2010Hydra-Matic 4T65 (M15)

2010 Model Year Summary

Hydra-Matic 4T65 four-speed electronically controlled automatic FWDCar transaxle

  • There are no planned performance upgrades for the 2010Model Year, activities will be centered on quality improvements

Low maintenance

The M15 uses DEXRON® VI fluid, which is validated as “fill-for-life,” and requires no maintenance under normal operating conditions. The ability to tailor the transaxle to specific platform requirements with the wide range of available ratios ensures the transaxle is operated as designed. Finally, the chain and sprocket drive system and the premium material used in the gear sets contribute to very high durability and no requirement for maintenance under normal operating conditions.

Overview

The Hydra-Matic 4T65 (M15) was introduced in 1997, and has applications from mid-sized to large front-drive sedans and minivans, using V-6 and V-8 engines. It is a two-axis automatic four-speed transaxle with electronic controls, and features a unique dual chain and sprocket configuration that runs quieter than a single chain design. A stronger version of the chain, with heat-treated pins, is used with V-8 applications. In addition, for V-8 applications the starter motor is moved from the engine side of the engine/transaxle coupling to the transmission side, and the input sun gears are made with a process that increases durability.The final drive sun gearis double shot-peen with ceramic shot for improved strength and durability. The final drive planetary differential gets a larger pinion gear carrier, and the park position gear gets a stronger bearing. In addition, all pinion gears are made with a process to increase their strength.

The M15is available with two different size torque converters (245mm & 258mm)

There are three final drive ratios and three sprocket ratios, allowing nine separate overall ratios.

The operation of the 4T65 is controlled by either an Engine Control Module/Transmission Control Module combination, or a Powertrain Control Module. These controllers compensate shift timing for normal wear of components, which offers consistent operation for the life of the transaxle. If a driver manually selects a low range, but then fails to upshift at higher speeds, the control systems protect the engine from over-revving by automatically shifting to a higher gear. The controllers also reduce engine spark during abusive shifts that occur during “rocking” maneuvers, such as trying to extract the vehicle from a snow bank by rapidly shifting between forward gears and reverse gear. The control systems protect from overheating by automatically applying the torque converter clutch to reduce heat build-up from fluid shear, and a “limp home” mode allows the driver to operate the vehicle at reduced speed in the event of a transaxle control failure.

Most applications utilize the Engine Control Module/Transmission Control Module configuration The latest module is the T42 Transmission Control Module (TCM), which was introduced in 2004 for the Rendezvous application of the 4T65. This module has more memory and faster processing speed than previous modules, and the new configuration increases the flexibility and capabilities of the vehicle electrical architecture. The T42 utilizes “C” language common software (C-series) which provides a modular structure with stand alone architecture.

GM’s proprietary Electronic Capacity Controlled Clutch (ECCC) technology dampens engine torque pulses and provides a smooth engagement of torque converter lock up, and is integral with all 4T65 applications.

To improve noise and vibration characteristics of the entire engine/transaxle unit, bosses are available in several places on specific 4T65 housings to accept struts and brackets that connect the different engines to the transaxle. These pieces serve to dampen vibration and noise of the entire powertrain unit. Four different locations for the bosses are cast into transaxle cases and different locations are used for each specific engine and platform.