Review: ZF transmission is a great 8

Jim Park
The PowerLine 8 transmission from ZF is new to North America, but more than 15 million copies are currently running all over Europe and Asia. (ZF photo)

TORONTO, Ont. — Medium-duty truck builders will soon have a new transmission to add to their data books.

In early 2021, German automotive supplier ZF Friedrichschafen AG will launch the PowerLine 8AP, an eight-speed torque-convertor automatic transmission medium-duty and vocational applications with gross vehicle weights up to 26,000 kg (57,000 lb).

The PowerLine 8AP was officially introduced to the North American market in mid-2018, and then demonstrated to trade press editors a year later at an event at the Transportation Research Center near East Liberty, Ohio. It’s new to us, but more than 15 million copies of this transmission have been operating in passenger cars (fitted with the scaled-down 8HP version) across Europe and Asia.

The 8AP is a “muscled-up” version of that same platform. ZF says little of the transmission’s basic design was changed in scaling it up for service in Class 3 through 8 trucks, except to build in some extra durability.

ZF still hasn’t said which truck maker(s) would be first to market with the PowerLine 8AP.

The transmission boasts some impressive spec’s and features, but performance will likely be its biggest selling feature. ZF says the transmission offers 30% better acceleration than other automatic transmissions and a 45% weight advantage — the PowerLine 8 weighs a paltry 328 lb. (149 kg).

“The PowerLine is at least — not up to — at least 10% better on fuel than any competitive product in same application,” said Andre Kohl, ZF’s North American business development manager, while introducing the product.

Kohl also pointed out that the transmission is ready for what the OEMs will be asking for in terms of meeting the pending GHG Phase II emissions regulations. For example, it has an integrated stop/start assist feature that shuts off and starts the engine while at traffic lights.

“We incorporate an accumulator inside the transmission to help with restarting,” he said.

Starting out, it will launch in first or second gear, depending on the load, and it will skip-shift when the opportunity presents itself. It has a neutral idle feature that disengages the torque convertor to take the load off the engine when the truck isn’t moving. Gear ratios range from 4.89 in first to 0.64 in eighth, which is like a double or maybe triple overdrive. There’s plenty of latitude in the eight cogs for any driving condition, and ZF did say that fuel economy was a prime driver in the engineering process.

It also features twin torsional dampers, which will help with downsped powertrains. These are more common to on-highway Class 8s, but Kohl says downspeeding is coming to medium-duty as part of the solution to GHG Phase 2. There’s also a lock-up clutch in first gear for improved energy efficiency. With the PowerLine 8, the torque convertor is used only to launch and stop the truck.

On the maintenance side you get “best in class” extended oil-change intervals, and Kohl said the oil filter is good “for life”. It also features a fully integrated control unit inside the casing, with no external sensors or harnesses. That should help with durability.

During the showcase event in June, I drove two trucks equipped with the PowerLine 8, and one “baseline” truck for comparative purposes. It was impressive.

A few laps around the track

Driving the PowerLine 8 proved pretty well everything Kohl said during his presentation.

Sitting at a stop in first gear, the transmission goes into a false neutral of sorts. The shifter interface indicates it’s in gear, but the engine idles freely. The torque convertor engages only when you apply the throttle, so you don’t have to stand on the brake pedal to keep it from rolling away. The launch is spectacularly smooth, and the upshifts are almost imperceptible. You literally cannot feel the transmission shifting gears. You can tell the shifts are happening based on the sound of the engine, but they are very quick and really smooth, and there’s never a lag in torque as you accelerate.

The downshifts were a little more noticeable. But because of the closer ratios between the eight gears on the PowerLine transmission compared to the baseline six-speed transmission, the shifts weren’t quite so jarring. Drivers will certainly appreciate that at the end of a long day. Many of the people who will be operating this transmission will be non-CDL holders, and more accustomed to the automotive-like feel that it delivers.

I did a few laps on the track and got the trucks up to speed. One truck was loaded to a 37,000 lb. gross vehicle weight, while the other was empty. The lighter one naturally got up to speed more quickly, but the loaded truck wasn’t far behind. The acceleration was as Kohl promised. In top gear the driving environment was pretty quiet because the engine was revving so low.

The PowerLine transmission did a great job of selecting the right gear in transient driving conditions and stop-and-go operation. I noticed virtually no hunting, pecking, or second-guessing its choices. It always seemed to be in the right gear for the moment.

The transmission’s stop-start feature is particularly interesting, as the unit automatically and seamlessly shifts out of Drive to Neutral after three seconds – when stopped at a traffic light, for example. This reduces the amount of torque the transmission produces, and as a result, the amount of fuel an engine has to burn to maintain those torque levels. ZF engineers say an average vocational fleet engaged in city and urban delivery applications can see up to a 5% boost in fuel economy thanks to this single feature.

Additionally, with optional predictive shifting, sailing, and stop-start capabilities, the Powerline is both ready for vocational fleet operations today and prepared for electric-hybrid transmissions in future zero- and near-zero emission trucks. “Sailing” is ZF’s term for when the transmission automatically shifts into neutral on downgrades to save fuel.

The most remarkable part of the demonstration ride came during an off-road loop at TRC site, featuring a hill with a 23% grade. The loaded truck walked right up that grade from a full stop at the bottom. It also competently managed a launch from a full stop when midway up the grade. It even managed an upshift from first to second on one of my runs up the hill, with full throttle applied right from the start.

Drivers won’t see many such hills in the real world, but it’s nice to know that the transmission could handle one with very little effort.

I had driven the PowerLine transmission three years ago in a Dodge Ram half-ton pickup truck while on a press junket in Germany. I wasn’t aware at the time that the transmission could be scaled up to medium-duty weight ranges of up to 57,000 lb. In hindsight, the transmission performed remarkably well in both the pickup truck back in 2016 and the Peterbilt in 2019.

Additional Powerline features

  • Up to 1,000 lb-ft input torque
  • 485 lb-ft engine-driven dual side PTO interface
  • Patented eight-speed gear set and intelligent skip-shift to improve acceleration performance by up to 30%
  • Smart software features such as Adaptive Starting Gear, Neutral Idle Control, Multi Skip Shift, Maneuvering Mode, Stop-Start, and more
  • Fuel efficiency performance provides significant savings of more than 10% over available automatic transmissions
  • 45% lighter than comparable products
  • 328 lb. (149 kg) dry weight
Jim Park

Jim Park was a CDL driver and owner-operator from 1978 until 1998, when he began his second career as a trucking journalist. During that career transition, he hosted an overnight radio show on a Hamilton, Ontario radio station and later went on to anchor the trucking news in SiriusXM's Road Dog Trucking channel. Jim is a regular contributor to Today's Trucking and, and produces Focus On and On the Spot test drive videos.

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  • I vividly remember the ZF transmission installed in 7 series Volvo of the 80s and early 90s . We sold remans like bubble gum! The trusty Asian Warner s went to the crusher in the car originally installed!