P0734 on GMC
Gear 4 Incorrect Ratio
P0734 on GMC vehicles indicates gear 4 incorrect ratio. Au7o has documented this code across 1 GMC model — most commonly on Sierra 1500. This code means the Transmission/Powertrain Control Module detected an incorrect gear ratio in 4th gear. The module continuously compares input shaft speed to output shaft speed; if the ratio in 4th gear doesn't match the expected value, it sets P0734. This usually indicates the transmission is slipping or not fully engaging 4th gear due to a hydraulic, friction, or solenoid problem. Symptoms include slipping, flaring RPM, harsh or missed shifts, and possibly limp mode. Typical repair costs on GMC range from $1,800 to $3,500, depending on the specific model and root cause.
Common Causes of P0734
- •Low or degraded/burnt transmission fluid
- •Slipping clutch packs or worn friction elements in 4th gear
- •Stuck or faulty shift solenoid
- •Valve body / internal hydraulic leak or restriction
- •Worn or failing torque converter
- •Faulty input or output speed sensor
- •Internal mechanical wear (bands, planetary gears)
P0734 on GMC by Model
GMC Sierra 1500(1 issue)
- 4L60-E / 4L65-E Sun Shell Failure Causing Loss of Reverse and 2nd/4th Gear2000-2007
On GMT800 Sierra 1500 trucks equipped with the 4L60-E family automatic, a well-known internal failure is cracking or stripping of the reaction sun shell. Owners commonly report sudden loss of reverse, no 2nd gear, no 4th gear, or a truck that starts in 3rd gear after a bang or flare. This is widely documented in transmission rebuild literature, repair databases, and owner reports for GM trucks and SUVs using this transmission.
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What does P0734 mean on GMC?▼
P0734 stands for "Gear 4 Incorrect Ratio." This code means the Transmission/Powertrain Control Module detected an incorrect gear ratio in 4th gear. The module continuously compares input shaft speed to output shaft speed; if the ratio in 4th gear doesn't match the expected value, it sets P0734. This usually indicates the transmission is slipping or not fully engaging 4th gear due to a hydraulic, friction, or solenoid problem. Symptoms include slipping, flaring RPM, harsh or missed shifts, and possibly limp mode. On GMC specifically, this code is documented across 1 model.
What causes P0734 on GMC vehicles?▼
Common causes on GMC: Low or degraded/burnt transmission fluid, Slipping clutch packs or worn friction elements in 4th gear, Stuck or faulty shift solenoid, Valve body / internal hydraulic leak or restriction, Worn or failing torque converter. Specific causes vary by model and year — see the per-model sections below.
How much does it cost to fix P0734 on a GMC?▼
Repair costs on GMC range from $1,800 to $3,500, depending on the specific model and root cause.
Which GMC models have P0734 documented?▼
Au7o has documented P0734 on 1 GMC model: Sierra 1500.