ATST provides structured step-by-step methods. Instead of random testing, you follow a clear logic to identify the real cause more quickly.

Yes. One diagnostic error or unnecessary replacement can be expensive. ATST helps secure interventions and reduce time spent per vehicle.

Automatic transmission specialists with real workshop diagnostic and repair experience. Contact us

Yes. ATST supports technicians on concrete cases when a diagnosis or repair is blocked. Contact us

Detailed technical manuals by model, video guides, diagnostic procedures, real case feedback and training videos.

Yes. Content is continuously updated with new cases, corrections and field feedback.

Yes. The goal is to confirm the diagnosis before heavy repair or full replacement to avoid unnecessary costs.

Diagnosing an automatic transmission failure requires several steps: checking the fluid level and condition, performing a test drive to identify symptoms (jerking, noise, power loss), reading error codes with a diagnostic tool, and visual inspection of components. Our detailed diagnostic guides walk you through each step to quickly identify the root cause of the problem.

The cost of an automatic transmission repair varies considerably depending on the nature of the fault and the vehicle model. A simple fluid change can cost between 100 and 300 euros, while a torque converter repair can reach 1,000 to 2,000 euros. A complete overhaul or replacement can cost between 2,000 and 5,000 euros. Our resources help you accurately identify the fault to avoid unnecessary repairs and optimize costs.

Common symptoms include: jerking or jolting during gear changes, abnormal noises (grinding, clunking), power loss or difficulty accelerating, fluid leaks, engine warning light on, burning smell, and difficulty shifting certain gears. If you notice these symptoms, it is important to have your vehicle diagnosed quickly to prevent further damage.

The type of fluid depends on the model and brand of your automatic transmission. Each manufacturer specifies a particular fluid type (for example, ATF for some brands, or specific fluids like Dexron, Mercon, etc.). It is crucial to use the manufacturer-recommended fluid, as an unsuitable fluid can seriously damage the transmission. Our technical manuals detail the exact specifications for each model.

Service frequency varies by manufacturer and driving conditions. Generally, a fluid change is recommended every 60,000 to 100,000 kilometres for modern automatic transmissions, or every 2 to 3 years. For vehicles used intensively (towing, city driving), more frequent service (every 40,000 km) may be necessary. Consult your vehicle manual or our guides for recommendations specific to your model.

Some simple operations like fluid changes can be performed by experienced amateurs, but most repairs require specialized tools, in-depth technical knowledge and a suitable working environment. Complex repairs (valve body, torque converter, solenoids) should be entrusted to professionals. Our resources guide you through operations you can do yourself and help you identify when to call a professional.

Error codes are accessible via an OBD-II diagnostic tool. Each code corresponds to a specific problem (for example, P0700 indicates a general transmission problem). Our diagnostic guides include a comprehensive database of error codes with their meaning and recommended corrective actions, allowing you to quickly identify the source of the problem.

An automatic transmission that slips indicates excessive clutch or torque converter slippage. Main causes: low or degraded fluid, worn clutches, faulty torque converter, failed solenoids, or inadequate line pressure. Solutions: check fluid level and colour (dark brown or burnt smell = urgent change), test line pressure, inspect solenoids and clutches. ZF 6HP and Aisin units are particularly sensitive to fluid quality. ATST provides diagnostic trees by model to pinpoint the exact cause.

Limp mode is a protection activated by the TCM when it detects an abnormality. The vehicle usually remains in 3rd or 4th gear. Common causes: faulty speed sensors, defective solenoids, low fluid level, worn valve body, or electrical fault. First step: read OBD-II codes (P0700, P0715, P0720, etc.) to identify the source. A fluid change and filter replacement may suffice if the fluid is contaminated. For complex repairs, ATST offers case-by-case diagnostic support.

Shuddering or vibration when hot often indicates a problem linked to thermal expansion or fluid degradation. Typical causes: faulty torque converter (shudder), clutches slipping when hot, oxidised fluid losing its properties, or solenoids reacting poorly to heat. Common on ZF 5HP19, 6HP and Aisin units. Procedure: test drive when cold then hot, check fluid colour and smell, test torque converter lock-up. A fluid change with the correct specification can resolve the issue if the fluid is degraded. ATST manuals detail test procedures by model.

A clunk when shifting indicates harsh clutch or brake engagement. Causes: incorrect pressure adjustment, worn clutches or brake bands, excessive play in planetary gears, or faulty engine/transmission mount. DSG (DQ250, DQ381) and Powershift units can produce characteristic clunks with faulty synchronisation. Diagnosis: identify which shifts (1-2, 2-3, etc.) produce the clunk, check mounts, test line pressure. ATST provides diagnostic guides by transmission type.

A transmission is considered end-of-life when no economical repair is possible. Signs: no movement in D or R (despite correct fluid), severe metallic noise, metal debris in the fluid, total pressure loss. Before concluding: check fluid level, torque converter, and electrical controls (TCM, sensors). An electrical fault or torque converter can simulate a dead transmission. Replacement cost: €2,500 to €6,000 depending on vehicle. ATST recommends a structured diagnostic to avoid unnecessary replacement.

Being stuck in one or more gears can have electrical, hydraulic or mechanical causes. Common causes: faulty output/input speed sensor, stuck shift solenoid, clogged valve body, or seized clutch. On dual-clutch units (DSG, DCT), a faulty mechatronic module is often the cause. Diagnosis: read codes P0720, P0715, etc., check line pressure and solenoid operation. An adaptive reset may temporarily correct the issue. ATST resources include test procedures by fault code.

A transmission light (often with the check engine light) requires immediate code reading. Do not ignore: driving in degraded mode can worsen damage. Steps: 1) Connect OBD-II tool and note codes (P0700 series). 2) Check fluid level. 3) Avoid aggressive driving or towing in drive if possible. 4) Consult a diagnostic guide for the specific code. Codes P0740, P0750, P0760 indicate solenoid faults. ATST offers a code database with corrective actions by model.

A whine often indicates the oil pump (wear, cavitation) or a level problem. Grinding can come from bearings, planetary gears, or the torque converter. Location: whine at idle = often pump; when shifting = clutches or hydraulic. Check fluid level immediately. A failing pump causes pressure loss and damages the transmission. ZF 6HP units have pumps sensitive to contamination. ATST recommends prompt inspection and provides pump test procedures by model.

Gravity drain (plug drain) replaces only about 40–50% of the fluid; the torque converter and lines retain the old fluid. Flush (machine) renews 90% or more but risks dislodging deposits on heavily contaminated units. Recommendation: for never-serviced transmissions or > 150,000 km, prefer a gravity drain then a second one 5,000 km later. Sealed units (no dipstick) require specific equipment. ATST details procedures by model (ZF, Aisin, Mercedes 722.6, etc.).

No, do not mix fluids of different specifications. Each fluid (Dexron, Mercon, ATF+4, ZF LifeGuard, etc.) has its own additives and chemistry. Mixing can cause slipping, overheating and internal damage. For emergency top-up: use only the exact same specification (check manual or bottle label). For fluid type conversion: complete drain and flush per manufacturer procedure. ATST specifies the exact fluid for each model in its technical manuals.

So-called 'lifetime sealed' units (some ZF 8HP, Honda, Nissan CVT) are designed not to be user-serviced. In practice, a fluid change remains beneficial at 80,000 to 100,000 km to extend life. Risk: on very worn units, new fluid can change clutch behaviour and reveal hidden issues. Procedure: use the correct equipment (temperature, level) and specification. ATST provides procedures for the most common sealed transmissions.

The procedure varies by model. Units with dipstick: warm engine, idle, selector in P, level ground. Pull dipstick, wipe, reinsert, read level between marks. Units without dipstick (sealed): require level check via fill plug or a procedure at a specific temperature (often 35–45°C). Common errors: checking when cold (false reading), engine off (level too high). Dark brown fluid or burnt smell signals urgent change. ATST manuals specify the exact procedure by model.

ZF 6HP26 and 6HP28 (BMW, Audi, Jaguar, Land Rover) have recurring faults: faulty EDS solenoids (jerking, limp mode), worn turbine seals (hot shudder), worn clutch packs, and valve body issues. Common codes: P0741, P1741, P0780. Fluid quality (ZF LifeGuard 6 or equivalent) is critical; wrong fluid accelerates failures. Typical repair: solenoid pack replacement, turbine seals, or valve body overhaul. ATST provides detailed 6HP guides with diagnostic trees and disassembly procedures.

Aisin units (Toyota, Lexus, Volvo, VW) such as U660, U760, AWF21, A960E have known weak points: faulty SLT/SLTU solenoids, worn C1/C2 clutches, and on Aisin CVTs, chain and variator wear. Symptoms: jerk on take-off, delayed engagement, whining noise (CVT). Common codes: P2714, P0776. Toyota WS or equivalent fluid is mandatory. ATST covers diagnostic and repair procedures for the most common Aisin units in Europe.

DSG DQ250 (6-speed, wet) and DQ381 (7-speed, wet) suffer from: worn clutches (jerking, smell), faulty mechatronic module (electrohydraulic faults), speed sensors, and overheating under sporty driving. Typical codes: P0841, P17BF, P189C. DSG fluid change every 60,000 km is essential. An adaptive 'recalibration' via diagnostics may temporarily improve behaviour. Mechatronic module repair or clutch replacement are the most common interventions. ATST provides DSG-specific procedures.

CVTs (Jatco, Aisin, Honda) have vulnerabilities: worn chain or push belt (whining, slipping), overheating (no dedicated cooler), and oil pump. Symptoms: whining noise on acceleration, shuddering, 'false gear shifts'. CVT-specific fluid is critical; standard ATF will destroy the unit. Fluid change recommended every 60,000 to 90,000 km. Nissan CVTs (Jatco) are particularly sensitive. Repair is often costly (variator/pulley replacement). ATST provides diagnostic guides for common European CVTs.

The choice depends on repair cost versus used or remanufactured unit cost, and overall vehicle condition. Repair if: localised fault (solenoids, valve body, torque converter) and reasonable mileage (< 200,000 km). Replace if: general wear, major internal damage, or repair cost > 70% of remanufactured unit price. A remanufactured unit costs €1,500 to €4,000 fitted. Always confirm diagnosis before deciding: ATST recommends a structured diagnostic to avoid unnecessary replacement or repair.

A well-maintained automatic transmission can last 200,000 to 300,000 km. Key factors: regular fluid changes (every 60,000 to 100,000 km depending on model), correct fluid specification, and appropriate driving (avoid harsh launches, excessive towing). ZF 6HP, DSG and CVT units are more maintenance-sensitive. A never-serviced transmission may fail by 120,000 km. ATST recommends following manufacturer intervals and provides maintenance guides by model to maximise lifespan.