#GM8l90Transmission

On the surface, there are many similarities between the ZF 8HP transmission family and the GM 8L90. Namely both use 4 gear sets, 5 shifting elements (3 clutches and two brakes), off axis pumps, and have roughly the same gear ratio spread at about 7:1 overall spread. The saturation dive is not about dealing with things that are on the surface. To be entirely honest as the details started to emerge on the GM 8L family of transmissions I suspected that it would end up being a ZF licensed design, the ZF 8HP after all is a very good design in my opinion. But the abstract of the paper that we managed to snag before SAE took it down revealed one very important detail – all 3 of the clutches were located in front of the planetary gear sets very much unlike the ZF design.

It’s not known if the leak was intentional or not, but the summary of a paper initially published by the Society of Automotive Engineers, since taken down from the SAE site, says that a new eight speed automatic transmission, given the designation 8L90 by General Motors, will be introduced in the 2015 Corvette, on sale next fall. The all-new 7th generation Corvette is currently offered with GM’s 6L80 six speed automatic and a seven speed manual gearbox. The 8L90 is described as being designed for rear-wheel-drive applications and variants will likely be used in GM’s fullsize pickups and in rear wheel drive Cadillacs.

The 8L90 has about the same overall dimensions as the 6L80, and is said to be able to handle up to 737 lb-ft of torque. It has a shorter first gear for better launch acceleration, an overall ratio spread of 7.0 and three speed sensors for better shift response. Other benefits are said to be better fuel economy, improved performance and a quieter car with improved NVH levels.