3rd Gear TCC locking/unlocking issue

[1BadAction]

I have my trans tune very close to where I want it, holds 3rd with TCC locked up to 47mph then shifts to OD/Locked. The issue comes in at 3rd gear in traffic when I let off the gas, the TCC unlocks, then locks back up again when I put my foot back on the gas. PWM has been hydraulically eliminated and the TC is a 3200 Circle D, so it gets annoying, not to mention the excess wear this causes. I want it to stay locked when I am at 0% throttle and the TCC lockup tables reflect this, am I missing something else that causes it to unlock? Vehicle is a 2003 4.8L GMC Sierra.

[1BadAction]

Tune, if anyone wants to take a look.

13779

[joecar]

If the tune file originated from a truck then it will do that...


the car tunes kept the TCC locked on zero throttle (F-car and Y-car).

[1BadAction]

Any way that I can fix it?

[ScarabEpic22]

Can you seg swap a car trans segment? The only way that this can be fixed is to run a car TCM OS/trans seg, works really well though!

[joecar]

You will need a car trans segment from a file with the same OS as your file...

[1BadAction]

Doesn't appear that I will be able to make it work. OS 12579405

[joecar]

You would have to do something like this:

change your OS to 12212156 from a Camaro/Firebird (auto trans), and manually copy all your tables over.

[ScarabEpic22]

The problem with that is that its an 03, not an 02 so its DBW and a 1MB PCM not 512kb PCM.

[joecar]

Ah... so then it's not doable... ( I failed to see the small detail, sorry )

(I have no idea if the GTO keeps the TCC locked on zero throttle, let alone a matching OS id).

[Taz]

Doesn't appear that I will be able to make it work. OS 12579405

Upgrade to 2004 truck OS 12587603. You will need to adjust the injector tables - your 2003 truck still uses a fuel return line and fuel rail mounted pressure regulator. 2004+ moved to a returnless system.

Then swap in the transmission segments from a 2004 Corvette A4 with the same OS (12587603).


Regards,
Taz

[1BadAction]

Upgrade to 2004 truck OS 12587603. You will need to adjust the injector tables - your 2003 truck still uses a fuel return line and fuel rail mounted pressure regulator. 2004+ moved to a returnless system.

Then swap in the transmission segments from a 2004 Corvette A4 with the same OS (12587603).


Regards,
Taz

Awesome, this sounds like a plan. Thanks guys.

[joecar]

Cool :cheers:

[1BadAction]

13808

[1BadAction]

No going back now...

[1BadAction]

Up and running based on the suggestion from TAZ (thank you sir!), truck ran fine but felt like I was towing 3000lbs. Besides the inj tables he mentioned, almost ALL of the other fueling tables are different stock V stock, PE mode especially. So for anyone else doing this, make sure you go through all of the engine calibration tables with a fine tooth comb.

[1BadAction]

Now it's taking a bit longer to crank than it did before. ugh... Any suggestions?

[1BadAction]

Now it's taking a bit longer to crank than it did before. ugh... Any suggestions?

Never figured out this issue, but another issue that came up is the "anti-clunk" clunk reduction built into the engine OS that holds a bit of throttle as you come to a stop. There's no way to turn it off or modify it, and I will not deal with a truck pushing me through a stop light like my TBSS did with it's stock tune. It was a good experiment but I ended up going back to the original OS.

[Taz]

No such thing as a "free lunch" is there ?

Sometimes changing the OS will require a touch up to the VE & MAF tables - not a problem as long as the injector data is accurate. With a WBO and a free morning this is quickly sorted out.

This should address the longer cranking you described. If not, and the engine starts better with the throttle opened slightly - then add some airflow via B0102.

The "push" when coming to a stop and the "anti-clunk" you described can be tuned out via B4307 - the airflow will need to be reduced. Do this in small increments until the vehicle acts the way you prefer.

A little extra work - but in the end the vehicle should run like it came from the factory - just depends on your comfort level with the software, and how much effort you are willing to expend to keep the TC locked while coasting.


Regards,
Taz

[1BadAction]

No free lunch for sure, lol... I will be working on my WB02 installation this afternoon and getting it sorted out, then try again. I've been looking for an excuse to start working with lean cruise also, hopefully I can pick up a bit of MPG.