Understanding Car Transmission Systems: A Comprehensive Guide
Car Transmission Systems
Epicyclic Train
This system builds speed transmission relationships, offering several transmission ratios and reverse spin. Key components include the planetary gear and ring gear. Some systems use two epicyclic trains, uniting a planetary gear with other fitted pieces.
Brakes and Clutches
Cinta Brake
The drum rotates while a band tightens when the piston receives pressure, activating the brake.
Disc Brake
Oil pushes the piston, compressing discs of different materials. The housing is oil-cooled.
Disc Clutch
Joins two pieces to transmit torque when operated.
Freewheel
Functions like a bicycle wheel, allowing one direction to drive and the other to spin freely.
Parking Mechanism
Blocks the shaft when the lever is in “P”, ensuring the vehicle remains stationary.
Oil System
Circulates oil, with converters located near the gearbox entrance.
Valves
Control the hydraulic system.
Sensors
Send vehicle operation information to a central processing unit.
Electronic Control
Interprets sensor data and controls solenoids.
Semi-Automatic Transmission
Commonly used in tractors, this system offers forward, backward, and neutral positions.
Drives
Two pulleys connect to the engine via a clutch disc. A belt or chain rotates the pulleys. This system is often used in smaller vehicles and motorcycles.
DSG (Direct-Shift Gearbox)
An automatic transmission with two gearboxes in a single block. Two gears are always engaged, and an intelligent mechatronic system controls gear changes.
Reducer
Modifies output revolutions for optimal performance. It consists of two interlocking gears: a crown and a pinion.
- Helical pinion and crown: For front-wheel drive vehicles.
- Bevel pinion and crown: For rear-wheel or front-wheel drive vehicles with longitudinal engines.
- Double-conical reduction: For industrial vehicles.
Differential
Distributes torque to the wheels, allowing for speed differences during turns.
Crown and Pinion Adjustment
Nuts and washers adjust the clearance between pinion and crown (0.05 to 0.15mm). Over-tightening should be avoided.
Noise Check
With hot oil and the car in neutral, accelerate the engine. If the noise disappears when shifting out of neutral, the gears are the source. If it persists, the pinion bearings are likely the cause.
4×4 Systems
Manual 4×4
Offers more torque but has more parts and less power. The front axle can be engaged when needed via a transfer case. Total traction is typically used only at low speeds.
Automatic 4×4
Provides traction on either the front or rear axle (depending on the vehicle type). Systems like “Haldex” or “x-drive” engage the other axle when a difference in rotation is detected.
Haldex
A system that proportionally distributes torque. It combines mechanical, hydraulic, and electronic components. The hydraulic circuit controls mechanical parts, while the electronic system manages the coupling and monitors the axles via sensors, enhancing safety.
Integral 4×4
Offers continuous traction and requires a central differential for turning. A potential drawback is the lack of a locking system; if a wheel loses grip, torque is lost. Solutions include limited-slip differentials or Torsen differentials.
Transmission Components
Transmission Shafts
Steel bars transmit torque from the gearbox to the front or rear. Universal joints connect shafts when necessary.
Axle Shafts
Transmit torque from the differential to the wheels. Constant velocity joints allow for steering. Proper lubrication is essential.
Faults
- Worn components
- Lack of lubrication in the transfer case
- Haldex circuit issues
- Damaged axle shafts and bearings
Maintenance
: SAE 75W90 oil-transfer, “Haldex oil and filter change 60 000 km, spider-trees and semi-oiled, bellows without cracks and grease balls.