Transmission Slipping or Tune Issue?

[MarkTucker]

Looking for help on a car that I believe the transmission is slipping on. Transmission was rebuilt by a local transmission shop and then they installed a 3500 stall converter and had another local shop do some motor work. Then I am helping the guy tune the car for all of him mods.

I used Bluecat to set up the shift speeds and auto tcc tables. I bumped shift pressure up some from stock values, shortened shift times, bumped tcc apply table from 5 - 400 (positive) rpm up by 10%. And put the regulator offset to 90psi (read on a HPT thread as a recommended set point for higher stall converters).

As you see in the log, i get a flare (slip) on shifts.

How do i determine if this is a tune issue or a mechanical issue?

I initially bumped shift pressures up only 10%, then was having this issue which felt like to low of pressure. So I bumped the shift pressure up quick a bit more to see if it helped any, and it didn't.

This is only part throttle shifts, I have yet to do any WOT shifts yet to see if the slip is still present or any worse? Should I try to see how WOT shifts are?

Thank you very much,

[5FDP]

In my eyes, too much TM stuff was messed with but that's just me.

Increase you shifts times back to where you first had them and work with your on-coming pressure presets more. Those along with your shift speed settings should help you get cleaner/quicker shifts on the 6L80e's. I'm not sure how quick they make the shift time torque adder tables from the factory, though I've seen G8 tunes around .2000-.2500 depending on gear.


You can also reduce the shift torque factor by 10-15% and you should be fine. Somewhere around .8600-.9000 is where I run them.

[MarkTucker]

Thank you very much, I will post back with a update.

[5FDP]

I forgot to say it before but if you make any pressure changes or on-coming preset changes you need to reset the presets in the transmission before you drive it. Do that in the VCM scanner functions after you flash the tune and before you start the car. Otherwise the changes won't completely take.

[MarkTucker]

Something mechanical must be wrong with the transmission. I originally disabled the Transmission torque management because during shifts it was pull so much timing and just bog the car down (keeping it from slipping the transmission). So I disabled the torque management to see what it would actually be doing if it wasn't pulling the timing out. And sure enough it would just flare up (slip) on shifts.

But it was originally doing this on stock transmission file when delivered to the guy to do the engine work, just thought it was the high stall converter causing this. So from the help of your information and another local tuner that is very familiar with the 6L80 transmissions in these Camaro's. Nothing has made the issue better.

So thank you very much for all the help.

But I do believe that something was not done correctly when the transmission was assembled. I also had another local transmission shop owner go in a ride with me and explain everything I have done. And he says he feels like it is bleeding/leaking pressure. He said we would need to put a mechanical gauge on to see what actual pressures are. As I can only see what commanded pressures should be.

[SSUte01]

Sounds patronising, but how's the fluid level?

[mbray01]

did you clear all adapts, clear fast learns, and re-perform fast learns.

I have seen a few trans condemned when actually nothing was wrong, it just needed the fast learn performed

[MarkTucker]

Sounds patronising, but how's the fluid level?

I did check fluid level. It was full. That was actually the first thing I checked once I felt the issue. And was told of the previous work.

[MarkTucker]

did you clear all adapts, clear fast learns, and re-perform fast learns.

I have seen a few trans condemned when actually nothing was wrong, it just needed the fast learn performed

Yes, I did clear adapts and fast learn and perform fast learn. I did not at first when I noticed the issue, but was asked to try that when I contact another local tuner. So I did it and still didn't help.

Thank you