6 Spd upshift torque reduction

[HTMtrSprt]

I've got a 2007 LMM Duramax with an exhaust and a mild tune -I've turned off the tq reduction request option in the trans tune which made it shift much better HOWEVER, monitoring "driver demanded torque" and "torque delivered to trans" still shows a reduction of 50-60 ft/lbs in delivered torque when it makes a shift.... you can clearly feel it and it's annoying as hell. Is there any way to eliminate this?

[GMC-2002-Dmax]

Turning off the tq request is a bad idea, it could over time damage your trans.

You need to adjust the ecm tune to make it defuel less

[Wheelz]

You can also reduce the commanded shift time (or bump shift pressure if you turned the learning shift time feature off) for that shift, which is my personal preference. You can get some nice crisp shifts outta the stock hardware balancing TR and shift time/pressure.

[HTMtrSprt]

I already have firmed up the shifts by reducing the desired shift times and we are looking at installing a TransGo JR shift kit HOWEVER, regardless of how nicely the trans shifts, there is still the matter of the VERY annoying power reduction during the shift. This HAS to come as a request from the trans controller to the engine controller and since I have turned off this request in the trans program, there should be no such reduction in power while shifting.... UNLESS there is still another parameter in the program which we do not have access to. Anyone (Paul Blackmore) have any thoughts on this????

[ScarabEpic22]

As stated in post 2, have you disabled defuel in the ECM?

[HTMtrSprt]

I have removed every limit I can find in the trans AND engine program.... what parameter specifically is "defuel"?

[ScarabEpic22]

Ok, you didnt say that before. Defueling is related to max torque values, if there is a table/parameter that isnt set correctly it will limit the TQ output. I havent done much work with the Allison side, but the ECM has a lot of tables related to TQ control.

Post your current tunes and stock tunes (ECM+TCM), usually it's something small that gets overlooked.

[HTMtrSprt]

I know....I've gone through them all and every torque limit in the trans program (including tq/throttle pos) exceeds the tq values set/produced in the engine program. Since the truck, under light accel, lays over BEFORE starting the shift, and the engine program has no way of knowing when a shift is about to occur, the reduction HAS to come about because of a requested tq limit from the trans controller to the engine controller. For instance, during normal accel from a stop, "driver demanded torque" shows 340 ft/lbs as does "delivered torque to transmission" right up until the shift when "delivered torque" drops to 285 ft/lbs during the shift and then returns to match "demanded torque" after the shift.

[THEFERMANATOR]

Word of caution to others reading this, disabling the defuel on shifts is HIGHLY NOT RECCOMENDED. And is a GOOD recipe for grenading your trans. This isn't a 4L60E or 4L80E where if the trans gets hung in 2 gears it is no big deal because there are one way clutches. The ALLISON is a clutch to clutch transmission, and one bad timed shift will QUICKLY rip hard parts clean out of the trans. A PROPERLY BUILT trans set up right with a good ECM tune will have virtually no noticeable defuel on the shifts, and will live a LONG life. A fully built trans by the best in the country with a bad tune with no defuel can make for an awfully expensive door chock when it sends your trannies insides into shratnel.

[HTMtrSprt]

Word of caution to others reading this, disabling the defuel on shifts is HIGHLY NOT RECCOMENDED. And is a GOOD recipe for grenading your trans. This isn't a 4L60E or 4L80E where if the trans gets hung in 2 gears it is no big deal because there are one way clutches. The ALLISON is a clutch to clutch transmission, and one bad timed shift will QUICKLY rip hard parts clean out of the trans.
????? - ANY transmission with excessive overlap WILL destroy itself - INCLUDING 4L60E's and 4L80E's. The allison in not special.

A PROPERLY BUILT trans set up right with a good ECM tune will have virtually no noticeable defuel on the shifts, and will live a LONG life. A fully built trans by the best in the country with a bad tune with no defuel can make for an awfully expensive door chock when it sends your trannies insides into shratnel.
So..... a trans can have no "defuel" and live but if it has no "defuel" it won't live. You might want to re-think that statement.
In a diesel engine, fuel IS torque. They are directly linked. To reduce one is to reduce the other. It is a function controlled solely by the ECM and TCM working in unison or the ECM on it's own - the ECM to control max stress on the engine or as RPM/speed control. The TCM requests the ECM to "defuel" to protect the transmission's mechanical limits. Whether the trans is built or not has NOTHING to do with the fact that I have a TCM requesting a reduction in torque from the ECM during light throttle shifts despite the fact that I have removed all visible means of doing so from BOTH the ECM and TCM programming. THAT is the reason I have posted here.

[THEFERMANATOR]

????? - ANY transmission with excessive overlap WILL destroy itself - INCLUDING 4L60E's and 4L80E's. The allison in not special.

So..... a trans can have no "defuel" and live but if it has no "defuel" it won't live. You might want to re-think that statement.
In a diesel engine, fuel IS torque. They are directly linked. To reduce one is to reduce the other. It is a function controlled solely by the ECM and TCM working in unison or the ECM on it's own - the ECM to control max stress on the engine or as RPM/speed control. The TCM requests the ECM to "defuel" to protect the transmission's mechanical limits. Whether the trans is built or not has NOTHING to do with the fact that I have a TCM requesting a reduction in torque from the ECM during light throttle shifts despite the fact that I have removed all visible means of doing so from BOTH the ECM and TCM programming. THAT is the reason I have posted here.

I FULLY understand how the defuel works, and maybe you should try quoting me correctly. I said very clearly that a good tune set up properly would virtually no NOTICEABLE defuel, whereas a tune with NO defuel can destroy one QUICKLY. And 4L60E/4l80E's by design can have overlap without suffering severe consequences in many gears. When you have a trans that shifts by engaging a band, and then a one way roller clutch to safeguard when the next clutch pack comes in, it is inherent that it's design will be more forgiving. ANY direct clutch to clutch transmission does not have this forgivness factor built in. Like I said, it's your trans to do with as you please. But others have tried this and learned an EXPENSIVE lesson. And others would be wise to tread lightly into this area.

As for your question, you must be overlooking a defuel request from somewhere, or it is a table we don't have access to since we only get to see maybe 2-3% of what is actually in the TCM code. And it doesn't have to be the TCM calling for the defuel for it to pull fuel.

[Quinton]

I'm having a problem with the trans tuning also. The stock TCM tune runs fine and shifts fine. But when I go to raise the rpm shift point to 3400, it hangs/defuels. I can't figure out why it's doing it. I will post the Tcm tune and let y'all take a look. I've raised the torque limits/ d5196 table at 3400-3600 to 1000 any ideas?

[Wheelz]

Sounds like the basic engine rev limiter if I had to guess with what info I've got

[Quinton]

It doesn't bounce though like a rev limiter, it gets there just fine the hangs and then shifts. It doesn't set there for long then shifts.

[Wheelz]

It's not a hard limiter. It's a soft limiter so it slowly defuels

[Quinton]

It's not a hard limiter. It's a soft limiter so it slowly defuels

Hmm okay ill check it out ECM tuning then right?

[Wheelz]

Yup. ECM tune. And soft limiters can be set at 3200 but the way they roll fuel off will let the engine run up to 3400-3600 depending on how hard you were in it. I'm not for sure that's what it is, just I'd check that if you haven't changed the rev limiters already.

[Quinton]

Yup. ECM tune. And soft limiters can be set at 3200 but the way they roll fuel off will let the engine run up to 3400-3600 depending on how hard you were in it. I'm not for sure that's what it is, just I'd check that if you haven't changed the rev limiters already.

Alright I will double check that and report back.

[THEFERMANATOR]

Check your max torque VS RPM table in your ECm tune. it is often overlooked and will limit the fuel regardless of what you set the main tables to.

[Quinton]

Check your max torque VS RPM table in your ECm tune. it is often overlooked and will limit the fuel regardless of what you set the main tables to.

I've got it set to 950 all the way to 4000 rpm. Only thing I saw was one limiter not raised. Will try that

[GMC-2002-Dmax]

Its the way the pedal position to desired torque/torque based fuel/main injection pulse are working together.

You have to make sure that the three are happy or it will lay over.

It has zero to do with the tcm tuning.

[Quinton]

Its the way the pedal position to desired torque/torque based fuel/main injection pulse are working together.

You have to make sure that the three are happy or it will lay over.

It has zero to do with the tcm tuning.

Ya I know that's how the Lbz/lmm's work off of. Still slowly learning them. Lly/lb7 are easy.

[THEFERMANATOR]

Ya I know that's how the Lbz/lmm's work off of. Still slowly learning them. Lly/lb7 are easy.
LLY/LB7 do as you tell them to, LBZ isn't to bad, but LMM's keep you guessing. With an LMM you can write the tune to do what you want, but it always seems to take on a mind of it's own because of some obscure limiter or multiplier you overlook or don't think would apply until you log it. And a tune that works in one won't neccesarily work in another.

[vortecfcar]

In a diesel engine, fuel IS torque. They are directly linked. To reduce one is to reduce the other. It is a function controlled solely by the ECM and TCM working in unison or the ECM on it's own - the ECM to control max stress on the engine or as RPM/speed control. The TCM requests the ECM to "defuel" to protect the transmission's mechanical limits. Whether the trans is built or not has NOTHING to do with the fact that I have a TCM requesting a reduction in torque from the ECM during light throttle shifts despite the fact that I have removed all visible means of doing so from BOTH the ECM and TCM programming. THAT is the reason I have posted here.

FWIW,

From the best I can tell in the logs, there exist algorithms in both the 5 speed and 6 speed controllers that dynamically adjust the defuel based on how well the trans is meeting it's desired shift time. These algorithms become more evident as you increase torque at lower throttle inputs, presumeably because the trans doesn't have the line pressure to properly execute the shift a the higher torque load.

In the 5 speed, defuel can be axed completely via table D5197 in the TCM. People will throw rocks at if you do it, but maybe that doesn't bother you. :)

In the 6 speed, the shift defuel cannot be disabled completely with the current .calz offering. It can be lessened and made to appear more or less seamless via fuel curve tuning, but it cannot be disabled completely in the TCM (which is where the shift torque limit request originates).

Nick

[GMC-2002-Dmax]

FWIW,

From the best I can tell in the logs, there exist algorithms in both the 5 speed and 6 speed controllers that dynamically adjust the defuel based on how well the trans is meeting it's desired shift time. These algorithms become more evident as you increase torque at lower throttle inputs, presumeably because the trans doesn't have the line pressure to properly execute the shift a the higher torque load.

In the 5 speed, defuel can be axed completely via table D5197 in the TCM. People will throw rocks at if you do it, but maybe that doesn't bother you. :)

In the 6 speed, the shift defuel cannot be disabled completely with the current .calz offering. It can be lessened and made to appear more or less seamless via fuel curve tuning, but it cannot be disabled completely in the TCM (which is where the shift torque limit request originates).

Nick

Fastest way to wreck a 5 speed is shutting off the defuel request.

But you already knew that.

:music_whistling_1:

[killerbee]

One of MANY many threads...Prefer not to let this one die. We have all been waiting for defuel adjustment in the A40 for 5 years. A pretty serious omission where tuning effectiveness is concerned. Will this problem get some acknowledgment before the A50/LML project?

[GMC-2002-Dmax]

I have not had any issues with tuning the ecm properly to limit the defuel to an acceptable level, in fact I can get it so that it pulls only a small amount of fuel on the shift all thru ecm tuning only

[killerbee]

Yes, of course you can. :)

[GMC-2002-Dmax]

Yes, of course you can. :)

All the duramax models have to have properly written ecm tuning because if they are not written correctly they will defuel too much or not enough.

The LBZ and LMM use a different method to achieve the same results as the 2001-2004.5 models.

It will take some creativity and dedication to figure it all out, there is a way to do it.

[Dmaxink]

11.80...stock air/fuel no drugs, 5600lbs...

Guess what tcm tune? ...Stock
Guess what defuel values? ...Stock

From the factory they shift great... So go one table at a time and when you finally mod a certain table that throws your tcm out of whack, return that table to stock.. Start over.. And write down what does and doesn't work.

At the end of the day you end up with tons of knowledge and a well tuned truck.

Kory

[vortecfcar]

You wouldn't be saying that if sled pulling an LMM was your sport of choice. There is a utility for this update, even though may not improve dragstrip numbers. :)

[GMC-2002-Dmax]

I have a lot of LMM sled pullers, nobody has brought anything to my attention that is inhibiting them in any way.

Just an FYI.

But what do I know ?

[hog]

In sled pulling, there are guys shifting during a pull? I thought it was a "lock'er" in 3rd gear sort of deal. Having the trans shifting during a pull would be horrible, esp. with any sort of defuel. I would think that would casue a serious loss of pulling momentum.

peace
Hog

[vortecfcar]

In sled pulling, there are guys shifting during a pull? I thought it was a "lock'er" in 3rd gear sort of deal. Having the trans shifting during a pull would be horrible, esp. with any sort of defuel. I would think that would casue a serious loss of pulling momentum.

peace
Hog

That's right Hog. At this point it's a lock in one gear and go sort of deal. The downside here is that if you have power enough to go to 4th, you need to start in 4th to avoid the defueled WOT 3-4 shift.

Nick

[Dmaxink]

You wouldn't be saying that if sled pulling an LMM was your sport of choice. There is a utility for this update, even though may not improve dragstrip numbers. :)

Espo runs his LMM at 5k rpm, 475 single, 29k rail and starts in 3rd with no issues from messing with shift time and torque table modded... Heck, my A50 doesn't hold my LML back even at 4400 with a stock TCM... When I bump shifts to 4k for testing it had no issues either. I just never had any need to modify the torque tables in the TCM. Obviously, if I had one defuel one me hard I would... But out of the many many I have done I have had no need to.

Our LMM slams 140+mph runs no problem with big rpm... Not a puller, but same diff... Rpm and load.

Not saying it totally isn't necessary, but I have not come across one that needed any, and like you... Have done quite a few.

What does the tcm defuel it to for those of you that have had the need to modify the tables.

[vortecfcar]

Espo runs his LMM at 5k rpm, 475 single, 29k rail and starts in 3rd with no issues from messing with shift time and torque table modded... Heck, my A50 doesn't hold my LML back even at 4400 with a stock TCM... When I bump shifts to 4k for testing it had no issues either. I just never had any need to modify the torque tables in the TCM. Obviously, if I had one defuel one me hard I would... But out of the many many I have done I have had no need to.

Our LMM slams 140+mph runs no problem with big rpm... Not a puller, but same diff... Rpm and load.

Not saying it totally isn't necessary, but I have not come across one that needed any, and like you... Have done quite a few.

What does the tcm defuel it to for those of you that have had the need to modify the tables.

I'm sorry Kory, I had trouble deciphering exactly what you mean. Are you're saying you've tuned an LMM Sled puller that shifts WOT 2-3 or 3-4 near 4000RPM and have not experienced the defuel from hell? Or are you simply saying that you've never had to modify torque tables in a high range application?

The defuel logs in Normal/TH/drag race vs. 4Low do not show the 'same diff' in my experience.

Nick

[Dmaxink]

I'm sorry, I had trouble deciphering exactly what you mean. Are you're saying you've tuned an LMM Sled puller that shifts WOT 2-3 or 3-4 near 4000RPM and have not experienced the defuel from hell? Or are you simply saying that you've never had to modify torque tables in a drag racing application?

The defuel logs in Normal/TH/drag race vs. 4Low do not show the 'same diff' in my experience.

Nick

Yes, Espo of Suncoast actually launches in 3rd, shifts 3>4 at 4k rpm and we have not run into the defuel issue.... I was saying as well in my A50 experience it appears to be the same way.

I'm sure now that I said that I will have the issue pop up my luck!

Kory

[vortecfcar]

Both of these trucks are in 4 wheel Low with a sled behind them?

[LB72004]

after all of this great information, has anyone determined the "safe" defuel amount so the transmission will survive and shift great?

example:

so a stock tune running x mm3 of fuel performs a shift and ECM goes into defuel and injects the new amount of mm3s. this has been determined to be x mm3 lower or x % less and is obviously safe being a stock tune.

now this truck gets a higher HP tune, and now is able to push x number more mm3s at the same RPM, so what would the new safe level of mm3s be for this tune during defuel shifts? is it still the same number of mm3s as the stock tune? i think not. is it a certain % less, not likely that simple.

i would think it lies somewhere between transmission life multiplied by quality shifts divided by the HP, or some such nonsense.

High HP, Long Transmission Life, No Defueling; pick any two

Allison and Duramax tuning gurus please shed some light on this

Thanks Jason

[Wheelz]

Just for comparison, in my tunes I use torque reduction to limit torque output to (ex) 200 ft-lbs during the shift. Less output than that I have no reduction. Just throwing that out there

[LB72004]

Wheelz,

are you saying that with less then 200 ft-lbs of commanded torque you dont have any defuel? i have contemplated doing the same thing on mine thinking that it should be fine with low throttle/torque for better shift feel.

[Wheelz]

Yep. In my head it makes sense that you defuel to protect from excessive torque and to accelerate the shift. Under low power the tranny will shift fine without defueling. But you still de-fuel under high load to protect it during high power shifts.

[LB72004]

thanks, i will give this a shot and see how it feels

[Wheelz]

I make no promises, but you may have to experiment with the value to defuel to.

[LB72004]

after looking over my LB7 tune, this looks to be a lot harder then i originally thought. seems that the tunes are not set up to be able to do this. looks like i would have to do a lot of logging and tweaking till i got a mm3 number that matched the throttle based injection quantity while also shifting/defueling

right now the mm3s in the torque limited injection quantity equals the throttle base in injection quantity and it still defuels. i believe the transmission requests a defuel percent and the ECM looks at the torque limited injection quantity table and subtracts the percent from it. the problem is not knowing what percent the transmission will ask for.

seems like this would be easier i the later years but not the LB7 and LLY

any thoughts?

[GMC-2002-Dmax]

Shift quality is the hardest thing to dial in on the earlier years, it takes a long time to get it perfect at all TPS%/RPMS.

You are correct, its not easy

[LB72004]

true, true..

my shift quality is not bad by any means, it is actually quite good. i currently use a excel spreadsheet to dial it in and it seams to work the first time. i have not run yet with any defuel so i was wondering if it would be any better and the low torque areas would be the way to test it, but it is not that easy