GM 6L transmission


The 6L XX family is a series of 6-speed longitudinally-mounted automatic transmissions produced by General Motors. The 6L 80 and 6L 90 were assembled at GM Powertrain plants in Ypsilanti, MI, Toledo, Ohio and Silao, Guanajuato, Mexico, while the smaller 6L 45 and 6L 50 were produced at those same Toledo and Silao plants, as well as at a GM Powertrain plant in Strasbourg, France. All four models feature clutch to clutch shifting, eliminating the one-way clutches used on older transmission designs.
It uses a Lepelletier gear mechanism, an epicyclic/planetary gearset, which can provide more gear ratios with significantly fewer components. This means the 6HP 26 is actually lighter than its five-speed 5HP predecessors.
The series was first launched with the 6L 80 in the 2006 Cadillac STS-V, with the remaining three versions all first appearing in 2007 model year vehicles. The 6L 90 was a strengthened and uprated version of the 6L 80, used primarily in heavy-duty truck/van applications. The 6L 50 was used on V8-powered versions of the Cadillac STS sedan and Cadillac SRX crossover, and replaced the 5L 40-E and 5L 50 in GM's lineup. The 6L 45 was a smaller version of the 6L 50, used in certain BMW vehicles and the Cadillac ATS, as part of either rear-wheel drive and all-wheel drive powertrains.

Key Data



Specifications

Technical Data



Combined Parallel and Serial Coupled Gearset Concept For More Gears And Improved Cost-Effectiveness

Main Objectives

The main objective in replacing the predecessor model was to improve vehicle fuel economy with extra speeds and a wider gear span to allow the engine speed level to be lowered. The layout brings the ability to shift in a non-sequential manner – going from gear 6 to gear 2 in extreme situations simply by changing one shift element.

Extent

In order to increase the number of ratios, ZF has abandoned the conventional design method of limiting themselves to pure in-line epicyclic gearing and extended it to a combination with parallel epicyclic gearing. This was only possible thanks to computer-aided design and has resulted in a globally patent for this gearset concept. The 6L is based on the 6HP from ZF, which was the first transmission designed according to this new paradigm. After gaining additional gear ratios only with additional components, this time the number of components has to decrease while the number of ratios still increase. The progress is reflected in a much better ratio of the number of gears to the number of components used compared to existing layouts.


Gearset Concept: Quality

The ratios of the 6 gears are evenly distributed in all versions. Exceptions are the large step from 1st to 2nd gear and the almost geometric steps from 3rd to 4th to 5th gear. They cannot be eliminated without affecting all other gears. As the large step is shifted due to the large span to a lower speed range than with conventional gearboxes, it is less significant. As the gear steps are smaller overall due to the additional gear, the geometric gear steps are still smaller than the corresponding gear steps of conventional gearboxes. Overall, therefore, the weaknesses are not overly significant. As the selected gearset concept saves up to 2 components compared to 5-speed transmissions, the advantages clearly outweigh the disadvantages.
It has a torque converter lock-up for all 6 forward gears, which can be fully disengaged when stationary, largely closing the fuel efficiency gap between vehicles with automatic and manual transmissions.
In a Lepelletier gearset, a conventional planetary gearset and a composite Ravigneaux gearset are combined to reduce both the size and weight as well as the manufacturing costs. Like all transmissions realized with Lepelletier transmissions, the 6L also dispenses with the use of the direct gear ratio and is thus one of the very few automatic transmission concepts without such a ratio.


Applications

6L 45

6L 50

6L 80

6L 90

  • 2007–2014 Chevrolet Silverado 2500HD/3500 HD 6.0
  • 2007–2014 GMC Sierra 2500HD/3500HD 6.0
  • 2010–2023 Chevrolet Express 2500–3500
  • 2010–2023 GMC Savana 2500–3500
  • 2008–2019 Chevrolet Suburban 2500
  • 2009–2013 Cadillac CTS-V
  • 2012–2015 Chevrolet Camaro ZL1
  • 2015–2019 Chevrolet Silverado 2500HD/3500 HD 6.0
  • 2015–2019 GMC Sierra 2500HD/3500HD 6.0
  • 2020–2023 Chevrolet Silverado 2500HD/3500 HD 6.6 L8T
  • 2020–2023 GMC Sierra 2500HD/3500HD 6.6 L8T