Why does the 01 OS have so much better shift quality, escpecially at really low throttle. I just switched back to my original 05tcm os in my LLY and SCIII and it loves to clunk and shift hard at really low throttle it also likes to clunk on the downshifts where the 01 would not. When completely off the throttle or barley on it is when the shifting is the hardest.
01 TCM OS shifts
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GMC_2002_Dmax
The Still Master
From what I know the 01 is the closest to a standalone TCM that there ever was for these trucks. Meaning that the 01 OS uses next to nothing from the ECM to make a shift decision. Where I believe all of the latter OS's rely on more info from the ECM before making a shift. That's what I always was led to believe. Maybe tony can chime in more.
i loaded an 01 os in mine. didnt notice much of a difference if any at all....
the only weird thing it does now is under heavy braking it downshits itself like tow/haul but in normal mode
would like to know all the reasoning behind all this 01 stuff though
the only weird thing it does now is under heavy braking it downshits itself like tow/haul but in normal mode
would like to know all the reasoning behind all this 01 stuff though
The '01 system is not as sensative to adapts as the later systems. As far as a stand alone , it is not even close. They all use feedback from speed sensors and many other things for shift commands.
From what I have learned the 01 is pretty stupid and very painfully slow to learn and adapt, and the 3-4 shift is ROUGH most of the time. My 02 OS shifts like a cadilac on the upshifts and clicks off the gears faster under WOT, but it will click or clunk on the 3-2 and sometimes the 4-3 and the 2-1 can be rough as well. The 03 OS shifted pretty nicely and smoothly all around and adapts quickly, but in my app I can't lock out OD so it doesn't fit the bill for me.
x2 Ferm, I'm running 02 with the OS #15172881, an I made few minor tweaks to the torque limit table, an it shifts very sweet, I don't think my tranny could shift any better, that' my opinion, :thumb:
This is exactly what im talking about with the 01os. I dont really remember how it was before I got my scIII. I guess there is no one good os its all a compromise.
If it wasn't for the 3-4 shift in the 01, I would run it all the time. For some reason though mine will shift hard on the 3-4 shift if you let it sit for more than 5 minutes with the 01, the 02 OS does it slightly but nothing like the 01 does. The trade off is that the 3-2 in the 02 OS will click or clunk sometimes with my idle set at 680(stock 02+), but if I lower it down to 600 like I have in my 01(which is the idle I prefer) it will clunk and sometimes bang on the downshifts with the 02. I wish there was some way to take the best of each one and merge it together.
You know I drive my dad's 03 and love how smooth that things shifts all the time. After putting the 01 OS in mine they are almost as smooth, plus my 3-4 WOT shifts are way smoother.
It is in the DP tune library under stock allison tunes. Says most recent calibration. It was placed there by Flashscan, i believe he works R&D for EFI Live. They'd be the ones to know i guess. Anyways, the tune works well for me. :thumb: