TCM Adaptation - 8HP45/845RE

The 8HP45/845RE transmission will perform clutch adaptations over the life of the vehicle to account for the normal build variation of the transmission hardware when new, and allow for the normal wear of the clutch friction material over the life of the transmission. The TCM continuously self calibrates and learns shift points and clutch apply times. It is necessary to perform clutch adaptations to provide the proper baseline transmission adaptation. The adaptation procedure should be performed if any of the following procedures are performed:

• Transmission Assembly Replacement.
• Transmission Control Module Assembly (TCMA) Replacement.
• Internal Transmission repairs.
• Torque Converter Replacement.
• If Transmission Adaptations were cleared.

1. With the scan tool, clear any DTCs that may be set.
2. Drive the vehicle until the vehicle temperature is greater than 30° C (86° F) for Fast Filling Adaptation or 50° C (122° F) for Standard Clutch Filling Adaptation.
3. Perform the Clutch Adaptations using the information below.

Reading Clutch Adaptations 

For the 5 Clutch Packs (A, B, C, D, & E) each will have 4 data sets to read in the scan tool under the TCM section. Using Clutch A as an example, the data labels are:

• Clutch A- Filling Pressure:  This indicates the amount of pressure in milli-bar (mbar) (PSI) the transmission is adding or removing to adapt to the normal new build variation or normal clutch wear over the life of the transmission.
• Clutch A- Fast Filling Counter:  This is the number of Clutch Filling Pressure adaptations that have been performed. It is called fast filling, since these adaptations are the first quick learned values on a new transmission or after clutch adaptations are cleared.
• Clutch A- Filling Time:  This indicates the amount of time in milliseconds (ms) the transmission is adjusting the clutch fill time to adapt to the normal new build variation or normal clutch wear over the life of the transmission.
• Clutch A- Filling Counter:  This is the number of Clutch Filling Time adaptations that have been performed.

Performing Driving Clutch Adaptations 

Drive Adaptations should be performed for a customer that has a shift quality issue since the shift quality concern may only be the effect of a new non-adapted transmission, or a transmission that may not have performed enough adaptations due to driving style. A more aggressive driving style or a driving pattern that includes a lot of highway driving in 8th gear will take longer than normal for the transmission to adapt. Adaptations are more likely to occur in lower throttle city driving.

Use the table below to identify what clutches may be involved in the shift being diagnosed.

Standard Clutch Filling Adaptation - Transmission in a Shifting State 

The first Fill Pressure adaptations occur the quickest under the following parameters in the tables below. Use the scan tool to look up Transmission Temperature, Torque and Speed numbers. Another alternative is the instrument cluster menus for transmission temperature, and the tachometer for engine speed which is the same as input speed in lockup conditions. The ideal would be to achieve the adaptations on the Fast Filling Counter after the driving adaptations. Use the smoothest roads possible, since the transmission will not adapt if it senses rough road conditions. Also use roads with minimal traffic since many of these conditions occur at relatively low vehicle speeds.

Fast Filling Adaptation - Transmission Steady State, Not Shifting 

The first Filling Time adaptations and any Filling Pressure Adaptation after the Fast Adaptations use the following procedure highlighted in the tables below. These Adaptations are done steady state in a particular gear as opposed to during a shift. It is recommended to use the paddle shifters or Gear +/- buttons on the steering wheel to hold a particular gear while trying to adapt a particular clutch.

Use the scan tool to look up Transmission Temperature, Torque and Speed numbers. Another alternative is the instrument cluster menus for transmission temperature, and the tachometer for engine speed which is the same as input speed in lockup conditions

The ideal would be to achieve at least 10-12 on the Filling Counter and Fast Filling Counter after the driving adaptations. Use the smoothest roads possible, since the transmission will not adapt if it senses rough road conditions. Also suggest using roads with minimal traffic since many of these conditions occur at relatively low vehicle speeds.