6. GM 6L80E & 6L90E


In 2006 General Motors introduced their new line of the innovative 6L80E transmissions. Unlike previous GM transmissions that evolved from earlier transmission models. GM focused on the objective of designing a new line of transmissions from scratch. The 6L80E would usher in a whole new meaning to electronically controlled hydraulic transmissions.

The implementation of the 6L80E concentrated on designing a new transmission to replace the 4L60E/4L80E transmissions. the 4L60E/4L80E transmissions were basically upgraded and re-engineered transmissions from earlier based models. For example, the 4L60E was based off of the earlier 700R4. Likewise, the 4L80E had its roots from the TH400. Rather than continuing on the path of upgrading older design transmissions to meet modern standards, General Motors Hydra-Matic division embarked on a new project to develop an entirely new family of transmissions. The 6L80E was the 1st transmission to be introduced under this new platform.

Design Concept

The 6l80E was purposely engineered around a modular design concept. The bellhousing and rear tailhousing section are detachable from the main transmission body. This modular design of the 6L80e allows for variations to accommodate different engines and vehicle applications.

The 6l80e is based on three gear assemblies. The three gear set assemblies comprise of an input planetary gear set and two output gear sets. The first compound gear set contains three pairs of two pinion gears on the output carrier. The second assembly meshes with the sun gear, while the third compound gear set meshes with the ring gear. The combined gear sets provide the six forward gear ratios and reverse.

Transmission Control Module

Shifting of the transmission is fully automatic and is accomplished by the use of the 32-bit Transmission Control Module (TCM) contained inside the transmission. The TCM collects and monitors various electronic sensor inputs. It then uses this information to enable the transmission to shift at optimal sequences. The TCM dictates the variable bleed pressure control solenoids to command shift quality and timing. The TCM controls the lock and release of the torque converter clutch. This delivers supreme fuel efficiency without sacrificing vehicle performance. The TCM monitors the performance of the transmission. compensating for wear of components and adjusting accordingly so performance is consistent for the longevity of the transmission

Performance Algorithm Shifting/Braking

Performance Algorithm Shifting is available on some applications. Performance Algorithm Shifting (PAS) monitors how assertively the driver is using engine output to determine at what engine speed to upshift or downshift. The PAS can determine if the vehicle is being driven in an aggressive manner. If the algorithm recognizes this condition, it can initiate downshifts and actuate lower gears for ideal vehicle performance. The PAS can also detect a drop in engine power during an upshift shift. In the chance of possible clutch damage, the PAS will auto correct shift strategy and stabilize the shift sequence. Some truck applications also offer a tow/haul mode. When activated, grade braking and clutch line pressure are initiated.

Driver Shift Control (DSC) – The Driver Shift Control is an additional shift option which allows the driver to manually shift the transmission. When the DSC shift selector lever is actuated, the driver may manually select upshifts or downshifts like a manual transmission. Electronic safeguards are present to prevent the driver from over reviving or accidental shifting.

6l80E Specifics

Case Length .... 23.50”

Case Material ... Aluminum

Output Shaft Spline .... 32

1st Gear Ratio .... 4.02

2nd Gear Ratio .... 2.36

3rd Gear Ratio .... 1.53

4th Gear Ratio .... 1.15

5th Gear Ratio …. .085

6th Gear Ratio …. .667

Reverse: 3.06

Transmission Weight .... 200-230lbs

Fluid Type .... Dextron VI

Adapting The 6l80E

The 6L80E is a prime candidate for conversions in a multitude of vehicle applications. The length of the transmission is remarkably short for a 6 six speed transmission. The wheel base length of some vehicles can limit some conversion applications. We do not recommend using this transmission on CJ5 Jeeps and other similar short wheel base vehicles. On longer wheel base vehicles, this transmission is well suited. The transmission also has a narrow oil pan that allows for better front drive shaft clearance. The 6l80E also has self-contained electronic sensors which allows for easy adaptation. Most of our adapter kits utilize the existing 4wd output shaft, so dismantling of the transmission is typically not required.

Although many 6l80e transmissions share the common 90 degree bolt as older Chevy V8 engines, special consideration should be used on engine selection. The 6l80E is found behind Gen IV and Gen V engines that share advanced computer controls together. At this time, we only recommend using computer controlled engines compatible with the 6l80E.

6l80E vs 6l90E

Within one year of GM introducing the 6l80e, the stronger 6l90E hit the market. This version is 1-3/8" longer and shares 75% of the internal components. Engine torque rating was also slightly increased, but the output torque rating jumped up by nearly 220 ft. lbs. to 885 ft. lbs., GM also raised GVW of 15,000 lbs. and GCVW of 21,000 lbs. The spline counts also changed from 32 to 29. The 6L90e is a heavier-duty version of the 6L80E, Upgrades consisted of a strengthened input gear set and a strengthened wider output gear set. The 6L90E also contains one more clutch plate in each clutch pack than the 6L80 for heavier duty applications.