Refilling the Transmission

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Automatic transmission service

Construction Mechanic Basic Volume 2

Manual Transaxle

Refilling the Transmission
Reinstall the transmission oil pan, the oil plug, and the fill tube. Fill the transmission with the fluid prescribed by the manufacturer to the proper level. With the brakes applied, start the engine and let it idle for a couple of minutes. Move the gear selector through all gear ranges several times, allowing the fluid to flow through the entire hydraulic system to release any trapped air. Return the selector lever to park or neutral and recheck the fluid level. Bring the fluid to the proper level. Run the vehicle until operating temperature is reached, checking for leaks. Also, recheck the fluid and adjust the level as necessary.

CAUTION
Overfilling an automatic transmission will cause foaming of the fluid. This condition prevents the internal working parts from being properly lubricated, causing slow actuation of the clutches and bands. Eventual burning of the clutches and bands results. DO NOT OVER-FILL AN AUTOMATIC TRANSMISSION.

TRANSAXLES
Learning Objective: Identify components of the manual and automatic transaxles. State the differences between transmissions and transaxles.

A transaxle is a transmission and differential combination in a single assembly. Transaxles are used in front-wheel drive vehicles. A transaxle allows the wheels next to the engine to propel the vehicle. Short drive axles are used to connect the transaxle output to the hubs and drive wheels.

Vehicle manufacturers claim that a transaxle and front-wheel drive has several advantages over a vehicle with rear-wheel drive. A few of these advan-tages are the following:

Improved efficiency and reduced drive train weight

Improved traction on slippery surfaces because of increased weight on the drive wheels

Increased passenger compartment space (no hump in floorboard for rear drive shaft)

Less unsprung weight (weight that must move with suspension action), thereby providing a smoother ride

Quieter operation since engine and drive train noise is centrally located in the engine com-partment

Improved safety because of the increased mass in front of the passengers

Most transaxles are designed so that the engine can be transverse (sideways) mounted in the engine com-partment.
The transaxle bolts to the rear of the engine.
This produces a very compact unit. Engine torque enters the transaxle transmission. The transmission transfers power to the differential. Then the differ-ential turns the drive axles that rotate the front wheels.

Both manual and automatic transaxles are available. Manual transaxle uses a friction clutch and a standard transmission-type gearbox. An automatic transaxle uses a torque converter and a hydraulic system to control gear engagement.