View Single Post
  #19  
Old 08-13-2017, 09:36 AM
upallnight's Avatar
upallnight upallnight is offline
Member
 
Join Date: Aug 2012
Location: Cook County
Posts: 7,280
upallnight is on a distinguished road
For the ZF5HP24, electronically controlled overlap gearshifts are used on all shifts except First to Second. First is the only gear with a freewheel clutch, since at the low speeds the first to second change occurs, the accuracy of the data from the input/output speed sensors is limited. All the shifts are completely closed loop controlled so that a consistently high shift quality can be guaranteed through the service life and production tolerances. Conventional 4-speed transmissions use just two solenoid valves (on or off valves) for gear selection, with the old clutch pack being disengaged before the new clutch is engaged. A simple truth table of the solenoid valves state would immediately indicate the gear selected. This transmission uses five pressure regulators and three solenoid valves and a simple truth table would not indicate which gear is selected. This is because the pressure regulators are not simply “on or off’, but allow the pressure to the clutch packs to be balanced to give the appropriate gear. Overlap shifts mean that neutral is not selected between gears. Pressure is applied to the “next gear” clutches as pressure is reduced on the “old gear” clutch packs. This requires a high TCM processor overhead as the two clutch pressures must be balanced throughout the gearshift to give a high shift quality and protect the transmission from damage. The advantage of this system is that drive is not interrupted, torque is always applied to the wheels throughout the gearshift and greater shift quality is possible. Since there is no neutral between gears, the gearshifts are no longer hydraulically protected. Hence, the TCM monitors the change characteristic for anomalies. If the shift does not match the specified characteristic (rate of change of input and output speeds etc.) then the gearshift is aborted to prevent transmission damage.

Overlap shifting is only possible using a high speed communications link to the engine management system so that shift energy management can be closed loop controlled in real time. Shift energy management allows the transmission to control the engine output torque during a gear shift, so that excess power is not dissipated in the transmission friction elements during the shift. The functions of shift energy management are: 1. Increasing the transmission life by shortening the slipping time. 2. Improving the shift comfort by reducing the step change in torque caused by the gearshift. 3. Limiting the maximum engine power transferred into the transmission.

The slam shift issue is due to a pressure issue within the trans. This could be from a scored piston valve in the valve body, broken o-rings or a drum that has cracked and is not allowing the clutch pack to maintain pressure.
__________________
2006 Infiniti G35
2001 BMW 3.0I E53 X5 Build date 08/2000 SOLD
Lotus Europa 1970 Destroyed by fire
Lotus Europa 1970 S2 Renault Powered
Lotus Type 52 1970 Twincam Webers Powered
PORSCHE 911 Targa 1982 The Garage Queen
Audi Avant donated to Kars for Kids
BMW 525IT Sold
Audi 4000CS Quattro Sold
Jensen Healey Lotus Powered Sold
Opel 1900 Sold
Triumph Spitfire 1971 Sold
Triumph Spitfire 1968 Sold
Plymouth "Cuda" 340 Six pack SOLD
Reply With Quote

Sponsored Links