P1740 on Ford: How to Diagnose & Fix
Torque Converter Clutch System Fault (Manufacturer Specific)
1 Ford model · 1 documented issue · 1 critical · $1,800-$3,500 repair
P1740 on Ford by model: symptoms, diagnosis and fix
The 4R70W (and later 4R75W/4R75E) 4-speed automatic behind the 4.2L V6 and 4.6L/5.4L V8s is prone to several high-mileage failures: a broken reverse (cast) band that produces a loud POP and loss of reverse; a cracked forward-clutch drum snap-ring groove on 2005+ units causing loss of ALL forward gears while reverse still works; worn overdrive band and clutches causing slipping; and solenoid-body/servo wear causing harsh or erratic shifts. Failures accelerate under towing/heavy loads and when fluid changes are neglected.
Common Symptoms
- No reverse engagement or a loud pop then loss of reverse
- Truck has reverse but no forward movement (2005+ forward-drum failure)
- Slipping or flaring on 1-2/2-3 upshifts
- Delayed or harsh engagement into Drive
- Overdrive slipping under load
- Limp mode (stuck in one gear)
How to Fix
Diagnose fluid condition (burnt smell, metal), line pressure, and DTCs before teardown. Repair typically means a full rebuild with upgraded forward drum/snap ring, new bands, updated solenoid pack, and torque converter; add an auxiliary transmission cooler if the truck tows. Regular fluid/filter service (Mercon V) is the main preventive measure.
What you need to fix it
Only diagnosis- and fitment-reviewed repair parts are linked here.
- Forward clutch drum (upgraded, forged) — Sonnax Smart-TechCross-refSonnax 76654-01K, TCS Smart-Tech 76654-01K, Sonnax 76655-01K (high-capacity kit version)$250–$300
This is the fix for the 2005+ failure mode described in the issue: the OE stamped drum cracks at the snap-ring groove and the truck loses ALL forward gears while reverse still works. The Sonnax replacement is one-piece forged with a deep…
- Auxiliary transmission oil cooler (tow duty)Cross-refTru-Cool Max LPD4739 (40,000 GVW, low pressure drop, thermal, Tru-Cool LPD47391 / OC-4739-1, Hayden / Derale stacked-plate equivalents$100–$165
Universal-fit add-on, not a year- or engine-specific part — this is the 'add an auxiliary cooler if the truck tows' half of the documented fix, and the cheapest insurance against a repeat failure.
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Sources for this issue (1)
P1740 code reference
General diagnostic-code context. The code alone does not confirm a cause for your vehicle; use the applicable issue card and its sources.
Frequently asked questions
What does P1740 mean on a Ford?
P1740 stands for "Torque Converter Clutch System Fault (Manufacturer Specific)." This is a manufacturer-specific transmission code indicating a fault in the torque converter clutch (TCC) system. The torque converter clutch mechanically locks the engine to the transmission at cruising speeds to reduce slippage and improve fuel economy; the computer controls it with a solenoid and monitors whether it locks and unlocks correctly. This code sets when the system doesn't behave as expected — for example, the clutch fails to lock, slips, or the control circuit is faulty. Symptoms can include shudder, poor fuel economy, higher RPM at cruise, or a transmission that won't lock up. On Ford it is documented across 1 model: F-150.
What are the most common causes of P1740?
The most common causes of P1740 are: Faulty torque converter clutch (TCC) solenoid, Worn or failing torque converter, Low, dirty, or contaminated transmission fluid, Valve body wear or stuck valve, Damaged TCC solenoid wiring/connector, Internal hydraulic pressure loss, Faulty transmission control module (TCM). The specific cause varies by vehicle.
How much does it cost to fix P1740 on a Ford?
Published repair estimates on Ford range from $1,800 to $3,500 depending on the model and root cause. If an issue mentions a recall or campaign, check your VIN with the manufacturer or NHTSA and confirm eligibility and coverage with a dealer.
Looking for P1740 on a different make?
View P1740 across all makes →Content compiled with AI assistance using NHTSA complaints, TSBs, and owner reports. May contain errors. Always verify with your vehicle's service manual.