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).

[LB72004]

so i think i figured out why the TCC wont lock when in cruise control. doing some testing i found if i had the TCC release set to unlock at 0% throttle to enhance coasting it would not allow the TCC to lock unless i played with the peddle first and got it to lock then engaged CC. it would still kick out at the slightest hill though. quite a bit different behavior than the 5 speed. my 5 speed will do what i tell it to do. this one seems like a guessing game

need to do some more testing and tune adjusting as i still doesnt want to lock while accelerating.

i currently have the TCC lock set to 1 MPH less than the upshift. thinking that the TCC should stay locked the whole time in gear but it doesnt.

[asmithIII]

How did you log tcc slip?
I believe that tcm OS is in my 08 and I'll post a stock version for you.

[LB72004]

thanks, just make sure it is a full read. i hear it may take about an hour or so to read the full OS

the scan tool has a pid for TCC slip that shows it in RPM. it is just reading the RPM before and after and subtracting the after RPM from the before RPM. i also monitor the TCC PSI to see when it is locked then look at the RPM for slip, otherwise it will show lots of slip with it unlocked, so you need to see when it is locked.

the biggest problem i am having with logging the transmission is i cant get any of the speed (VSS) pids to work. makes it harder to understand what it is doing when you cant reference the logged data to any MPH

[LB72004]

anyone want to look over this log and give me input

still doesn't lock reliably but once it is locked it seems to stay locked much better then before.

thanks Jason

[asmithIII]

My OS is 25836826

If possible, I'll try a full scan. Any advice in doing a full read of the TCM would be appreciated.

[THEFERMANATOR]

Full reads of A40's aren't available yet. I believe full reads of A50's is, but A40's wasn't last I checked. I know a friend of mine tried this with the latest release, and ended up going to GM and having his new TCM flashed as he couldn't get a full read.

[LB72004]

According to this it sure seems like it is supported.

http://www.efilive.com/latest/al5-a40-a50-allison5-6-speed-transmission-support/

Unless I am mistaken, it seems that back in June of this year full flashing was added in an update

[LB72004]

so after reviewing my logs it seems that i am running into the infamous 600 RPM slip limit. somewhat embarrassing, should have seen this sooner

[LB72004]

ok, maybe not. now it looks more like it is related to throttle position. i don't know, i'm confused...

[THEFERMANATOR]

According to this it sure seems like it is supported.

http://www.efilive.com/latest/al5-a40-a50-allison5-6-speed-transmission-support/

Unless I am mistaken, it seems that back in June of this year full flashing was added in an update

The last paragraph,

Full flashing support for the 2006-2009 A40 Transmission has also been added to this release. This feature is ONLY available in EFILive V8 Scan and Tune software and is a free update for existing customers. Stay tuned for further updates because over the coming months we plan to modify the read options for the A40 TCM to allow both the current option of a calibration only read, and a new option to 'read entire.'

They do NOT currently offer full reads, only cal reads like they have been doing. Full reads take up to an hour for the A40/A46. They DO offer full flash capability IF you can obtain a full read using 3rd party software. The link only says they have full reads for the A50 which is mid 09+. And will be adding soon the option for full and cal reads for the A40 in the future.

[LB72004]

Snap

Well I guess I will just have to play with what I got and wait or take it into the dealer

[asmithIII]

I looked at log

did some math

found that clutch pressure muliplied by TCC Maximum gives TCC Commanded pressure

I have been told that changing TCC Maximum is a no no but can't understand why.

Seems like that an increase would help lock the torque converter. I know that a reduction does increase slip...tried that and in another trial, an increase stopped my torque converter slipping.

Trying to log my own data is not going well. PID's are not supported. Did you use EFI Live and what version?

Thanks

[LB72004]

I am using version 7.5.7. make sure you have the right controler (TCM) selected and then click the button for "check support for each pid" or Shift + F2.

from what i have gathered the 65.62% in the max duty cycle is the max the solenoid can safely take and is the max pressure that will be delivered. raising it above that only risks solenoid damage without any pressure increase. the tech 2 will show it at 100% while Efi Live shows it at 65.62%. 65.62% is max pressure.

[THEFERMANATOR]

I looked at log

did some math

found that clutch pressure muliplied by TCC Maximum gives TCC Commanded pressure

I have been told that changing TCC Maximum is a no no but can't understand why.

Seems like that an increase would help lock the torque converter. I know that a reduction does increase slip...tried that and in another trial, an increase stopped my torque converter slipping.

Trying to log my own data is not going well. PID's are not supported. Did you use EFI Live and what version?

Thanks

In a 6 speed you do not up the TCC solenoid duty cycle because where it is set at for a max IS 100% duty cycle. The 6 speeds changed solenoids fro mthe 5 speeds, and the new solenoid requires a lower duty cycle to avoid over saturation of the coil and burning it up. MANY have upped it thinking that more is better, and it doesn't take long before your F solenoid fails due to over current.

[asmithIII]

Finally logged TCC pressure data

Increasing the TCC solenoid duty cycle is not useful in raising the pressure to the TCC. Increased duty cycle did not increase the pressure. Decreasing the duty cycle does lower the TCC pressure.

Thanks for all the help.

[LB72004]

so i decided to try out my triple disc torque converter from my build 5 speed transmission in my lb7. dropped my 5 speed and took out the TCC. then i dropped the 6 speed and swapped them out. wow what a chore. :Throwup: dont ever try this in your driveway without some extra help

the torque converter is definitely tighter and drives much better but the TCC still locks the same, or should i say doesn't lock the same. still seems that if the slip is above say 100 rpms or so it will not lock. :wallbash:

i am starting to consider wiring up a lock switch. question for you allison gurus. i know the 5 speed cant lock the converter in 1st but how about the 6 speed? not trying to lock it in 1st but if i build my own locking switch and forget it turn it off...

[THEFERMANATOR]

Yes, a 6 speed can lock in 1st. Also wiring in al ockup switch can piss the TCM off in a hurry, so you have to be creative in how you make it.

[LB72004]

I understand. I was just thinking of just wiring up a momentary push button that i could push to get it to lock then once it is locked it should take over as the slip would be low enough that the tcm will alow it.

If i need to i can rig up some relays and a resistor to keep the tcm happy but i am hopping that a momentary manual activation of the solenoid wont freak ot out

[LB72004]

while going over my TCM tune looking for any reason why my TCC doesn't like to lock and the D5231 TCC Apply Slip Inhibit maximum value started to seem odd to me. 8192 RPM??? why so high. is this carried over from the gas version? it seems awfully high to me. just over 8000 PRM, that is higher than the engine can ever rev. just looked out of place to me. dont get me wrong, i like the extra buffer it provides but 8K.

so this is what i did. lowered it to something more sane. plugged in 2000 and gave it a spin. ya, looks like it worked. i could feel it lock while accelerating. feels a little hard in the slower speed slower gear range so i will go back and lower the minimum duty cycle till it locks good

so, what do you guys have for your D5231 TCC Apply Slip Inhibit value. have any of you had this problem?