45625-3B620
KINGMAY
45625-3B620
Hyundai, Kia
Tucson, Sonata
2021, 2020, 2019, 2018, 2017, 2016, 2015, 2014, 2013, 2012, 2011
| Quantity: | |
|---|---|
Product Description
The Underdrive Brake Disk Set 45625-3B620 is a high-quality automatic transmission internal clutch component designed for Hyundai and Kia vehicles equipped with A6MF series automatic transmissions. It works as a key friction control component inside the transmission system, helping control the engagement and release of the underdrive gear clutch during gear shifting.
The 45625-3B620 Underdrive Brake Disk Set is an internal automatic transmission friction and steel plate assembly designed for selected Hyundai and Kia 6-speed automatic transmissions. Its official Hyundai catalog description is Disk Set – Under Drive Brake, while Kia also identifies the component as a Transmission Clutch Friction Plate / Underdrive Brake Set, including both friction and steel plates.
Installed inside the transmission, this multi-plate brake pack works together with the underdrive brake hub, piston, hydraulic control system, and other clutch/brake elements. When hydraulic pressure is applied, the friction plates and steel plates are compressed together to control the rotation of the related transmission member. This allows the gearbox to establish the required internal torque path and achieve smooth, controlled gear engagement.
The 45625-3B620 is therefore not a wheel brake rotor or conventional brake disc. It is a precision internal transmission component used in the automatic transmission clutch/brake system.
| Specification | Data |
|---|---|
| OE / OEM Part Number | 45625-3B620 |
| Official Hyundai Name | Disk Set – Under Drive Brake |
| Kia Description | Transmission Clutch Friction Plate / Underdrive Brake Set |
| Hyundai Part Code | 45625G |
| Product Type | Automatic Transmission Underdrive Brake Disk Set |
| Component Category | Automatic Transmission Internal Parts |
| Set Composition | 3 Steel Discs + 1 Pressure Plate + 3 Friction Discs |
| Total Main Plates | 7 Pieces |
| Steel Disc Thickness | 1.8 mm × 3 |
| Pressure Plate Thickness | 2.5 mm × 1 |
| Friction Disc Thickness | 1.75 mm × 3 |
| Catalog Item Weight | 0.40 lb / approx. 0.18 kg |
| Installation Type | Direct Replacement |
| Transmission Family | A6MF-series applications |
| Reported Compatible Transmissions | A6MF1, A6MF2, A6MF3, A6MF2H, A6MF2H-1, A6MF2H-2 |
| Condition | New replacement component |
Hyundai's parts catalog lists the item weight as 0.40 lb (approximately 0.18 kg). Transmission-parts technical data for 45625-3B620 specifies a pack consisting of three 1.8 mm steel discs, one 2.5 mm pressure plate, and three 1.75 mm friction discs.
Important: Public Hyundai/Kia catalog sources do not provide a verified overall outside diameter or inside diameter specifically for 45625-3B620. Therefore, unverified dimensions from similar part numbers such as 45625-3B601 should not be presented as official 45625-3B620 specifications.
The set uses alternating friction and steel plates to create the required friction interface inside the automatic transmission. The multi-disc structure provides a compact way to transmit and control substantial torque inside the gearbox.
The 45625-3B620 set includes both friction and steel elements rather than being a single transmission plate. Kia's parts description specifically identifies it as an Underdrive Brake set containing frictions and steels.
The friction discs provide the friction surface required during hydraulic engagement, while the steel plates provide the corresponding reaction surfaces. Correct plate thickness and clutch-pack clearance are important for stable engagement and release.
Technical transmission-parts catalogs associate 45625-3B620 with Hyundai/Kia A6MF-family transmissions, including A6MF1 and A6MF2-series applications.
The Hyundai OEM catalog identifies 45625-3B620 as a direct replacement component. Correct installation still requires confirmation of the transmission code and vehicle VIN before ordering.
The main function of the 45625-3B620 Underdrive Brake Disk Set is to provide a controlled holding and friction element inside the automatic transmission.
Automatic transmissions use several clutch and brake packs to control different members of the planetary gear system. The transmission control system directs hydraulic pressure to the appropriate clutch or brake piston. When pressure is applied to the underdrive brake assembly, the piston compresses the friction and steel plates together.
The resulting friction locks or controls the corresponding transmission member, helping the gearbox establish the required gear ratio and transmit engine torque to the wheels.
A technical A6MF1 clutch-and-brake application chart shows the U/D Brake as one of the primary hydraulically operated transmission elements used during forward gear operation.
The Underdrive Brake Disk Set plays several important roles inside the transmission:
Gear Ratio Control:
It works with the planetary gear system and other clutch/brake packs to establish the correct transmission ratio.
Torque Transfer:
When the friction and steel plates are compressed, they provide the frictional holding force required for controlled torque transmission.
Smooth Gear Engagement:
Correct friction characteristics and plate clearance help the transmission engage gears progressively instead of producing excessive shock.
Transmission Stability:
By correctly holding the required internal rotating member, the underdrive brake pack contributes to stable operation during acceleration and gear changes.
Protection of Related Components:
A properly functioning friction pack reduces uncontrolled clutch slip and excessive heat that could otherwise damage the drum, hub, piston, seals, transmission fluid, and neighboring clutch assemblies.
Hyundai's parts catalog lists 45625-3B620 for applications including:
| Vehicle | Cataloged Years |
|---|---|
| Hyundai Elantra GT | 2013–2014 |
| Hyundai Sonata | 2015–2019 |
| Hyundai Sonata Hybrid | 2011–2015* |
| Hyundai Tucson | 2014–2021 |
Possible symptoms:
Transmission slipping
Engine RPM increases without proportional vehicle acceleration
Delayed engagement
Abnormal shifting between gears
Poor acceleration under load
Possible cause:
Repeated engagement gradually wears the friction material. Excessive heat, contaminated transmission fluid, insufficient hydraulic pressure, or prolonged clutch slip can accelerate wear.
Solution:
Remove and inspect the underdrive brake pack. Replace friction and steel plates when the friction lining is worn, damaged, overheated, or outside service specifications. The related piston, seals, hub, and drum should also be inspected before installing the replacement pack.
Possible symptoms:
Harsh or unstable shifts
Transmission slipping after warming up
Burnt smell from transmission fluid
Dark or contaminated ATF
Reduced holding capacity
Possible cause:
When the brake pack slips instead of locking correctly, friction generates excessive heat. This can glaze or burn the friction material and discolor the steel plates.
Solution:
Replace damaged friction and steel plates and diagnose the reason for overheating before reassembly. Check hydraulic pressure, transmission fluid condition, valve body operation, solenoids, pistons, and sealing components. Simply replacing the discs without correcting the hydraulic problem may cause the new pack to fail again.
Possible symptoms:
Harsh engagement
Uneven clutch application
Transmission drag
Poor release after shifting
Repeated friction plate wear
Possible cause:
Extreme transmission temperature can distort the steel reaction plates.
Solution:
Inspect each steel plate for heat spots, discoloration, distortion, and surface damage. Replace the complete affected plate set when necessary and check clutch-pack clearance during assembly.
Possible symptoms:
Delayed gear engagement
Excessive clutch slip
Harsh gear engagement
Transmission drag
Rapid friction material wear
Possible cause:
Incorrect plate thickness, excessive wear, incorrect assembly order, or inappropriate replacement components can change the working clearance of the brake pack.
Solution:
Use the correct plate specification for the transmission version and measure clutch clearance according to the applicable transmission repair procedure before final assembly.
For 45625-3B620, published technical data identifies 3 × 1.8 mm steel discs, 1 × 2.5 mm pressure plate and 3 × 1.75 mm friction discs.
Possible symptoms:
Underdrive brake slipping even with new friction plates
Delayed engagement
Incorrect gear ratio
Intermittent transmission slipping
Harsh or inconsistent shifting
Possible causes:
The problem may originate outside the friction pack, including:
Worn piston seals
Hydraulic leakage
Valve-body wear
Solenoid malfunction
Low or incorrect transmission fluid
Oil pump or pressure-control problems
Solution:
Perform hydraulic-pressure and electronic diagnosis before assuming that the friction plates alone are responsible. A6MF technical information confirms that the U/D brake is hydraulically controlled, so inadequate apply pressure can prevent the pack from holding correctly.
A severely worn or slipping internal clutch/brake pack can cause the transmission input and output speeds to differ from the ratio expected by the TCM. This may result in incorrect-ratio symptoms or transmission fault codes.
The correct repair procedure is to diagnose the complete system first, including:
Transmission fault codes
Input and output speed sensors
Solenoid operation
Hydraulic pressure
ATF condition
Valve body
Underdrive brake pack
Low/Reverse and other related clutch packs
The Underdrive Brake Disk Set should not automatically be replaced solely because an incorrect-ratio fault code is present.
The 45625-3B620 is located inside the automatic transmission and is not normally an external bolt-on service part. Transmission disassembly is required for replacement.
For professional repair:
Confirm the OE number, VIN and transmission model.
Drain and inspect the transmission fluid.
Remove and disassemble the transmission according to the service procedure.
Inspect the underdrive brake friction plates, steel plates, pressure plate, hub, drum, piston and seals.
Check for burnt friction material or metal debris.
Replace damaged components.
Measure clutch-pack clearance.
Inspect the valve body and hydraulic system when abnormal wear is present.
Refill with the transmission fluid specified for the vehicle.
Perform the appropriate transmission/TCM learning procedure when required after repair.
Technical service information for the A6MF family notes that transmission learning is used to compensate for factors such as hydraulic pressure, clutch clearances and wear, and may be required following relevant transmission repairs.
Although the same 45625-3B620 part number appears across several Hyundai/Kia applications, transmission components can change according to:
Vehicle model
Model year
Production date
Engine
2WD / AWD configuration
Transmission code
VIN
Always verify OE number 45625-3B620 against the vehicle VIN and transmission identification code before ordering. Similar numbers such as 45625-3B601, 45625-3B610 and 45625-3B620 should not automatically be treated as interchangeable without confirming the specific transmission configuration.
