Driveline Technology

Looking down the automotive technology track to 2020, the penetration rate of AWD systems in North America is expected to reach over 80% in the sport utility vehicle segment.
This means that front-wheel-drive-based, all-wheel-drive disconnect systems; true torque vectoring systems; electronic limited slip differential systems; and power transfer units will remain the most important parameters defining future driveline system strategies. For jobbers, this translates into parts, parts, and more parts.
The driveline business experienced its first big change back in the 1980s, when front-wheel drive was introduced. The traditional drive shaft fell by the wayside and the front wheel axle rebuilding market sprang up – and was a very good business until the low-cost offshore market took over.
“We used to rebuild those axles in the ’80s, but gave it up by the ’90s and I don’t miss it one bit. That axle grease doesn’t come out,” jokes Jerry Friesen of Pat’s Driveline in Edmonton, Alberta. Pat’s Driveline operates ten retail facilities across Canada and three major product distribution warehouses and is a member of the Gear Centre Group of Companies.
“When vehicles went to front-wheel drive, we kind of lost that automotive driveshaft market. But now it’s all back. Today, every all-wheel-drive vehicle, whether it’s a Subaru or a Chevy Equinox, has a driveshaft in it.”
This bodes well for jobbers, as more driveline components are developed and brought to market by OEMs looking to improve performance, reliability, and fuel economy.
A vehicle’s front and rear axles determine its drive behaviour, driving comfort, response behaviour, and safety potential. Even individual components such as wheel carriers, sensor systems, wheel suspension and location, crossmembers, stabilizers, suspension, and damping are equally important as the connection between wheels and the body.
Most AWD SUVs are front-wheel drive with an auxiliary shaft out the back for use when it’s needed. For example, in the winter when it gets slippery, that rear axle kicks in to transmit torque when the front wheels are spinning. “That’s when you see the steady bearings and CV joints going bad, and we like that,” says Friesen. “The technology has changed so much. For instance, most U-joints and steady bearings are not designed for replacement in many of the newer vehicles. It’s built in to the driveshaft, so you are looking at replacing the entire driveshaft, which is a very expensive repair.”
To address this costly development, Pat’s Driveline manufactures drive shafts with replaceable components. When they come across a particular drive shaft they can’t manufacture themselves, they will source one that is designed as a replacement at a lower cost than an OEM solution.
For example, the Ford F-150 comes equipped with a drive shaft with non-replaceable steady bearings. “The steady bearings are the weakest part of that driveline. So we build a replacement shaft that matches the weight and mechanics of the original. We can’t beef it up too much, because then you would know you have a drive shaft under there. It has to be very close to the original, and we build it with replaceable parts,” explains Friesen.
The steady bearing is a critical part of the drive system, and probably the weakest link. The rubber dampening of the steady bearing has to be such that it doesn’t transmit the harshness of the drive shaft torsion to the frame.
“There are a lot of new designs out there now. There are soft rubbers with different rebound rates. When the universal joint transmits torque through an angle, it creates forces, and you don’t want those forces transmitting that harshness to the frame. So the steady bearings can’t be too stiff, but they need the appropriate dampening effect,” explains Friesen.
Jobbers should take note of the most popular SUVs in their region, as these will be the ones most likely to be in for service, simply due to the sheer numbers of them on the road.
“A popular one right off the top in the SUV category is the Honda CRV. The Toyota RAV 4 is also becoming more popular. The more popular the vehicle, the higher the frequency we see in driveshaft repairs. The Chevy Equinox is another popular model we see a lot of in the shop,” he adds.
Transmissions have also seen a great deal of change, as OEMs work towards the stringent CAFE (Corporate Average Fuel Economy) requirements. Thanks to technology advancements, the formerly ubiquitous three-speed transmission is now gone, replaced by five- and six-speed units.
“If you look at vehicles in operation between 2000 and 2005, the six-speeds were introduced at that time, and there were fewer than a million vehicles in operation with the six-speed. By 2007 the six-speed crossed the one-million threshold, and by 2013, seven million vehicles in the U.S. were equipped with a six-speed transmission,” explains Bob Roxburgh of King-O-Matic Industries. King-O-Matic is Canada’s largest supplier of transmission and drivetrain components.
“We are also seeing a lot of five-speeds from both the import and domestic OEs. Ford, GM, and Chrysler, for example, have all stepped up and have five- and six-speed transmissions working. The 6L80s and 6L90s have become very popular transmissions,” says Roxburgh. The real trend, though, is the fact that these new transmissions are much more expensive to fix. The parts tend to be more expensive and many of the transmissions are not yet available in the aftermarket; and if they are, they are still expensive. “The higher ticket price on this later technology is forcing customers to decide whether or not to make the repair,” notes Roxburgh.
In response to this growing repair market, dealers have come out with complete unit solutions, jumping into what was traditionally the aftermarket. GM, Ford, and Chrysler in Canada all sell complete rebuilt replacement transmissions. “The traditional transmission industry is still a main supplier, as the price point on the OE rebuilt units isn’t particularly competitive. But they (dealers) are certainly grabbing more of this market than they were four or five years ago,” says Roxburgh.
How critical is it for independent repair shops to keep up with this new technology?
Roxburgh says if you are not keeping up, you will just continue to fall further and further behind. “With the newer units, it’s all about the electronic technology. Shops have to invest in the diagnostics just to determine if the problem they are seeing with a given vehicle is with the transmission.”
With the growth in AWD systems, PTUs (Power Transfer Units) are becoming more prevalent. “For front-wheel-drive vehicles cost is a major concern, because the OEMs have to add disconnects at two locations so the axle won’t spin. For transverse engines and the compact SUV market, those consumers do not want to switch manually, so it’s about how they can get an automated process into it. And this is an extremely difficult challenge,” explains Vikram Chandrasekar, transportation research analyst with Frost & Sullivan.
“The all-wheel-drive units will use something that is somewhat different than a transfer case, either manually or electronically applied. We have not seen enough of them at this point to understand if it’s a weak point or not,” adds Roxburgh.
“What I do see is movement to seven-speed and eight-speed transmissions for improved fuel economy. Aside from the imports, the first eight-speeds that came out were ZF units. Between 2011 and 2013, a significant number of eight-speeds came out, and they are certainly growing in numbers these days. These units are still under warranty, so we haven’t really seen them in the aftermarket yet [see ZF sidebar].
“There are a tremendous number of parts coming down the pipe. For years we would see just a few new units per year, and now we have a tremendous amount of variations on the same themes. We have gone from 40 or 50 key transmissions to at least 100 units with multiple variations and a great deal more complexity,” explains Roxburgh.
“Take the Alison transmission,” continues Roxburgh. “It’s become so complicated that you can’t just put any Alison anywhere, because the controller is in the transmission, so if you put the wrong valve body in with the wrong controller it will shift in a bizarre fashion. Knowledge of these technical details by both parts suppliers and technicians is critical.”
This is where the test equipment comes in. Up until recently, independent repair shops had to go to the dealer to have the new valve body re-flashed. Now with Right to Repair, it can be done independently. A repair shop can subscribe to receive that data and re-flash a transmission valve body or controller to harmonize it. And, if they decide to put in something a little different, they can make it work by re-flashing. nJN

One Transmission – Many Possibilities
For the eight-speed automatic transmission, ZF set out to design and develop
an entirely new gear set concept. The result is a revolution in transmission design: a transmission concept with four gear sets which requires only five shift elements – of which only two are open in any given gear. The 8HP also requires no more than three multi-disk clutches and two brakes, which allows it to achieve a greater degree of efficiency than other concepts. As a result of the fact that only two shift elements are open per gear, drag losses in the transmission are sustainably reduced. This effect is supported by the use of a new parallel-axis vane-type oil pump.
A torque range from 300 to 1000 Newton meters (221 to 737 foot-pounds) makes the 8HP the perfect partner for all rear-wheel-drive and all-wheel-drive designs. Although the 8HP features two more speeds than the 6HP, the dimensions have remained unchanged and the weight was even reduced by 3% to 87 kg (192 lbs.) (transmission modular system 8HP70), including oil. At the same time, the total transmission ratio spread of 7.0 ensures that the engine is always in its optimum operating range. This translates into improved acceleration and reduced fuel consumption.