my torque converter is a wimp

[LB72004]

anyone have trouble with their torque converter not locking or coming unlocked often during normal driving and cruising?

this is on a 6th speed allison, 2008 LMM 3500HD dually. everything is stock except the tires at 245/75/17, DPF delete and my tuning.

the problem i am having is that it does not like to lock the converter. even when lightly cruising around town or on the highway it will not lock on its own. if i play with the accelerator i can get it to lock but the slightest increase or decrease in the pedal will unlock it. when in cruise control it will not lock at all unless i take it off of CC and play with the pedal to get it to lock then hold it while engaging CC. it then seems that it will hold the converter locked through light grades but will instantly unlock it if it slightly more gradient or on all down hills.

i am not even trying to get it lock under power just daily driving and it seems like it is scared to do it.

i have tried lowering the TCC lock speed to less than the shift speed and also above it. tried it at various MPH settings, etc. D5074 on and off, adjusted ramp rate, minimum & maximum duty cycles, raised the slip inhibit to max and it behaves the same.

driving down the highway going 65 and just over 2000 rpms sucks, especially for MPG

any ideas on what to look for or change to raise the converters confidence?

if needed i can upload the tune

thanks Jason

[joecar]

I am not familiar with Allison... but the various TSTATE pids may provide you with the reason why the TCM is unlocking the TCC... maybe.

[LB72004]

thanks, i have yet to log it. i think that is what i will do today

[THEFERMANATOR]

Whose tuning? The MAJORITY of trans issues goes back to ECM tuning. If you get to wild with the torque based tables from stock, the TCM can do what your describing. If in doubt, go back to stock and see if it still does it. If it does you may have a problem with the stator shaft in the trans. It is known issue that GM released a bulleting for. Also you should note that it isn't hard to destroy the clutch lining in a stock converter, it only has to be slipped a few times before it's gone. And in the 6 speed's the converter seems to be the weak link.

[LB72004]

thanks Ferm, I fear that it may be a spun stator shaft. after reading up on the symptoms and what others are experiencing it looks an awful lot like a spun shaft.

it seems that it will only lock under light throttle and when i let all of the way out and carefully apply re-apply the throttle. otherwise it will never lock

the tuning is mine but it does appear that someone else may have been in there before me or perhaps a canned tuner as the DPF was deleted when i purchased it. the only changes that i could see other than the DPF stuff was that the torque base table was extended out just a little. looked like maybe a tow tune

the transmission seemed to have no changes other than the some torque limiters and curiously the TCC max duty cycle was raised to 95%. perhaps trying to fix a problem???

so do you think i should log TCC commanded lock and slip or is there more? haven't realy done any transmission logging before

thanks Jason

[THEFERMANATOR]

thanks Ferm, I fear that it may be a spun stator shaft. after reading up on the symptoms and what others are experiencing it looks an awful lot like a spun shaft.

it seems that it will only lock under light throttle and when i let all of the way out and carefully apply re-apply the throttle. otherwise it will never lock

the tuning is mine but it does appear that someone else may have been in there before me or perhaps a canned tuner as the DPF was deleted when i purchased it. the only changes that i could see other than the DPF stuff was that the torque base table was extended out just a little. looked like maybe a tow tune

the transmission seemed to have no changes other than the some torque limiters and curiously the TCC max duty cycle was raised to 95%. perhaps trying to fix a problem???

so do you think i should log TCC commanded lock and slip or is there more? haven't realy done any transmission logging before

thanks Jason

Raising the duty cycle is a HUGE no no with a 6 speed, and should never be done. Sure sounds like it had a bullydog or something else like that on it. I have tuned a few trucks that had them on them, and the changes weren't always visible in the tuning as they used custom operating systems for there tune files for the change on the fly tuning they had.

[LB72004]

Hmm, guess i should find an unmolested ECM and TCM stock tune and start from there.

i believe i can find the ECM file. do you know where i can find a TCM file calibration #25836826 or perhaps if there is a better calibration?

do you know of an easy way to check for a spun stator shaft? i read on another forum that you can remove the "from cooler" line and see if the fluid drains out of the transmission, another forum said that the only way to tell was to pull the transmission and inspect the shaft

[THEFERMANATOR]

The ONLY way to tell is to pull the trans out and inspect the stator shaft. They will ALL drain out the cooler lines if you leave the lines out of the cooler, or if you pull the pan off and the filter out. As for stock tune's, I don't have any LMM reads. Maybe try duramaxdiesels as I think there are a few reads over there. The only way to do a full flash would be if you could obtain a full read. Last I heard, we were still limited to calibration reads only at this time. Unless you have an A50, but if you have an A50 you can't edit the file, so I know you have an A40/A46 now as you said you have edited it.

[LB72004]

Well I did some logging today. Just some light in town driving nothing to hard. Never saw more then 25 rpm tcc slip with it locked and it still kicked out when I lightly pressed on the accelerator. It still doesn't lock unless I go to 0% throttle then back. Going to make some changes to the tcm tune tomorrow to see how it responds

[LB72004]

anyone here have a stock A40 TCM full read that they can send me? i am looking for OS #25836826 (unless it is known that there is a better one to run).