NHTSA ID Number: 10138017
Manufacturer Communication Number: 14-07-30-001G
Summary
This informational bulletin explains how to diagnosis and perform a transmission fast learn procedure to fix a harsh shift at low speeds. Shifts that feel too firm (harsh), slips or flares.
1 Affected Product
Vehicle
Low mileage vehicles equipped with the 8L90 automatic transmission with shifts that feel too firm (harsh), slips or flares.
Customers should be advised that the transmission makes use of an adaptive function that will help to refine the shift feel and improve shift quality while driving.
Clearing the shift adapts without performing a Service Fast Learn should not be considered a repair procedure as the transmission will simply relearn the previous settings.
Correction
The following should be used to determine what steps should be followed within this document. The 8-Speed transmission utilizes a total of 5 clutches to obtain all the ratios. Utilize the chart within this document to determine which clutch may require additional adaptive learning.
- If a transmission assembly, valve body, torque converter, TCM, or any repair regarding shift quality was required, reset the adapts using Service Fast Learn. Evaluate the shifts and further learn pressures and volumes if required.
- If a customer has a specific shift concern, the Service Fast Learn should be skipped. Complete the driving learn procedure to further learn pressures and volumes for the complaint shift.
Transmission Adaptive Functions
The Hydra-Matic 8-Speed RWD transmission utilizes a line pressure control system during upshifts to compensate for new transmission build variation as well as the normal wear of transmission components. The variation experience on a new and normal wear of the apply components within the transmission over time can cause shift time (the time required to apply a clutch) to be longer or shorter than desired.
In order to compensate for these changes, the transmission control module (TCM) adjusts the pressure commands to the various pressure control (PC) solenoids to maintain the originally calibrated shift timing. The automatic adjusting process is referred to as “adaptive learning” and it is used to ensure consistent shift feel plus increase transmission durability.
The TCM monitors the A/T input speed sensor (ISS) and the A/T output speed sensor (OSS) during commanded shifts to determine if a shift is occurring too fast (harsh) or too slow (soft) and adjusts the corresponding PC solenoid signal to maintain the set shift feel. The purpose of the adapt function is to automatically compensate the shift quality for the various vehicle shift control systems. The adapt function is a continuous process that will help to maintain optimal shift quality throughout the life of the vehicle.
How to Adapt Your Transmission
Transmission adapts can be reset and relearned on most vehicles through GDS 2 by using the Transmission Service Fast Learn procedure. This procedure is completed in the service stall and no vehicle driving is required.
To complete the Transmission Service Fast Learn procedure, enter GDS 2 Diagnosis and navigate to:
– Module diagnostics
– Transmission Control Module
– Configuration / Reset Function
– Transmission Service Fast Learn
Transmission Service Fast Learn is the recommended method to reset and relearn the adapts. This procedure is available on all trucks and SUVs and on Corvettes built on September 29, 2014 and later. For Corvettes built before September 29, 2014 the Transmission Service Fast Learn will be available if the TCM calibration is updated to the latest available on TISWeb.
When the Service Fast Learn is complete, perform a test drive and note any soft or harsh shifts.
1 Associated Document
Manufacturer Communications
Bulletin No.: 14-07-30-001G
Date: Mar-2017
https://www.nhtsa.gov/recalls?nhtsaId=10138017
MC-10138017-9999.pdf 116.252KB
NHTSA ID Number: 10112777
Manufacturer Communication Number: 14-07-30-001F
Summary
This informational bulletin provides information on transmission adaptive functions and correcting low mileage harsh shifts by completing a transmission service fast learn
1 Associated Document
Manufacturer Communications
Bulletin No.: 14-07-30-001F
Date: Mar-2016
https://www.nhtsa.gov/recalls?nhtsaId=10112777
MC-10112777-9999.pdf 115.649KB
NHTSA ID Number: 10113638
Manufacturer Communication Number: 14-07-30-001D
Summary
This informational bulletin provides technicians with information on transmission adaptive functions and correcting low mileage harsh shifts.
1 Associated Document
Manufacturer Communications
Bulletin No.: 14-07-30-001D
Date: May-2015
https://www.nhtsa.gov/recalls?nhtsaId=10113638
NHTSA ID Number: 10139441
Manufacturer Communication Number: 14-07-30-001C
Summary
This informational bulletin provides information on transmission adaptive functions when correcting a customer concern that shift feels to be too firm (harsh) or may slip or flare.
1 Associated Document
Manufacturer Communications
Bulletin No.: 14-07-30-001C
Date: Jan-2015
https://www.nhtsa.gov/recalls?nhtsaId=10139441
NHTSA ID Number: 10126223
Manufacturer Communication Number: 140730001B
Summary
This information bulletin provides a procedure for the technicians to perform a transmission re-learn to correct a customer concern of low mileage harsh shifting.
1 Associated Document
Manufacturer Communications
Bulletin No.: 14-07-30-001B
Date: December, 2014
https://www.nhtsa.gov/recalls?nhtsaId=10126223
NHTSA ID Number: 10066092
Manufacturer Communication Number: 14-07-30-001B
Summary
SUMMARY TO BE PROVIDED ON A FUTURE DATE.
1 Associated Document
Service Bulletin Document
Bulletin No.: 14-07-30-001B
Date: December, 2014
https://www.nhtsa.gov/recalls?nhtsaId=10066092
NHTSA ID Number: 10114286
Manufacturer Communication Number: 14-07-30-001A
Summary
This information bulletin provides a procedure for the technicians to perform a transmission re-learn to correct a customer concern of low mileage harsh shifting.
1 Associated Document
Manufacturer Communications
Bulletin No.: 14-07-30-001A
Date: October, 2014
https://www.nhtsa.gov/recalls?nhtsaId=10114286
MC-10114286-9999.pdf 245.536KB
NHTSA ID Number: 10095172
Manufacturer Communication Number: 14-07-30-001
Summary
THIS INFORMATION BULLETIN PROVIDES A PROCEDURE FOR THE TECHNICIANS TO PERFORM A TRANSMISSION RE-LEARN TO CORRECT A CUSTOMER CONCERN OF LOW MILAGE HARSH SHIFTING.
https://www.nhtsa.gov/recalls?nhtsaId=10095172
NHTSA ID Number: 10066091
Manufacturer Communication Number: 14-07-30-001
Summary
SUMMARY TO BE PROVIDED ON A FUTURE DATE.
1 Associated Document
Service Bulletin Document
Bulletin No.: 14-07-30-001
Date: September, 2014
https://www.nhtsa.gov/recalls?nhtsaId=10066091
SB-10066091-9133.pdf 489.744KB
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- Improved performance over previous DEXRON fluids in: friction durability, viscosity stability, aeration and foam control, and oxidation resistance
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- Backward compatible with previous Dexron automatic transmission fluids and can be used as a much-improved replacement for older vehicles/transmissions originally using previous Dexron fluids
- Improved performance over previous Dexron fluids in: friction durability, viscosity stability, aeration and foam control, and oxidation resistance
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Last update on 2022-05-21 / Affiliate links / Images from Amazon Product Advertising API
Last update on 2022-05-21 / Affiliate links / Images from Amazon Product Advertising API
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