This to me sounds like the best advice around, but...
How does one know / judge what the pressures ought to be? The required pressure at any given time must at least depend on...
- which each "gear" the trans is in (as there may be different clutches / bands / servos involved in each gear)
- composition of the friction materials,
- the engine's applied torque, and
- the torque converter's torque multiplication, and
- maybe other stuff.
"What's the proper pressure" is something I've wondered about for years.
Do tell.
I like to monitor slip rpm especially on the 4L80E where the input speed sensor is physically reading it as well as commanded vs actual shift times to help sort that out.
That being said the GM torque tables are calibrated well in excess of the torque ouput the engine can deliver. GM engineers validated those pressure torque maps. I generally do not have to mess with them much to get a nice shift. If I want it to shift a little firmer, I use the Tow/Haul mapping or the mapping from a more powerful engine using the same transmission. My Express has the Tow/Haul line pressure mapping from an 8.1L for example. At higher torque output values I will decrease the desired shift time a bit and I also increase the torque cut. What that does is cuts more torque, but for a shorter period of time, allowing for a quicker shift without abusing the friction surfaces or geartrain. Would you rather cut 25% of the torque for 0.5s or 40% for 0.25-0.3s? I can tell you from having tested it, 40% for shorter time makes the shift firmer, is easier on the transmission and results in quicker acceleration. When you cut the input torque during the shift, it allows all the internal rotating parts of the transmission to change speeds more easily and quickly. Anybody that wants to reduce or remove torque management is doing it wrong, same as commanding 0 for shift times.
While it was not a setup I would have done personally, I have tuned a 4L65E that is still living behind an 8.1L in a H2. I have learned a lot about keeping those piles of garbage in one piece behind decent power. It almost all focuses on properly using torque management. The 8.1L in that application is so detuned from tq management it will not go WOT until it is at 4,000 rpm but that being said it still has far better torque output everywhere than the 6.0L it replaced, so that big heavy H2 is still alot quicker and the 8.1L moves it much more easily off road.
