In the annals of automotive history, there is a litany of ill-fated replacements to improve upon the manual gearbox. From Citroen’s semi-automatic gearbox in the DS, to the Tiptronic system of 1990’s Porsches, the attempts by various manufacturers to offer the performance and driver engagement of a manual with the ease and convenience of an automatic have universally failed. For a time, it looked as if the dual-clutch transmission had finally achieved this synthesis, but outside of performance applications, they proved disappointing. Balky starts, jerky shifts and a reputation for sub-par reliability marred the adoption of these units. It looks as if the great equalizer has come in the form of a tried and true torque converter automatic transmission.
A TTAC reader is an engineer with a major powertrain company, and offered his extremely detailed analysis of the ZF 9-speed. Consider this an AP level course in powertrain engineering.
Before we dive right in to the 9-speed gearbox, let’s take a quick refresher on the basics of gears. The simplest gear set consists of 2 parallel gears mounted on 2 parallel shafts. Shown in Fig.1 is a gear set with a 20 tooth drive gear on the right and a 30 tooth driven gear on the left. For this gear set the speed of the driven gear is 1.5 times lower than the drive gear, and assuming no frictional losses anywhere, the torque on the driven gear is 1.5 times higher. This gear set has a ratio of 1.5:1. This type of a gear set is usually not favorable for packaging since it requires 2 parallel shafts, and there are largest separating forces that push the 2 gears apart which means that the bearings supporting the shafts have significant radial loads on them, in addition to an axial load if the gears are helical.
In a week we will post our first full review of the all-new and all-controversial 2014 Jeep Cherokee. The new Jeep isn’t just raising eyebrows for the love-it or hate-it styling. Or the resurrection of the Cherokee badge. Or the constant delays in production. Or the transverse mounted engine. Or the lack of solid axles. None of that laundry list seems to cause as much discussion around the automotive water cooler than ZF’s 9HP 9-speed transmission. Click past the jump for a deep dive into the tranny with more speeds than my bicycle. If you don’t want to explore transmissions in detail, don’t click. You have been warned.
Car shopping used to be so simple: you could buy a truck or a car. Then came the wagon, minivan, sport utility and the latest craze: the crossover. There’s just one problem with the crossover for me however: it’s not a crossover. With a name like that you’d assume that a modern crossover blended the lines between a truck/SUV with a car/minivan. The reality of course is that the modern three-row crossover is just a front-driving minivan that doesn’t handle as well or haul as much stuff. In this sea of transverse minivans in SUV clothing lies just one mass-market vehicle that I can honestly call a three-row crossover: the Dodge Durango. Instead of a car that’s been turned into an AWD minivan with a longer hood, the Dodge uses drivetrains out of the RAM 1500 combined with a car-like unibody. While rumors swirled that the Durango would be canceled in favor of a 7-seat Jeep, Dodge was working a substantial makeover for 2014. (Read More…)
ZF Friedrichshafen AG and Levant Power Corp., a Woburn, Massachusetts technology company spun off from MIT, have announced what they call the first fully active suspension system that includes a regenerative function that recovers energy from the motion of the suspension. The system is branded GenShock. Active suspensions are not new, General Motors experimented with an actively suspended ZR-1 Corvette when the automaker owned Lotus, which had worked with active suspensions before the technology was banned in Formula One. Going back even farther, there were the hydropneumatic Citroens and the last true Packards’ “torsion level” suspension. With road cars the goal in using such a system would be to combine good ride with good handling, soft sometimes and stiff sometimes, depending on the driving circumstances. Early tries at developing what chassis engineers call a “high bandwidth active suspension”, capable of dealing with those varying circumstances, have run into cost, complexity and power consumption issues. The GenShock system is claimed to be affordable, simple to integrate in existing suspension designs, and not only have modest power consumption but also be able to recover energy from the suspension.
The 1941 Plymouth Special Deluxe sedan Junkyard Find that I bought from the Brain-Melting Colorado Junkyard last fall now has the body off the frame and is awaiting a Lexus SC400 suspension subframe swap. After much debate about what engine/transmission combo to use in this Hell Project (the plan is to build it to Pikes Peak International Hill Climb specs, while retaining a grimy-looking rat-roddish character), I decided to go with the GM Vortec 4200 aka LL8 L6 engine, with turbocharging added, and that meant that I’d need to find a manual transmission that can withstand at least 400 ft-lbs of torque. Since the Vortec 4200 never came with a manual transmission, and the pseudo-bolt-on Aisin-based 5-speed out of the Solstice and Colorado can’t take the sort of power I’m hoping to get (thus forcing me to go the machine-shop bellhousing-adapter/custome-flywheel route), I was looking for a Borg-Warner T-56 out of a fourth-gen GM F-body, or maybe a Tremec TKO out of a fourth-gen Mustang. Then, an ad for a ZF S6-40 6-speed showed up on Denver Craigslist, with a very reasonable asking price. (Read More…)
GM and Ford will be working together to bring 9 and 10 speed transmissions to market. Reuters reports that the two companies will jointly develop the gearboxes for both front and rear-drive applications, and expect to use them in cars, trucks and SUVs.
What do the Volvo XC60 and Lexus RX F-Sport have in common? Not much. Yet. Today’s vehicles aren’t just built on “modular” platforms, sharing parts with other vehicles from the same manufacturer, they are also “parts bin creations.” You’ll find the same power mirror switch in a Chevy, Jeep, Peugeot, Citroën, Lancia, Lincon and many more. That’s because car parts are like Lego pieces, made by a handful of car parts companies and designed to be everything for everyone. It’s cheaper for everyone to design one switch, one control module, one key fob and just alter some of the plastics and a connector to suit your new car design.
ZF’s 9-speed transmission seems to be gaining popularity with storied off-road name plates that are now marketing unibody vehicles better meant for the urban jungle. The Range Rover Evoque is the next recipient of the ZF 9-speed, which should help squeeze some more efficiency out of the Evoque’s boosted four-cylinder engine.