P0734 on Lincoln
Gear 4 Incorrect Ratio
P0734 on Lincoln vehicles indicates gear 4 incorrect ratio. Au7o has documented this code across 1 Lincoln model — most commonly on Aviator. 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 Lincoln range from $800 to $7,000, 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 Lincoln by Model
Lincoln Aviator(1 issue)
- 10R60/10R80 MHT Harsh/Delayed Shifts from Sticking Valve Body and CDF Clutch Sleeve Movement2020-2023
Many 2020-2023 Aviators with the 10R60 10-speed automatic (3.0L EcoBoost) and 10R80 MHT (Grand Touring PHEV) exhibit harsh 1-2/2-3 upshifts, clunky engagements into Drive or Reverse, and delayed shifts, with or without illuminated MIL. Root cause per Ford TSB 23-2250 is software/solenoid ID strategy, sticking valves in the main control valve body, and/or axial movement of the CDF clutch cylinder sleeve. Ford issued multiple TSBs (21-2316, 22-2102, 22-2428, 23-2250, 24-2046) and a related 10R80 class action is active in 2025 for sibling Ford/Lincoln models.
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What does P0734 mean on Lincoln?▼
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 Lincoln specifically, this code is documented across 1 model.
What causes P0734 on Lincoln vehicles?▼
Common causes on Lincoln: 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 Lincoln?▼
Repair costs on Lincoln range from $800 to $7,000, depending on the specific model and root cause.
Which Lincoln models have P0734 documented?▼
Au7o has documented P0734 on 1 Lincoln model: Aviator.