[Federal Register Volume 63, Number 36 (Tuesday, February 24, 1998)]
[Notices]
[Pages 9294-9295]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 98-4627]
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DEPARTMENT OF TRANSPORTATION
National Highway Traffic Safety Administration
Denial of Motor Vehicle Defect Petition
AGENCY: National Highway Traffic Safety Administration (NHTSA),
Department of Transportation.
ACTION: Denial of petition for a defect investigation.
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SUMMARY: This notice sets forth the reasons for the denial of a
petition submitted to NHTSA under 49 U.S.C. 30162, requesting that the
agency commence a proceeding to determine the existence of a defect
related to motor vehicle safety.
FOR FURTHER INFORMATION CONTACT: Dr. George Chiang, Office of Defects
Investigation, NHTSA, 400 Seventh Street, SW, Washington, DC 20590.
Telephone: (202) 366-5206.
SUPPLEMENTARY INFORMATION: Mr. and Mrs. Scott Montreuil of Ramsey,
Minnesota, submitted a petition dated October 1, 1997, requesting that
an investigation be initiated to determine whether 1993 Chrysler Jeep
Grand Cherokees contain a defect related to motor vehicle safety within
the meaning of 49 U.S.C. Chapter 301. The petition alleges that 1993
Chrysler Jeep Grand Cherokees have a defective viscous coupling that
could cause the steering to bind and lock up, and possibly affect the
vehicle's braking.
Although not all Jeep Grand Cherokees utilize a viscous coupling,
some 1993 through 1995 Jeep Grand Cherokees are equipped with a Quadra-
Trac transfer case. An integral part of the Quadra-Trac transfer case
is its viscous coupling, a speed-sensitive device that controls torque
output between the front and rear drive shafts.
[[Page 9295]]
The housing of the viscous coupling contains high viscosity silicone
fluid and specially engineered metal plates splined alternately to an
inner and outer drum. When there is a difference in front-to-rear axle
speed, such as when the rear wheels slip, the resulting friction
between the metal plates increases the temperature inside the unit.
This causes the fluid to expand, building pressure that moves the
plates together. This occurs almost instantaneously in two modes: the
``shear'' mode, when momentary speed differences occur such as in
cornering or tight turns, causing the plates to move near each other,
or the ``hump'' mode, when high-speed differences occur for a longer
period of time, such as in deep snow or on off-road trails, causing the
plates to lock and the front and rear drive shafts to turn at the same
speed for maximum traction. As traction is gained, the fluid cools, and
the plates separate.
When the viscous coupling fails, it may remain in one of the above
two modes all the time, regardless of whether there is a difference
between front-and-rear axle speed. If the coupling fails in the
``hump'' mode on dry pavement, it may cause vehicle hopping/bucking
during turns, resulting in rapid wear of tires.
NHTSA drove a Jeep Grand Cherokee with a simulated failure of the
viscous coupling in the ``hump'' mode on dry pavement at various
speeds. Some hopping/bucking was experienced while the vehicle executed
turns. However, no steering or braking problems were experienced at any
time.
A review of agency data files, including information reported to
the Auto Safety Hotline by consumers, indicated that, aside from the
petition, there were no other reports concerning failure or malfunction
of the viscous coupling in 1993 Jeep Grand Cherokees. There was a
report pertaining to transmission lockup when the engine was started,
but this was not related to a failure of the viscous coupling.
Chrysler Corporation has received 40 complaints concerning failure
or malfunction of the viscous coupling in the transfer case of 1993
Jeep Grand Cherokees. Five of these complaints report handling
problems, such as vehicle hopping during turns. The remaining 35
complaints are solely related to financial assistance issues. No
crashes or injuries were reported.
The agency has analyzed available information concerning the
problem alleged in the petition. Based on its understanding of viscous
couplings, NHTSA believes that the failure or malfunction of the
viscous coupling in the subject vehicles cannot cause lockup of the
steering or adversely affect the brake system.
For the reasons presented above, it is unlikely that NHTSA would
issue an order for the notification and remedy of a safety-related
defect in the subject vehicles at the conclusion of the investigation
requested in the petition. Therefore, in view of the need to allocate
and prioritize NHTSA's limited resources to best accomplish the
agency's safety mission, the petition is denied.
Authority: 49 U.S.C. 30162(d); delegations of authority at CFR
1.50 and 501.8.
Issued on: January 29, 1998.
Kenneth N. Weinstein,
Associate Administrator for Safety Assurance.
[FR Doc. 98-4627 Filed 2-23-98; 8:45 am]
BILLING CODE 4910-59-M
