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 advantages 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 compartment
- 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 compartment. 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 differential 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.

A manual transaxle uses a standard clutch and transmission. A foot-operated clutch engages and disengages the engine and transaxle. A hand-operated shift lever allows the operator to charge gear ratios. The basic parts relating to a manual transaxle are as follows:
- Transaxle Input Shaft—main shaft splined to the clutch disc turns the gear in the transaxle.
- Transaxle Input Gears—either freewheeling or fixed gears on the input shaft and meshes with the output gears.
- Transaxle Output Gears—either fixed or free- wheeling gears driven by the input gears.
- Transaxle Output Shaft—transfers torque to the ring gear, pinion gears, and differential.
- Transaxle Synchronizers—splined hub assemblies that can lock freewheeling gears to their shafts for engagement.
- Transaxle Differential—transfers gearbox torque to the driving axle and allows the axles to turn at different speeds.
- Transaxle Case—aluminum housing that encloses and supports parts of the transaxle.

The manual transaxle can be broken up into two separate units—a manual transaxle transmission and a transaxle differential.  A manual transaxle transmission provides several (usually four or five) forward gears and reverse. You will find that the names of shafts, gears, and other parts in the transaxle vary, depending on the location and function of the components. For example, the input shaft may also be called the main shaft, and the output shaft is called the pinion shaft because it drives the ring and pinion gear in the differential. The output, or pinion, shaft has a gear or sprocket for driving the differential ring gear.

The clutch used on the manual transaxle transmission is almost identical to the manual transmission clutch for rear-wheel drive vehicles. It uses a friction disc and spring-loaded pressure plate bolted to the flywheel. Some transaxles used a conventional clutch release mechanism (release bearing and fork); others use a long pushrod passing through the input shaft.

The transaxle differential, like a rear axle differential, transfers power to the axles and wheels while allowing one wheel to turn at a different speed than the other. A small pinion gear on the gearbox output shaft or countershaft turns the differential ring gear. The ring gear is fastened to the differential case. The case holds the spider gears (pinion gears and axle side gears) and a pinion shaft. The axle shafts are splined to the differential side gears.


 An automatic transaxle is a combination automatic transmission and differential combined into a single assembly. The basic parts of an automatic transaxle are as follows:
Transaxle Torque Converter—(fluid-type clutch that slips at low speed but locks up and transfers engine power at a predetermined speed; couples and uncouples engine crankshaft to transmission input shaft and gear train).
- Transaxle Oil Pump—(produces hydraulic pressure to operate, lubricate, and cool the automatic transaxle; its pressure activates the pistons and servos).
- Transaxle Valve Body—(controls the flow of the fluid to the pistons and servos in the transaxle; it contains hydraulic valves operated by the operators shift linkage and by engine speed and load-sensing components).
- Transaxle Pistons and Servos—(operates the clutches and bands when activated by fluid pressure from the valve body).
- Transaxle Clutches and Bands—(applies planetary gears in the transaxle; different bands and clutches are activated to operate different units in the gear-sets).
- Transaxle Planetary Gear sets—(provides different gear ratios and reverse in the automatic transaxle).
- Transaxle Differential—(transfers powers from the transmission components to the axle shafts).

Many of the components used in the automatic transaxle are also found in the automatic transmission. Operating principles of these components are the same as the automatic transmission. The differential of the automatic transaxle is similar to that used on the manual transaxle.

Q1. What is the purpose of the output shaft of a manual transaxle?
Q2.  In an automatic transaxle, what component(s) operate(s) the clutches and bands?