0411 Transmission Flaring - Tuning or Trans issue

[evilstuie]

Hey all,
I'm heading to the dyno in 2 weeks to get my project car tuned, its a SBC406 with AFR heads, HSR EFI intake, EX276HR cam, with a 0411PCM running it all with a stock 1997 4L60E, stock converter and 2.73 diff.

The tune LRT helped me with has been fantastic for idle and driving it around, there's a weird issue with a temporary bog-down and backfire spot, but that's not my issue.
My issue is when it is working nice, I'll put the foot down and the engine will rev great, but the transmission is flaring and not putting power to the back wheels.

I'm not sure what the transmission calibration is that was swapped in, but I'm wondering if there transmission calibration is for something meant to be a lot softer or slower changes etc, if someone can take a look.

The other issues I have that might/maybe affect it are:
* Possible vacuum leak causing the brakes to not work that great (could also be the issue with the backfire/bog down issue)
* Fuel sounds like it boiling back in the tank. After 20 minute drive the fuel is just bloating in the tank and you can hear it hissing and bubbling

Trans fluid is at correct level, there's no leaks or anything, and all gear changes are working and fast into gear at idle.

I just need to know if it's possibly a tuning issue or a problem with the trans before I lay out $1000 for a day of tuning to find the power won't transfer and they cant tune the engine under load.

https://i.imgur.com/FVOtqG9.gif (https://i.imgur.com/FVOtqG9.gif)

[lionelhutz]

Can you post the tune to look at?

How's the part throttle shifting? Good part throttle but WOT could mean the line pressure isn't high enough at WOT.

Did you put a line pressure gauge on it? I suspect you have to modify at the shift pressure or force motor tables but without a gauge you're just guessing.

[evilstuie]

Can you post the tune to look at?

How's the part throttle shifting? Good part throttle but WOT could mean the line pressure isn't high enough at WOT.

Did you put a line pressure gauge on it? I suspect you have to modify at the shift pressure or force motor tables but without a gauge you're just guessing.

Here's the tune file.

I haven't got a line pressure gauge so haven't checked that yet.

[lionelhutz]

I was hoping to check the force motor current tables but they don't seem to be in the xdf.

When it is flaring? Just slips when driving?

If it's a shift flare then I would go after that shift pressure table first. You should be able to take it up to at least 90 and possibly to 96. 90 or 96 would give you the most line pressure possible without modifying the force motor current tables. Log the motor torque and see where you're torque wise during the shift. Then increase the table in that area. I expect it needs to be ramped up quicker to 90 or 96 as the final value. It also needs to plateau for the highest torque part of the table.

Also, drop at leas the 3-4 shift times to 0, possibly lower the other shift times as well and see how that helps.

[Hog]

Is it an actual flare, which is where the engine rpm increase during the shift, above the rpm at which the shift was initiated?
or
Is it a shift "bog", rpm drops properly during the shift, but the perception of an excessive decease in forward acceleration is evident.

If it is a "bog" and you are using an L31 calibration as a base in the 0411 PCM, the Torque Management could be an issue. The amount of Spark Advance removed is quite large, even more than in the newer 1999+ LM7 5.3 calibrations. IN stock type inductions/engines it can be especially noticeable at part throttle and downright annoying in modified configurations.

Doesn't entering "0" for shit times essentially eliminate the Adaptive Shifting strategies?

peace
Hog

[lionelhutz]

Yes, but adaptive shift is not torque management. Adaptive shift adjusts the line pressure during the shift.

[Hog]

I didn't suggest that disabling Adaptive Shifts was the same as TM

You recommended zeroing out the Shift Times, I'm assuming for diagnostics, and was attempting to follow your logic, which makes could help if its a shift flare..
Thanks

peace
Hog

[LRT]

....

[buddrow]

If you are running MAF, make sure it isnt contaiminated. Trans gets primary load information from MAF, if that data is skewed, youre screwed.

[lionelhutz]

Yes, increases in transmission pressure can be accomplished by tuning other tables, but only up to the pressure possible due to the lowest current in the force motor current table. So, altering the force motor tables can allow you to reach a higher maximum line pressure.

I posted to take the 3-4 shift to 0 and lower the time for the other gears.

The transmission tune still looks off, even without considering the torque calculation being off. Shifting 472 ft-lbs at 66% of full line pressure makes no sense. Just to compare, older PCM's for 300-350 ft-lb engines would pass that level at around 25% throttle at low speeds and 50-60% throttle at higher speeds.

At the dyno, they should be able to force the line pressure high so it won't slip and they can do the tuning. Then, either them or you can go back and do the transmission.

[LRT]

....

[lionelhutz]

#1. The transmission line pressure doesn't go from 0 to 96 psi. It goes from about 60 to 180 psi.

#2. The force motor current tables typically do not go down to 0A.

#3. Picking 96 "psi" in the tune tells the PCM to use the lowest force motor current, which is not 0A. So, lowering the table closer to 0A can increase the maximum line pressure.

#4. Suggesting to use a shift kit as the way to modify the line pressure makes little sense, because modifying the line pressure response to the force motor current really doesn't do anything different than ramping the currents in the table down to a lower final value to get a higher line pressure, until you do reach the limit of 0A.

The "psi" in the tune is just a number. The PCM uses the tables to pick a value from 0 to 96, and then goes to the force motor table and gets the current to apply to the force motor. So, the force motor current sets the actual line pressure.

I was just in a Canyon tune with a 3L 4-banger and the 3-4 shift pressure was 90 "psi" across the board and the shift times were all 0. The lowest force motor current was 100mA. So, suggesting the force motor currents could be lowered a bit or to use 0 time for the 3-4 shift just isn't that shocking...

[LRT]

....

[lionelhutz]

I'm not arguing, I'm posting facts.

4L60e line pressure:

When you force command the "line pressure" between 0 and 96 via software or a scanner, the ACTUAL transmission line pressure on a stock transmission should vary between about 50 to 180 psi.

https://www.atreman.com/wp-content/uploads/2016/04/4L60E-Checking-Line-Pressure.pdf


Also attached is a stock 2002 Camaro force motor table showing the usable part of the table reaching a minimum of 98, NOT 0. FYI, the tune NEVER uses the 100 column because those high current values would drop the line pressure to a very low value and cause bad slipping. I didn't do create this, so I have no idea why GM did it but the column is irrelevant anyways. The tables vary and usually go to 96 on older stuff. I have seen 0 in the highest or 96 column too, but the tune was limited to 90 "psi" so it NEVER used the 96 "psi" or 0A column.

[evilstuie]

To interupt the argument for a second.

I made the changes you suggested LRT, unfortunately I also got carried away and broke the cardinal rule of logic and changed some other stuff on the spark tables and speedo calibrations, which ran like crap and couldn't test the transmission state in anything other than idle basically.

When I got the car up to around 40km/h (maybe 15mph) and let off the throttle the transmissions felt like it was locking up and releasing over and over again for 0.5 seconds in succession until I put my foot back on the throttle.

Obviously the behaviour is bad, but is this a good sign that the transmission is ok and that I just need the tuner to calibrate / swap out the transmission segment, or is it a sign the transmission is faulty?

Also to throw it out there, is it possible the cause is that the transmission selector cable is not set properly and the trans could be between gears/engaging both?

[lionelhutz]

I'm just trying to post how the transmission works. The PSI stuff in the PCM is all labelled wrong since it's really more of a percentage where 0-96 is 0-100% of line pressure which is about 50psi to 180psi on a stock transmission. It's easier to setup the transmission when you actually understand what the PCM is doing. As for LRT, I can't help that he doesn't like being told he is wrong, but I'm not coddling him and letting him pass his wrong information as fact just to make sure his ego doesn't get bruised.

As for your transmission - either it was an internal issue or the PCM was rapidly shifting it between 1st and 2nd gear. At 0 throttle you have a 1mph spread in the shift speed. The speed has to go over 14mph to upshift and below 13mph to downshift. So, unless your speed signal was fluctuating by at least 1mph, the PCM should not have been rapidly shifting back and forth between gears.

You should be able to check the shifter cable by holding the shifter so the detent doesn't do anything and then moving the shifter so you feel where the transmission clicks in. For example, I have a floor shifter that can shift between N and OD without pressing the button. So, to check I hold the button and move the shifter to N and then release the button and try to move the shifter to R. It's adjusted right when the shifter just barely moves before hitting the stop in the shifter. I then checked OD and other gears a same way.

Overall, my feeling is that a big part of making an automatic vehicle fun for you to drive is tuning the transmission. On my stuff, I've probably done at least as many tunes for transmission shifting compared to engine tuning. On my pickup, I licensed it with HP tuners just to re-tune the transmission.

And you should pick-up a line pressure gauge if you want to be verifying the transmission is OK and also tuning it. It's a similar importance as using a wideband for the engine.