General Motors is recalling 461,839 pickup trucks and SUVs equipped with diesel engines because of a potential transmission issue that could cause the rear wheels to lock up.
A transmission control valve in the affected vehicles could be susceptible to excess wear over time, according to the NHTSA. This could result in gradual loss of pressure within the valve, which regulates the flow of hydraulic fluid that actuates gear shifts and the coupling of the engine and the driven wheels.
A pressure loss could lead to harsh shifting or, in rare cases, momentary rear-wheel lockup, the NHTSA said. The latter condition occurs specifically when the affected vehicles' 10-speed automatic transmissions downshift from eighth gear to fifth gear.
GM told the NHTSA that it is aware of 11 incidents potentially related to this defect, including some cases of trucks veering off roadways, some of which led to minor property damage. Three minor injuries were reported along with these incidents, although none were associated with a collision, GM said.
The automaker estimates the defect could exist in 1% of the following vehicles, if equipped with diesel engines:
The remedy for this condition is new transmission-control software that will monitor valve performance and detect excess wear. If that excess wear is detected, the software will limit the transmission to fifth gear to prevent wheel lockup. While that condition will not occur, this will also lead to sluggish acceleration. Drivers may also see an engine-service warning light and reduced propulsion message on the dashboard.
Dealers will install the software free of charge, and GM will also reimburse customers who had any repairs stemming from this defect done on their own dime. Owner notification letters will be mailed Dec. 9. Owner can contact GM customer service at 1-888-988-7267 or visit GM's recall page for more information and mention recall number N242454440.
Owners can also try the customer service lines for the individual brands, including 1-800-458-8006 for Cadillac, 1-800-222-1020 for Chevy, and 1-800-462-8782 for GMC.