We will explore the operating principles of electronically controlled Aisin 6-speed automatic transmission system designed for VW
We will explore the operating principles of electronically controlled Aisin 6-speed automatic transmission system designed for VW.
CONSTRUCTION & OPERATION
This automatic transmission is based on the Lepelletier arrangement, is a simple planet in front of a Ravigneaux arrangement, which allows six forward speeds, neutral and reverse, using five shifting elements.
Gears consist of three multi-disc coupling, two multiple disc brakes and a free-wheel. The gears are switched on/off using the electromechanic-hydraulic control unit positioned in the control valve assembly. Other components include sun gears, planetary gears, planet carrier, torque converter (starter ring gear welded on), ATF pump and ATF heat exchanger.
Additional components include;
• Transmission Control Module(TCM)
• Shift control switch
• Valve block
• Transmission range (TR) switch
• Vehicle speed sensor
• Input shaft speed sensor
• Fluid temperature sensor
• Shift warning lamps
Transmission selection is done by the gearstick, comprising of Park(P), Reverse(R), Neutral(N), Drive(D) and Sport(S) modes. To move vehicle from P the ignition must be on and the foot brake pressed. also the locking button on the stick must be pressed. For reverse the locking button must be engaged. If the N position has been engaged for a long time the foot brake must be applied in to leave this position.
The TCM starts the switching of the gears and monitors for any problems. It uses sensors to activate actuators to allow for gear change. This is done by using solenoids to control fluid within the valve block, which allows for the appropriate clutch pack to shift gears depending on what is required. The torque converter serves as starting element and when vehicle started the ATF pump quickly fills and pressurises it. This pressurisation is needed to order to produce the force necessary to shift gears. ATF heat exchanger cools down ATF fluid as temperature in the converter can rise beyond operating range under load.
TYPICAL FAULT
FAULT SYMPTOM SYMPTOM CAUSE
U0101- Lost communication with TCM, meaning TCM and other modules not talking to each other. Car stuck in gear
No power and unable to be driven
Illuminated check engine light
Limp mode Dead Battery
Faulty TCM (rarely)
TCM is open or shorted
TCM circuit has poor electrical connection
Open in CAN bus (+ or -) circuit
Short (power or ground) in CAN bus circuit
