Thread: ZF 4HP22 problems and valve block rebuild link

The solenoid harness is STC4782

I checked the transmission end of the harness and it didn't look too bad from the outside. There were no pools of trans fluid or obvious leaks, but the wires coming out the back of plug were damp with oil.

This is the "diagnostic phone video":
[ame=http://www.youtube.com/watch?v=8iKlf7k9X2k]4HP22 harness plug - YouTube[/ame]

When I disconnected the plug the contacts were soaked in trans fluid, so I've given both sides a clean with isopropyl alcohol and reconnected until I get a chance to replace the harness.

Cleaning out the connectors at both ends of the harness has made an obvious difference to the shift quality, and the box is behaving much better on the 1-2 upshift.

The connector clean is a bit of a temporary fix, so I'm still looking at doing the solenoid harness next week.

cheers
Paul

thanks for your comments on the nanocom problem, ive posted it on their support forum to try get it fixed. (and here High/Low Range - Crossed wires or Nanocom?)

Im posting my progress with my full rebuilt here:
ZF4HP22 do it yourself overhaul


Ive been trying to find out how the ecu would even know the modulation pressure as there is no pressure sensors that im aware of, and ive torn down my box/body completely, just 4 solenoids and a speed sensor...

Originally Posted by haydent

Ive been trying to find out how the ecu would even know the modulation pressure as there is no pressure sensors that im aware of, and ive torn down my box/body completely, just 4 solenoids and a speed sensor...

It's explained in the WSM, the ECU's calculations are based on mapped values against TPS and RPM inputs not on a sensor input:

Shift control
To provide the different driving characteristics for each mode of operation, the EAT ECU incorporates different shift
maps of throttle position/engine speed. Base shift points are derived from the appropriate shift map. When a shift is
required, the EAT ECU sends a request to the ECM for a reduction in engine torque, in order to produce a smoother
shift. The percentage of torque reduction requested varies according to the operating conditions at the time of the
request. When the EAT ECU receives confirmation of the torque reduction from the ECM, it then signals the shift
solenoid valves in the gearbox to produce the shift. To further improve shift quality, the EAT ECU also signals the
pressure regulating solenoid valve to modulate the hydraulic pressure and so control the rate of engagement and
disengagement of the brake clutches

With time, the components in a gearbox wear and the duration of the gear shifts tends to increase, which has an
adverse effect on the brake clutches. To counteract this, the EAT ECU applies a pressure adaptation to each shift.
To calculate the adaptations, the EAT ECU monitors the pressure modulation used, and time taken, for each shift. If
a subsequent shift of the same type, in terms of throttle position and engine speed, has a longer duration, the EAT
ECU stores an adaptation for that type of shift in a volatile memory. The adaptation is then included in future pressure
calculations for that type of shift, to restore shift duration to the nominal.

Thanks, I figured this was the only option. So its an assumed pressure and would be reliant on a theoretical factory calibrated and operating transmission, and as such would not be able to indicate poor performance of any part such as hydraulic pump, valve body or filter for example.

Similarly (and how I got onto this topic) could not be used to calibrate the modulation valve adjuster on the valve block, which is controlled by the pressure solenoid.

What/where is WSM ?