P0734 on Cadillac
Gear 4 Incorrect Ratio
P0734 on Cadillac vehicles indicates gear 4 incorrect ratio. Au7o has documented this code across 1 Cadillac model — most commonly on DeVille. 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 Cadillac range from $600 to $4,000, 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 Cadillac by Model
Cadillac DeVille(1 issue)
- 4T80-E Lower Valve Body and Fourth-Gear Clutch Failure Causes Slipping and Lost Overdrive1994-2005
The 4T80-E four-speed used behind the Northstar develops two documented and related faults. The lower control valve body and its channel plate/gasket leak internal pressure, producing 1-2 shift delays, slips and flares with P0731 or P0732, and slipping or complete loss of fourth gear with P0734. Where the pressure loss has been present for a while, the fourth-gear (overdrive) clutch pack cooks off its friction material - owners report finding the pan full of clutch debris and the fourth clutch stripped bare. The transmission fluid pressure switch assembly sets similar codes and is a cheaper first suspect. Owners also report the plastic locating ears on the valve body breaking. Fluid contaminated with clutch material is what carries the failure across the rest of the clutch packs, which is why a late fluid change on a slipping unit often makes it worse rather than better.
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What does P0734 mean on Cadillac?▼
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 Cadillac specifically, this code is documented across 1 model.
What causes P0734 on Cadillac vehicles?▼
Common causes on Cadillac: 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 Cadillac?▼
Repair costs on Cadillac range from $600 to $4,000, depending on the specific model and root cause.
Which Cadillac models have P0734 documented?▼
Au7o has documented P0734 on 1 Cadillac model: DeVille.