600 rpm slip limit

[DURAtotheMAX]

I am only interested in knowing definatively if the slip limit is software linked.

After talking with a couple people in Allison software, the threshold is somewhere around 650rpm. If turbine vs. input speed (converter slip) is over ~650rpm, there is some all-overriding table in the software that says "F you" and prohibits converter lockup until slip drops below there.

So we know for a fact it exists, its just that EFILive has not found it/mapped it out. I doubt they are going to re-visit Allison stuff again, which is why I went ahead and designed/build the Allison lockup controllers; to override the TCM and force lockup to happen, even if the software is inhibiting it.


The other big table that I wish EFILive had for the 5-speeds was the table that forces converter unlock for a second during a WOT downshift/kickdown. And whats strange is 04-05 LLY TCM OS's DO NOT unlock the converter during a WOT downshift. So when you're cruising on the highway in 5th, and stomp on it to pass someone, the trans does a 5-4 downshift and keeps the converter locked all the way through it. (which is good)

On the 01-03 TCM OS's, the converter unlocks, trans does the downshift, and then the TCM [is supposed to] relocks the converter once the shift is complete. THE PROBLEM WITH THAT is that once you unlock the converter and downshift at WOT under big power, the converter slip RPM immediately zings above 650rpm and you get into "limbo" there where the converter lockup is inhibited again. So when you're on the highway, you stomp on it, downshift/unlock, and the truck just sits there SCREAMING away in 4th gear and you dont actually accelerate at all (because the converter isnt locked)...then 5 seconds later, converter "catches up", TCM relocks it, THEN you start accelerating, then it shifts back into 5th gear. Its freaking obnoxious, and dare I say dangerous, because you go to pass someone, and the truck just makes a lot of noise, but you cant actually pass the person because the stupid TCM unlocks the TC and then just sits there saying "F you" and wont relock (thus not allowing the truck to actually accelerate and shift back into 5th).

And, go figure, the 2004-2005 TCM OS is the one that shifts like crap under big power, and the 2001-2002 TCM OS's work perfectly under big power. So you cant have your cake and eat it. You either have a TCM that lets you do WOT kickdown's/downshifts and actually pass people right away, but shifts like crap otherwise.......or you have a TCM that shifts awesome/predictably, but effectively doesnt allow you to ever do any WOT downshift/passing.

Ben

[Dmaxink]

Thanks for sharing Ben, always appreciated! Nice info.

[THEFERMANATOR]

After talking with a couple people in Allison software, the threshold is somewhere around 650rpm. If turbine vs. input speed (converter slip) is over ~650rpm, there is some all-overriding table in the software that says "F you" and prohibits converter lockup until slip drops below there.

So we know for a fact it exists, its just that EFILive has not found it/mapped it out. I doubt they are going to re-visit Allison stuff again, which is why I went ahead and designed/build the Allison lockup controllers; to override the TCM and force lockup to happen, even if the software is inhibiting it.


The other big table that I wish EFILive had for the 5-speeds was the table that forces converter unlock for a second during a WOT downshift/kickdown. And whats strange is 04-05 LLY TCM OS's DO NOT unlock the converter during a WOT downshift. So when you're cruising on the highway in 5th, and stomp on it to pass someone, the trans does a 5-4 downshift and keeps the converter locked all the way through it. (which is good)

On the 01-03 TCM OS's, the converter unlocks, trans does the downshift, and then the TCM [is supposed to] relocks the converter once the shift is complete. THE PROBLEM WITH THAT is that once you unlock the converter and downshift at WOT under big power, the converter slip RPM immediately zings above 650rpm and you get into "limbo" there where the converter lockup is inhibited again. So when you're on the highway, you stomp on it, downshift/unlock, and the truck just sits there SCREAMING away in 4th gear and you dont actually accelerate at all (because the converter isnt locked)...then 5 seconds later, converter "catches up", TCM relocks it, THEN you start accelerating, then it shifts back into 5th gear. Its freaking obnoxious, and dare I say dangerous, because you go to pass someone, and the truck just makes a lot of noise, but you cant actually pass the person because the stupid TCM unlocks the TC and then just sits there saying "F you" and wont relock (thus not allowing the truck to actually accelerate and shift back into 5th).

And, go figure, the 2004-2005 TCM OS is the one that shifts like crap under big power, and the 2001-2002 TCM OS's work perfectly under big power. So you cant have your cake and eat it. You either have a TCM that lets you do WOT kickdown's/downshifts and actually pass people right away, but shifts like crap otherwise.......or you have a TCM that shifts awesome/predictably, but effectively doesnt allow you to ever do any WOT downshift/passing.

Ben

You oughta ride in mine. I run the 01 OS, but since it only gets minimal inputs and I have lowered shift points for my 3:42 gears it does some wierd crap sometimes. If I cruise for extended periods at 30-35 it will lock the converter in while in normal mode so long as trans temps stay in the 180-200 range, and it will lug it down when it does it. Other times it will unlock on a WOT downshift and then the next time it won't. I've ridden in trucks with the same OS and they are very predictable, but mine is anything but. And I won't even go into grade braking and it's tendancy to not ever work with the 01 OS, but other times it will engage while on flat land in normal mode just cruising. It would be nice to be able to see somem ore of what is inside the TCM though.

[THEFERMANATOR]

Would be REALLY nice if you guys could take a look at this slip limit for us again. Went to the track last night and it is really disapointing to go slower at WOT than 80% throttle because the converter wouldn't lock. And I'm not anywhere near the 600 RPM slip limit with mine either, maybe 400 or so and it wouldn't lock up.

[Dmaxink]

We will be doing extensive testing this week