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I pulled a file from a 2004 silverado 1500 that keeps burning clutches in the trans. The owner was wondering if this could be tune related possibly since the shift points seemed off. I noticed the gear and tire size didnt exactly match up with the vss sensor calibration in bluecat. Could this be the issue? I have attached the first read i pulled from the truck and also my file i made for the truck if anyone could look at these.
Go to the tune repository and compare it to a "like" stock setup. Can very easily be tune related, but on the 4l60's it was usually the input housing that killed the 3/4 clutches. It could also easily be a crack or something of that nature in the case itself. 60's were't the greatest...
I did do the stock compare, other than the speedometer calibration the only other changes were to the MBT timing table and the idle was raised to 795 on a stock truck. How exactly does MBT timing table come into play? I know it has some to do with predicted torque. I am more leaning to a poor rebuild, maybe they were replacing frictions but not fixing the true issue in the trans.
Pressure test the trans and compare to commanded pressure. I had a firebird that had been converted from auto to manual. I wanted the t56 and swapped it back to auto. Changed tune to auto and line pressure was always maxxed out at any rpm. Only way I fixed it was writing auto tune into PCM. This was before segment swaps, so those might work now. If pressure is good then rebuild would be questionable.
It has been replaced with a junk yard trans. I'd like to know if anything on the original tune file could have caused the issue. The truck has actually burnt 3 or 4 trans since the first tuner messed with it.
MBT is used for torque calculation, if the MBT is raised and the actual timing is much lower than MBT it will calculate less torque, the trans uses the torque value for line pressure.Quote:
Originally Posted by 04silverado6.0
There are tables that we cannot see for timing calculation and lambda calculation that relate to torque. The torque is calculated lower the further is is from MBT.
Honestly without driving the vehicle personally I can't point a finger per say, but I can say just from what I'm seeing tune 3 should be better for it simply because of the shift pressure increase and the slight decrease in shift time changes... The 3 degrees of timing wouldn't make any difference at all and honestly you should be able to run more than that and it last. The only questionable thing I saw were the TCC settings of the original tune - was it engaging and disengaging the TCC over and over? Or was it shifting from gear to gear a lot after tuning? VSS and gear settings being wrong will cause something like that on it's own, so possible there as well... Like I said though, without driving it and seeing how it's shifting with pedal and load input, hard to tell.
Actually hadn't even checked the MBT timing, just looked at the regular timing tables - 4wheelinls1 hit the nail on the head there - mbt was raised significantly which will cause lower trans hold pressures, so could be a culprit...
You need to log commanded force motor current to the transmission to determine whether the ECU is sending the correct pressure signal
and
You need to put a 0-300psi gauge on the transmission to determine whether the pump pressure of the transmission is keeping up with the commanded force motor duty current
This is the actual file i loaded onto the pcm. I set the shift pressure up a little different and lowered the shift times. I did not want to make large pressure or timing changes until we can get a day to do some data logging and driving. Thanks for the help, everyone.
Like I and kingtalon told you, test the pressure and log force motor or it's a guess. It's way easier and cheaper than pulling and rebuilding or replacing trans.