Lots of talk right now about trans shifting and what not. but I can't find what I'm looking for.

Right now if I really haul on my truck when it goes to shift it seems like i revs up inbetween shifts. Sometimes it does it pretty bad, sometimes not so bad. If I clear the taps, for a while afterwards it shifts pretty nice but slowly goes back to like it is usually.

Anybody else got something like this going on? Whats the thoughts on this? I havent even opened up the tranny tune on the truck and I didnt really plan on messing with it but if I can make it better than I'll do it.

Also, sometimes the truck will just hang out around 3000rpm for a bit longer than I would like before it shifts, and then when it does it usually shifts to the next gear and immediately locks the torque converter. Almost drops the RPM's too much. I suppose some of this is due to having the 35" tires on it too. Anyone got opinions on this too?

Do some logging and observe mm3 while shifting. Sounds like B0744 needs some tweaking.

Do some logging and observe mm3 while shifting. Sounds like B0744 needs some tweaking.
I agree with RaceHemi. That is where I would start if it were my tune.

i was playing with this, and those values are the mm3 that it takes away from the main correct?

They do not add or subtract from the main. They become the max main for a specified torque requirement.

Ok.

For mm3 I would just log the main injection rate?

And I see it might be handy to log GM.DMAX_trq_dma.... just to see what kind of torque value I'm getting right before it shifts, or as it shifts.

And if I'm pondering this correctly, it will be a certain rpm and torque level when it goes to shift, and the mm3 value that it gives will be the limit on what it can inject during the shift?

Just out of curiosity though... is this table only active when the TCM triggers the ECM to limit torque because a shift is occurring?

Right now I basically have no limit, between 2800-3200rpm I'd be anywhere between 96mm3 and 126mm3. And if I recall correctly since only 100mm3 can be commanded, anything over that value reverts to 100.

What kind of numbers should I be looking at to get it where I want it? I imagine that it will be different for different tunes due to the difference in power levels and other stuff. Would it be logical to cut it back bit by bit until what I have going on starts to diminish to a reasonable level? Or is their more science to this particular table?

I see now how my amatuer tuning is falling by the wayside. I gotta say though that I'm impressed with myself for coming this far.

Log data. Use the GM.FUELQ_MAIN_DMA pid for fuel volume. Watch the areas in the GM.DMAX_TRQ_DMA to study the torque commaned from the ECM and how it limits it during a shift. You can also study the fuel volume and see where you need to adjust it during a problem shift. You can link the scan data to the tuning tool and the runway highlighter will show you what part of the tables are being used which will help pinpoint where to adjust.

Studying logged data is a great tool in starting to understand how things work.

I was in your shoes 2 years ago.

it doesn't help any that GM over complicates their software....

it doesn't help any that GM over complicates their software....

no kidding. :eek: and how a .5mm change can really effect things.

just their map layout, and multipliers, and everything else is unreal.... there are much simpler ways to do this.

i made a tune last week and adjusted some lower mm3 fueling mainly 30mm3 and higher smoothed it down to 20mm3. i wanted to see how it worked to get some more low end grunt. well it worked but it seems that that was a result of the extra fueling. just around town driving though, 25-30% throttle. over that it shifts fine. firm, crisp, and with the tcm tune with no defuel. just dowm low it seems like an over fuel during the shifts making it sloppy, and soft. i will try logging those pids and see how it works. once i get back to work.

gotta be careful, if you don't defuel you will slip the clutches as well and can burn them up faster.