The Volkswagen rear axle and transaxle are combined in a single unit. Therefore, some of the possible problems may be hard to attribute to one assembly or the other, especially in the event of lubricant leakage. When lubricant leaks from one part of the unit, it may be blown onto another section or carried there by gravity while the car is in motion. However, like the transaxle, the Volkswagen rear axle is a very sturdy piece of equipment, and not likely to give any trouble for a very long time. In the event of trouble, here are possible problems and causes:REAR AXLE LEAKS LUBRICANT
REAR AXLE NOISES
Because of the close proximity of the rear axle to the transaxle and the engine, it should be ascertained that the rear axle is in fact making whatever noise is being heard. The following are possible causes of noise in the vicinity of the rear axle:
Tire noise-driving the car over various types of road surfaces will reveal the extent of tire noise. If tire noise is to be minimized for noise detection purposes, it is advisable to drive on a smooth asphalt or black top road while trying to pinpoint noise causes.
Rear wheel bearing noise can be checked by jacking up the car and rotating the rear wheels, by coasting at a low speed, or by driving at low speed and applying the brakes after disengaging the clutch. If, in the latter test, the noise diminishes, defective wheel bearings are a definite possibility.
Noise when accelerating in a straight line is generally caused by heavy heel contact on the gear teeth. It is necessary to move the ring gear nearer to the drive pinion.
If noise is most evident when coasting with the car in gear and the throttle closed, it is most likely that there is heavy toe contact on the gear teeth, in which case the ring gear must be moved away from the drive pinion.
The toe end of the gear tooth is the smaller of the two circles formed by the ends of the gear teeth, while the heel is the larger circle.
If the noise is present only when the car is driven around a curve, the cause of the noise is probably excessive backlash between gears, damaged gears or thrust washers, differential side gears that are tight in the case, or differential-pinion gears that are tight on the pinion shaft.
The cause of a knocking noise in the rear axle may be bearings or gears that are either damaged or badly worn.
The presence of a constant humming noise may indicate that the drive pinion or ring gear is out of adjustment. Such a condition should be remedied before gear-tooth wear becomes significant and the noise changes from a hum to a growl.
Excessive end-play in the shafts of the rear axles will result in a thumping sound being heard when the car is driven around a corner on a rough road.