P0716: How to Diagnose & Fix — Input/Turbine Speed Sensor "A" Circuit Range/Performance

Behind the Northstar, the 2004-2005 GXP uses the Cadillac 4T80E. Owners in GM Forum's GXP section report the second most common GXP failure after head gaskets: an internal torque converter seal that shrinks or tears, producing a rumble-strip shudder at light throttle around 35-45 mph in 4th with the converter clutch applied, temporarily relieved by a light brake-pedal touch or cancelling overdrive. Left alone the converter clutch burns and the transmission starts slipping. The 4T80E input speed sensor is also a frequent failure that sets P0716/P0717 and forces limp mode; because it sits inside the case, it is normally replaced during the converter job. GM issued a bulletin on a 4T80E torque converter design change for 2005 DeVille and Bonneville.

The C190/R190 two-door AMG GT does not use a torque-converter automatic. It uses a rear-mounted Getrag/Magna 7DCL750 seven-speed dual-clutch transaxle — the same family as the Ford GT unit — and it is the single most expensive failure point on the car. Owner and specialist reports converge on a consistent set of failure modes: clutch pack wear producing shudder or hesitation on take-up, internal speed sensor failures throwing transmission control faults, oil weeping from the transaxle case weep holes, and seal/gasket leaks. Forum threads document malfunction codes tied to the electronic transmission control and DCT-specific CCP and SAP faults. The unit is intolerant of missed service: it demands strict fluid intervals and Mercedes-approved fluid, and abnormal vibration or slow engagement is the documented early warning that the gearbox is going. Because the transaxle sits at the rear of a torque tube, access is poor and labor is heavy. This is entirely distinct from the X290 four-door's front-mounted 9-speed AMG SPEEDSHIFT TCT.

Equinox models with the GM 6T70/6T75 six-speed automatic suffer shudder, harsh or delayed shifts, slipping, and loss of reverse. A common root cause is failure of the 3-5-reverse wave plate, which can crack and cause extreme shudder when reverse is engaged and eventual loss of drive. Overheated/degraded fluid that loses viscosity accelerates internal wear. Failures typically appear between roughly 60,000 and 150,000 miles. Owners report bucking when engaging gear, failure to shift out of 2nd, and inability to engage reverse.

The first-generation Enclave (built 2008-2017) uses the 6T70/6T75 6-speed automatic, whose stamped-steel 35R wave plate can crack at the teeth after enough shift cycles. When it fractures, the transmission abruptly loses 3rd, 5th, and reverse gears, and debris can damage the valve body, drums, and torque converter. GM's bulletin and special coverage for this failure cover 2008-2009 Enclaves.