Fresh 4l80 rebuild VIOLENT to reverse

[ChrisJamesN/T]

Howdy - so I have a 03 0411 ecu running a 5.3 and a 4l80. Ecu originally 4l60. Old 4l80 went from park drive and from any gear to reverse fine. Fresh rebuild with a higher pressure valve body is violently slamming into R from P and from p to D or 3. On the Hp tuning software my ecu won?t let me adjust idle line pressure and I cannot increase the current value to bring line pressure down. Well up over 90 on the physical gauge at idle fmc 76 a
am I missing something in the software or is it my ecu won?t support a change. Tanks for your time

[kingtal0n]

At idle, going to reverse, the current should be high maybe 800mA or something. The current should only go low when you press the throttle, then it might drop the current rapidly.

Most of the time when 4l80e jam harsh into reverse its because somebody removed the reverse checkball from the valve body. This is a common mod and I feel that is a mistake. Ask rebuilder if they removed that checkball.

Is this a trans-go shift kit 4l80e, or a dual feed direct drum 4l80e?

Another possibility is the boost valve or pressure regulator valve has been upgraded but I'm not sure even that would cause such a harsh engagement, many 1000rwhp builds still using OEM PR and Boost valves.

IS there a lube to line modification done or LUBE style Pressure regulator valve installed? If lube to line was drilled into the pump, find out what diameter the hole is.
Are you using a pressure gauge on the side of the transmission to find actual pressure? Line pressure in reverse can be 300PSI at WOT for example. You can't go by the pressure displayed in HPtuners it isn't a direct comparison.