The Transmission in My 2006 Chevrolet Malibu Has Hard and Delayed Shifts. What’s Wrong?

Q: I have a 2006 Chevrolet Malibu MAXX. The automatic transmission (model 4T45E) exhibits a delayed and harsh shift from first to second and second to third gear, especially under hard acceleration. Once the transmission engages, however, it stays engaged, and the car drives fine.

I changed the fluid and filter, yet the problem persists. Will a diagnostic test tell what’s going on inside of the transmission? Unfortunately, my scan tool does not have this capability.

– Daryl Conley from New Mexico

A: Hello, Daryl. The 4T45E in your car uses a transmission adaptive pressure (TAP) system. With this setup, the transmission control module (TCM) can adapt line pressure to compensate for internal wear to components, such as clutch packs.

The TCM monitors the input speed sensor and vehicle speed sensor to determine how long each shift takes. If the TCM detects a shift is taking longer than it should, the module will bump up line pressure the next time around.

OEM-level scan tools will often display the TAP information as thirteen different cells (numbered 4 through 16). Each cell represents a different load range, as demanded by the driver. For example, cell 4 represents light acceleration, whereas cell 16 represents heavy acceleration.

Failing to reset the TAP values after the transmission has been rebuilt or replaced can result in delayed and/or harsh shifts. This is because the TCM has learned the bad habits from the old, worn-out transmission. So, if the transmission in your car has undergone repair recently, the adaptive values are something to consider.

On the other hand, if your transmission has not undergone recent repair, harsh and/or delayed shifts in select gears could mean that there are worn internal components (e.g., clutch friction discs), and the TCM is bumping up line pressure to compensate for that wear. 

A valve body issue is another possibility. An engine performance problem isn’t out of the question, either, as the TCM relies on information from the throttle position sensor and vehicle speed sensor when calculating shift timing.

I recommend taking the car to a transmission shop for a thorough diagnosis. Sure, you’ll have to pay a fee, but a professional repair facility will have all of the necessary equipment to get to the bottom of the problem.

Good luck!

Product Mentioned in this Guide

Transmission Control Module Valve Body