshoot by a couple of hundred RPMS like that, it depends on how fast the shift occurs after it is commanded. I see you have the 4-5 200 RPM lower, so you might want to put that at 5800 as well. In the other table where you made the changes, I am wondering if you don't also have to ramp up the doshifts above it to make it shift at the right time. I wish others with more tuning experience would chime in, that's really quite a bit outside my comfort zone, I know just enough about Tuning to be dangerous.

[voodoo tuner]

I think it is normal to overshoot by a couple of hundred RPMS like that, it depends on how fast the shift occurs after it is commanded. I see you have the 4-5 200 RPM lower, so you might want to put that at 5800 as well. In the other table where you made the changes, I am wondering if you don't also have to ramp up the doshifts above it to make it shift at the right time. I wish others with more tuning experience would chime in, that's really quite a bit outside my comfort zone, I know just enough about Tuning to be dangerous.

Adding or pulling RPM’s i don’t think it’s a commanded Table to let the TCM give you the ability to Trigger shifting by yourself

Because think about that just for a second, if the table is setup from 2-3 at let’s say 5800rpm when I Reach that RPM it doesn’t stay there and cutoff or bounce the limiter , it shift to the next gear without letting you shift it manually

I want to pull this command from the TCM to not give him the ability to Shift to any Gear when it’s in L

[TransGo Robert]

Adding or pulling RPM’s i don’t think it’s a commanded Table to let the TCM give you the ability to Trigger shifting by yourself

Because think about that just for a second, if the table is setup from 2-3 at let’s say 5800rpm when I Reach that RPM it doesn’t stay there and cutoff or bounce the limiter , it shift to the next gear without letting you shift it manually

I want to pull this command from the TCM to not give him the ability to Shift to any Gear when it’s in L

When you set the RPM limit that's when it overrides you and upshift it to prevent damage to the engine. Many guys use that to set it so that when they go on the track they just put it in TUTD, floor it and let it shift at precisely the RPM they want it to shift at. Then when driving normal on the road they put in OD range and now the shifts are back to being normal instead of going way up like they need on the track. If you want to make sure it never shifts unless you deice then you have to put all those RPM and MPH numbers up to something not physically achievable.

[voodoo tuner]

When you set the RPM limit that's when it overrides you and upshift it to prevent damage to the engine. Many guys use that to set it so that when they go on the track they just put it in TUTD, floor it and let it shift at precisely the RPM they want it to shift at. Then when driving normal on the road they put in OD range and now the shifts are back to being normal instead of going way up like they need on the track. If you want to make sure it never shifts unless you deice then you have to put all those RPM and MPH numbers up to something not physically achievable.

i get what do you mean , but my request is different than what those Guys Are doing at the track

Bottom Line i want to Cancel " Auto Shifting " when the gear is in L

so i tried multiple changes on the tables and i manage to hold every Gear to the Rev Limiter without the TCM doing Auto shifting , But it Stuck in Rev Limiter and Refuse to shift up if i Tap Up

what i did is this :

Shift Scheduling > Full Throttle Shift RPM > Normal " rising all the RPM's to 6300 "

Shift Scheduling > Full Throttle Shift RPM > Pattern A " rising all the RPM's to 6300 "

Shift Scheduling > Full Throttle Shift RPM > Pattern B " rising all the RPM's to 6300 "

Shift Scheduling > Full Throttle Shift RPM > Tap Up / Tap Down " rising all the RPM's to 6300 "

So I called A Local Tuner and He told me to did this changes :

Shift Scheduling > Full Throttle Shift RPM > Normal " set all the RPM's to 5800 "

Shift Scheduling > Full Throttle Shift RPM > Pattern A " set all the RPM's to 5800 "

Shift Scheduling > Full Throttle Shift RPM > Pattern B " set all the RPM's to 5800 "

Shift Scheduling > Full Throttle Shift RPM > Tap Up / Tap Down " rising all the RPM's to 8k "

and what happened ? nothing it Return to do the AUTO SHIFTING again in L