Technical Service Bulletins

Missing gears

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Missing gears

Some owners of 2009 Chevy Colorado, Express, Silverado or Trailblazer; GMC Canyon, Envoy, Savana or Sierra; Hummer H3 and Saab 9-7x equipped with the 4L60 automatic transmission may complain about a condition of bind when the transmission shifts into fourth gear and/or no second or fourth gears.

During disassembly of the transmission, technicians may find that the 2-4 band and the overrun clutch are both distressed while no other clutches are damaged.

This condition may be caused by the oil seal ring grooves on the turbine shaft being improperly machined. Improperly machined seal grooves can allow forward clutch application to leak fluid into the overrun clutch apply circuit and apply the overrun clutch. This will cause a bind condition between the overrun clutch and the 2-4 band in fourth gear.

If only the 2-4 band and the overrun clutches are distressed and no other clutches are damaged, replace the input housing and turbine shaft assembly during the transmission repair. Failure to replace the input housing and turbine shaft assembly could result in repeat transmission damage.

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