ZF Develops 8-Speed Automatic Transmission for Passenger Cars; 6% Additional Fuel Savings, and Support for Hybridization
02 May 2007
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| The basis of the new ZF automatic transmission generation is a new transmission concept featuring four planetary gear sets and five shift elements. |
ZF has designed a new 8-speed automatic transmission for passenger cars based on a new transmission concept featuring four planetary gearsets and five shift elements. The automatic ZF 8-speed transmission enables additional fuel savings of approximately six percent compared to the current generation of 6-speed transmissions. Compared to a 5-speed, the new 8-speed reduces fuel consumption by about 14%.
At the same time, the automatic 8-speed transmission transmits more power in comparison to the previous model, but uses the same installation space and does not require more components.
Our main development target was to find a transmission concept which allows for significant additional fuel consumption reduction and thus offers tangible added value to our customers and drivers without making any compromises in terms of performance. The number of gears was not given top priority.
—Dr. Michael Paul, ZF Executive Vice President, Technology and Group Executive of the Car Driveline Technology division
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| Better transmission spreading and a significantly better internal efficiency allow for consumption savings of up to six percent in the new ZF automatic 8-speed transmission compared to the direct predecessor model with six speeds. Click to enlarge. |
In the new design based on the four planetary gearsets and five shift elements, only two shift elements are opened in each gear which leads to considerably lower drag losses.
Besides the improved internal efficiency, this transmission concept features a higher total ratio. Modern torsional vibration damping systems in the torque converter also have a positive impact on consumption and CO2 emissions. These systems also allow for a quick lock-up of the converter clutch in the second generation automatic 6-speed transmission presented in 2006. Furthermore, ZF now uses a small vane cell pump mounted parallel to the axle.
Another development focus was the increase in performance. The power-to-weight ratio of the new automatic transmission is higher and can transmit a higher input torque at the same weight, in comparison to the previous model. In terms of shift comfort, response and shifting speed, also the new automatic 8-speed transmission operates at the already very high level of the second generation of the automatic 6-speed transmission.
The new transmission has been designed in such a way that it can serve as a modular system for hybrid and all-wheel applications without changing the basic transmission concept.
A torque converter could be replaced by new clutches or could be omitted completely when an integrated starting clutch is used. The design engineers of the automatic 8-speed transmission have also paid attention to the compatibility with today’s and future ZF all-wheel concepts.
For the hybridization of the driveline, the automatic 8-speed transmission offers the possibility of implementing both a micro hybrid with a crankshaft starter generator and a full hybrid in the form of a parallel hybrid. All known hybrid functions can thus be implemented in combination with the new automatic 8-speed transmission.
AND, it will make a mean cup of joe!
Posted by: k | 02 May 2007 at 12:00 PM
One reason both ford and g, have looked into e drive is to chuck the trans altogether. They dont say it but most times transmissions get much more spendy and more maintenance is needed for each added gear.
Posted by: wintermane | 02 May 2007 at 12:25 PM
I once had a ZF transmission in an old Volvo, and the thing was a LEMON. You could blow out the seals on the thing if you idled it in neutral at too high of an RPM, which is exactly what they do during emissions testing.
I have had a manual ever since. I really prefer a manual over a slushbox anyways...
Posted by: eric | 02 May 2007 at 01:09 PM
I'd rather see twin clutch DSG systems, slushboxes waste engine power and fuel.
Posted by: Tim Russell | 02 May 2007 at 02:05 PM
ZF Makes some of the premier transmissions in the World, including some great automated manual transmissions for Big Rigs (Like Kenworth!)
They also make manual transmissions for Ford and GM heavy duty diesel pickup trucks. They have a good track record. I wanted to state this, because who knows what the previous poster's VOLVO had gone through? Was it maintained? How many miles did it have on it?
Anway, if cost isn't an issue, then yes DSG is a better solution. But if the cost for this is the same as the 4 to 6 speed units out there now, this is a logical replacement. Good work ZF.
Posted by: Spokane Walt | 02 May 2007 at 02:48 PM
I agree with Wintermane; let's shift to electric motors and do away with this horrendously expensive and complicated transmission stuff. Not to mention the horrendously expensive and complicated internal combustion engine!
Posted by: JN2 | 02 May 2007 at 03:16 PM
The Volvo trans problem is a known issue with those models. At least I've heard of this before from a few Volvo owners.
The cars I drive have ZF auto trans in them and they are pretty robust.
Posted by: Rich | 02 May 2007 at 04:49 PM
Wintermane and JN2;
The idea of an electric drive line instead of complicated and convoluted automatic transmissions is heresy against the Gods of mechanical engineers. The law is all mechanics are suppose to become more and more involved with time. Too take the approach to simplify using electric devices breaks that law, well! now I just don't know!...ha!
Posted by: Lad | 02 May 2007 at 06:01 PM
Transmission efficiencies need to be compared to a reference. I would take that as an engaged gear set from a manual transmission. Any of these manuals do NOT HAVE a 14% efficiency higher than even the poorest modern automatic, so there is highgly unlikely the "additional 14% efficiency" to be gotten.
I suspect this is Public Relations fluff created in the press department rather than the engineering department, which knows this CANNOT be the case.
The only way to even postulate a 14% gain is to have a seldom engaged highest gear ratio as a super duper overdrive at .45 to 1 or so, over the typical highest overdrive of .6 to 1.
Posted by: Stan Peterson | 05 May 2007 at 09:14 AM