How to Troubleshoot a Front Axle Transmission

Written by chris stevenson
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How to Troubleshoot a Front Axle Transmission
Every vehicle owner should be aware of the symptoms from a failing front axle transmission. (old gearbox dumped in a rest area on the side of the road image by Undy from Fotolia.com)

The front axle transmission has the responsibility of transferring the engine's power through a system of gears to the front drive wheels. Also called the transaxle, this component consists of the inner transmission housing and gears and the CV (constant velocity joint), which has been called the "outward" transmission drive. Both units function as one and are susceptible to various problems. Vehicle owners should be aware of certain symptoms that the transaxle can relay before the problem becomes too serious, leading to a transaxle that does not shift or move the car at all.

Skill level:
Moderate

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Things you need

  • Floor jack
  • Jack stands
  • Rags
  • Tire iron
  • Torque wrench
  • Owner's manual
  • Notebook and pen

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Instructions

  1. 1

    Place the vehicle in park or neutral with the emergency brake set. Raise the hood. With the engine running, check the transaxle dipstick level. The transmission fluid level should be at the top mark. The fluid condition should appear a clean, translucent red, with no burnt odour or discolouration. Black or brown fluid indicates contaminants and means that you should change the fluid and the filter. A low fluid level can cause excessive slippage in the gears during acceleration or while shifting.

  2. 2

    Take the vehicle for a drive and listen carefully for any noises originating from the front end in the vicinity of the wheels, or inside the wheels on the transmission side. Use pen and paper to record any unusual noises. Make note of any vibration or shudder you feel while engaging the transmission, or during acceleration or slowing down.

  3. 3

    Feel for excessive vibration. Vibration will point to play in the inner or outer bearings of the CV joint. A bent transaxle driveshaft will also cause a constant vibration, requiring a replacement of the shaft.

  4. 4

    Listen for a clunking noise when shifting the transmission into the drive position. This will be a problem with excessive slack in the CV joint or the transaxle inner gears. Clunking during acceleration will point to the inner gears of the transaxle itself. Inner gears that show excessive play in the transaxle will have to be replaced.

  5. 5

    Listen for a howling or "growling" noise at all times while driving. This will point to worn wheel bearings in the CV joint, which includes the drive wheel section near the axle hub. This requires replacement of the inner and outer wheel bearings.

  6. 6

    Feel for a shimmy or shudder at low speeds. This can point to an improperly tightened (torqued) axle wheel nut, which allows excessive play in the bearings and lets the wheel wobble. Loosen the axle nut and re-torque it to specifications.

  7. 7

    Locate the problem wheel once you have finished the test drive. Place the vehicle in park or neutral with the emergency brake set. Lift the front end of the vehicle and place a jack stand under the frame near the wheel. Inspect the CV joint lubrication boot (the large rubber bell-shaped object) and make sure it has no cracks in the rubber, that the large hose clamp remains tight and intact and that the boot has not deflated. Improper lubrication at the boot will cause excessive wear on the CV joint, and requires replacement of the CV joint.

  8. 8

    Remove the wheel from the suspect (noisy) side of the front end with the tire iron. Look carefully at the axle nut. Make sure it sits flush (tight) against the axle hub. Pull the wheel back and forth (toward you) and note any excess play in the wheel. Excess play will point to an improperly torqued wheel bearing nut or a lack of grease lubrication. The wheel bearing should be lubricated and re-torqued, or replaced if worn.

Tips and warnings

  • Do not attempt to drive a vehicle that has a frozen transmission. The stress can cause other drive line components to break. Have the vehicle towed.

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