9.8 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 vehicle has several advantages over a vehicle with rear-wheel drive. A few of these advantages are the following:

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.

Manual Transaxles

A manual transaxle uses a standard clutch and transmission (Figure 9-28). 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 the following:


Figure 9-28 — Manual 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 use 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.

Automatic Transaxles

An automatic transaxle is a combination automatic transmission and differential combined into a single assembly (Figure 9-29). The basic parts of an automatic transaxle are as follows:


Figure 9-29 — Automatic transaxle.

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 those of the automatic transmission. The differential of the automatic transaxle is similar to that used on the manual transaxle.

Summary

In this chapter, you were introduced to automotive clutches, transmissions and transaxles. You learned how the manual and automatic transmission operates and provides power to the drive wheels of the vehicle. In addition you learned the differences between a transmission and a transaxle. The power flow to the drive wheels is something a construction mechanic needs to understand to enable them to properly troubleshoot and diagnose equipment. When you have mastered the knowledge of these systems you will become a better CM.