TCC unlocking while coasting

[forcefedjunkie]

Is there a way to prevent this in 4th gear? I have a Precision 2800 stall and it has a very harsh lockup. Whenever I let off the gas in 4th gear, irregardless of speed, the TCC unlocks and then I have to deal with the lock-up again shortly after. This is in a Trailblazer SS by the way.

My 2005 GTO does not do this, the TCC stays locked until I reach a speed/rpm where it is programmed to unlock. I cannot find a difference to account for this in the tables I've looked at.

Unrelated question, I keep seeing "Set max to 100, min to 90" while searching posts concerning the TCC, what is this referring to? TIA.

Todd

[jimmyblue]

Log it and watch for TCC_MODE to show you a -3- when
it unlocks. If this happens (you have to wtch it real time
in the table display, it will not graph or export properly
last I looked) then you are having misfire detects at
decel. Verify this by the Misfire Current Cylinder 1-8 PIDs.
Anything at all there will unlock the converter temporarily.

In your TCC lockup MPH table, at low TPS, do you have
a 255MPH value? Some cals do this to make the vehicle
freewheel rather than engine-brake. Depends on what
you like, for that.

Min/Max refers to TCC Duty Cycle, trying to eliminate
the soft (PWM) apply that makes for excess slip on
light throttle (along with stock tune starving the entire
trans at low TPS, another story).

[forcefedjunkie]

Both the 4th gear apply and release have values in the upper/lower 30's.

I'll check for misfires.

Could there be a command that releases the TCC when absolute TPS hits "0"?
The instant the throttle is released the TCC mode goes to unlocked.

[forcefedjunkie]

I am seeing no misfires on the individual cylinders when the throttle is released. TCC_mode only shows "off" or "locked on". There are no values like 0,3, or 7.

Later I'll post a picture of the TCC lock-up table. It's not too much different than stock though.

Todd

[Chris@HPTuners]

i fixed up the scanner in the latest beta to get rid off the numbers

i don't know if there is a parameter to control the release in this case but i will put it on my to do list.

Chris...

[Bandit gs]

i fixed up the scanner in the latest beta to get rid off the numbers

i don't know if there is a parameter to control the release in this case but i will put it on my to do list.

Chris...

Please do, i have this same problem in my 98 buick with a yank stall, it drives me insane, i've tried everything.

[forcefedjunkie]

i fixed up the scanner in the latest beta to get rid off the numbers

i don't know if there is a parameter to control the release in this case but i will put it on my to do list.

Chris...

I did a little more research on this and confirmed that there is something in the code for these trucks (Trailblazer SS) that controls this. At least one tuner claims to have a method of defeating this although this parameter is not currently accessable through HP Tuners.

Todd

[forcefedjunkie]

I think the key is accessing something called TCC Decel constants. I don't believe these are currently accessable. There are many Trailblazer SS guys having the same issues as me with aftermarket torque converters. Unlike the GTO our PCM code unlocks the TCC as soon as the throttle is lifted. I'm sure many people would appreciate access to this table.

Todd

[blown3qtr]

I am having the same issue.

[keith42]

was this issue ever fixed?