Fleet Maintenance - 14

"The transmission fluid pressure sensor, for
example, notifies the driver of low oil conditions
to prevent gear burn-up," Parietti says. "Smart
prognostics for clutch replacement helps to better
plan maintenance schedules. The electrical
system is fully encased, minimizing exposure
and corrosion to wires and connections. A vehicle
oil-coalescing air filter protects the transmission
system from contamination."
Benefits aside, there are some things fleets need
to keep in mind when maintaining an AMT.

		┬╗The PACCAR 12-speed
automated transmission
found on both Peterbilt
and Kenworth trucks
is ideal for linehaul
applications. The
company says the
transmission can
greatly reduce
Photo courtesy of Kenworth

Importance of electrical systems

AMTs are shifted either pneumatically or electrically. With respect to electrically shifted AMTs, battery
maintenance becomes even more important.
Eaton's Pfister says battery life normally ranges
from 12 to 36 months on trucks with a manually
shifted transmission. When operating a truck with
an electrically shifted AMT, that range may top
out at 18 months.
"Heavy electrical draw can affect battery life,
which may be the case with an electrically shifted
AMT," Pfister explains.
Beyond battery maintenance, fleets should
inspect the electrical system on a regular basis,
looking for things like corrosion, wire chafing, and
loose connections.
Whether the AMT is electrically shifted or pneumatically shifted, diagnostic information plays an
important role in AMT operation. Pfister shares
challenges fleets may face if a data link - which is
the connection between different vehicle computer modules - is not operating properly.
"When not functioning properly, data links
can cause undesirable vehicle launches and
shifting issues after launch," Pfister says. "Many
new vehicles have an extremely high bus load
on the data link, which can cause error messages
if any of the electronic control units are improperly functioning or if the physical wiring of the
data link has been compromised. Newer vehicles in the last few years have incorporated two
different Baud Rate data links, 250K and 500K,
which has lessened some of the issues we have
seen in the past."
It is important that technicians receive the
proper training for the particular AMTs they are
working on.
"Training is essential to accurately diagnose
and repair these systems in a safe and timely
manner," Pfister adds.

High-quality air required

The air system is critical to pneumatically shifted
AMTs. Technicians need to be especially vigilant with moisture and other contaminants in
the system.
"Regular inspection and maintenance of the
air dryer is essential," Eaton's Pfister says. "Many
fleets do not replace the desiccant cartridge during
routine maintenance; some wait until the dryer
fails. When that happens, the air system has
already been ingested with moisture, which can
be catastrophic with an AMT. Moisture in the
system can result in harsh shifting or even a loss
of shifting completely."

14 Fleet Maintenance | May 2020

it's a good idea
for fleets to think
about a two-year
service interval on
the oil-coalescing
filter. That said,
technicians need
to keep an eye on
it before that."
Rich Nagel, director of marketing and
customer solutions - air charging for
Bendix Commercial Vehicle Systems

From an air supply standpoint, Bendix's Nagel
says most of the industry's focus has been on dry
air over the past several years. With an AMT, the
goal must be quality air, which extends beyond
just keeping moisture out of the system.
"When I see product come back from the field, I
often see what I refer to as a congealed mix," Nagel
says in reference to a water-oil mix along with
some carbon buildup. "That's why we've shifted
from a focus on dry air to quality air over the past
couple of years."
Automated systems like AMTs are controlled
by solenoid valves and electronic control units
(ECUs), as opposed to air pressure and springs.
That is why quality air is so important.
"With solenoid valves, a 12V coil creates a
magnetic force," Nagel explains. "Inside is an
armature [push pin] that takes the magnetic field
and holds the plunger open and closed. The sliding
bearing inside of the armature has very tight tolerances. But with all of that is an increased chance
of contamination.
"These valves also have smaller orifices," Nagel
continues. "These orifices are susceptible to
contamination which can be a mix of oil passing
from the compressor or oil passed with water if
the dryer isn't removing moisture properly. You

could also experience particle contaminants or
carbon-based contaminants."
Ultimately, the shifting force of an electrically
controlled valve is not as strong as a traditional
pilot-operated valve controlled by air pressure.
"With electrical power, you have a lot less seating force," Nagel says. "You can't just plow through
a piece of dirt or gunk of oil."
That is why oil-coalescing filters used in a vehicle's air compressor have become increasingly
important with AMTs.
"Essentially, any truck you buy today with an
AMT will likely come out of the factory with an
oil-coalescing filter," Nagel points out.
Filter maintenance is important. With a traditional air dryer cartridge, Nagel says the typical
failure mode is the desiccant cartridge getting
dirty. Technicians need a different mindset with
oil-coalescing filters.
"A brand-new oil-coalescing filter may remove
98 percent of the oil aerosols coming out of the
compressor," Nagel says. "But performance
degrades over time. The filter will still work
great, but not as well depending on factors such
as compressor condition, duty cycle, and the way
the truck is being run in general. Regardless, it's
a good idea for fleets to think about a two-year
service interval on the oil-coalescing filter.
That said, technicians need to keep an eye on
it before that."
Also on the topic of air supply, Volvo's I-Shift
AMT utilizes pneumatically actuated clutch and
shift cylinder assemblies. This requires the transmission to have a dedicated air supply.
"The transmission reservoir is supplied with
air from the primary air system's compressor,
and is equipped with a reverse-f low check
valve to prevent loss of transmission air pressure in the event of a primary system failure,"
Volvo's Murickan explains. "The reservoir is
also equipped with a Schrader valve to allow
the tank to be filled manually, if needed. All
of this comes standard with specifying a Volvo
I-Shift transmission."
Preventive maintenance should confirm no
leaks or blocks within air passages. "It is imperative that strict air system maintenance is adhered
to," Murickan adds.


Fleet Maintenance

Table of Contents for the Digital Edition of Fleet Maintenance

Uptime: Expecting the unexpected
Editor's Note: Catching up on fleet maintenance
Maintenance considerations for manual versus automated manual transmissions
DPFs: Clean or replace?
Why Identify and track vehicle warranties?
Lube it or lose it
OTA: Supporting uptime remotely
Management: How fleets can benefit from having a SAMP
Training: Supporting today's students and tomorrow's techs
Diagnostics: Assessing aftermarket diagnostic solutions
Fleet Part & Components
Tools & Equipment
Guest Editorial: Keeping tire pressure at optimum levels
Fleet Maintenance - 1
Fleet Maintenance - 2
Fleet Maintenance - 3
Fleet Maintenance - 4
Fleet Maintenance - 5
Fleet Maintenance - 6
Fleet Maintenance - 7
Fleet Maintenance - Uptime: Expecting the unexpected
Fleet Maintenance - 9
Fleet Maintenance - Editor's Note: Catching up on fleet maintenance
Fleet Maintenance - 11
Fleet Maintenance - Maintenance considerations for manual versus automated manual transmissions
Fleet Maintenance - 13
Fleet Maintenance - 14
Fleet Maintenance - 15
Fleet Maintenance - 16
Fleet Maintenance - 17
Fleet Maintenance - DPFs: Clean or replace?
Fleet Maintenance - 19
Fleet Maintenance - 20
Fleet Maintenance - 21
Fleet Maintenance - 22
Fleet Maintenance - 23
Fleet Maintenance - Why Identify and track vehicle warranties?
Fleet Maintenance - 25
Fleet Maintenance - 26
Fleet Maintenance - 27
Fleet Maintenance - 28
Fleet Maintenance - 29
Fleet Maintenance - Lube it or lose it
Fleet Maintenance - 31
Fleet Maintenance - 32
Fleet Maintenance - 33
Fleet Maintenance - OTA: Supporting uptime remotely
Fleet Maintenance - 35
Fleet Maintenance - Management: How fleets can benefit from having a SAMP
Fleet Maintenance - Training: Supporting today's students and tomorrow's techs
Fleet Maintenance - Diagnostics: Assessing aftermarket diagnostic solutions
Fleet Maintenance - 39
Fleet Maintenance - Fleet Part & Components
Fleet Maintenance - Tools & Equipment
Fleet Maintenance - Guest Editorial: Keeping tire pressure at optimum levels
Fleet Maintenance - 43
Fleet Maintenance - 44