Auto Tech

GM: Six speeds better than four

GM posts a blog and video about the benefits of its six-speed transmissions.

GM six-speed transmission
GM shows the insides of its six-speed transmission. GM

GM touts its six-speed-automatic transmissions in video and blog form today, highlighting the kind of power train technology that should keep the company competitive. Engineer Jeff Lux provides some insight into GM transmission advances in his blog entry, and another transmission engineer, Scott Damman, narrates a video with some interesting animations showing how these transmissions work.

The blog points out the four percent fuel efficiency that can be gained when using a six-speed transmission over a four speed. GM has nine different six-speed transmissions, and is working on a 10th, with 40 models using them. Those numbers are likely to go down with model and brand cutbacks. We're also not sure why GM needs 10 different transmissions when four should do, such as one for small cars, one for larger sedans and crossovers, one for SUVs, and a performance model for cars like the Corvette. Either the number of transmission shows GM's inefficiency, or the blogger is counting versions with slightly different gearing.

Other work toward improving performance mentioned in the blog involves the software used to control torque converter lock-up, which shows how even power trains are incorporating advanced technology. And we're all for eliminating the slush from automatic transmissions.

Another fuel saving technology GM is rolling out in the Chevrolet Equinox and GMC Terrain is an Eco mode, a button that makes the transmission upshift earlier and hold high gears longer, thus improving fuel economy. Here's a suggestion: make that Eco mode the normal Drive mode.

Click here to read the blog.

This video is entertaining if you like to see how the innards of a transmission look.