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How to Find out if a Transmission Has Gone out

from wikiHow - The How to Manual That You Can Edit
The main parts of a car transmission are (starting from the engine) the clutch, gearbox, dispatch box (for 4x4 vehicles), the drive-shaft, the differential and the tires. This article will help you diagnose a failing transmission. In the tips section is an overview of symptoms that indicate a problem in these parts.

Steps

Manual Transmission
  1. Park your car with its front tyres touching the curb. Engage 1st and start slowly releasing the clutch pedal without applying any throttle. The engine should gradually fade out and bog down when the pedal is completely released. If the engine just bogs down at some point, or the fading is not gradual, the clutch is damaged. If the gearbox grinds when you try to shift in first from a standstill, there's a damage in the clutch too.
  2. Try to pull off in 3rd gear with the front wheels at the curb, and without applying throttle. If the engine doesn't die, it shows a complete clutch failure. In that case, do not drive this vehicle.
  3. Find a smooth, straight road to test the vehicle. Start from first, and slowly accelerate from second. As you do this use late-shifting, i.e. slightly over-rev the engine (approx. 500-1000 RPM faster than the revs you'd normally shift at). Up-shift to second without using double-clutching. Repeat the same procedure when shifting into 3rd. Now, with your car running at approximately 50 km/h (25 mph) try down-shifting to second without double-clutching. Both the up-shifting and the down-shifting must be done without grinding. Grinding of the gears indicates a gearbox malfunction, most likely in the sync gears ("synchronizers"). To make sure it's the synchronizers, try up-shifting and down-shifting with double-clutching. If the grinding stops, then it's the synchronization.
Automatic Transmission
  1. Park your car with the front tyres touching the curb with the gearbox in Drive. Start applying throttle smoothly. The car must slowly climb over the curb without the engine fading.
  2. Shift into drive and hold the break pedal after making sure your brakes work. Press the gas pedal all the way down. The engine should not fade. If it does, it means the transmission (particularly the clutch) does not disengage completely.
  3. Check for smooth shifting. On an even and relatively horizontal road you should be able to accelerate without any tangible jolts. If there are such, the gearbox has malfunctioned.
  4. Check for vibrations. Driving at about 70 km/h (35 mph) switch to Neutral (both auto and manual). There shouldn't be any lateral vibrations. If there are, this is either due to a warping of the drive-shaft, or a suspension damage. Basically, drive-shaft warping is perceived as a vibration in both vertical and horizontal direction, whereas a suspension damage is felt as a vibration in only one direction (i.e. either horizontally or vertically).
  5. Test steering. When trying to enter a corner with approximately 30 km/h (15 mph) there shouldn't be any tangible under-steer. The presence of such may be due to a differential failure, especially in FWD cars. Novice drivers must never try and test their differentials by trying to induce under/over-steer!

Tips for preventing transmission damages

Tips

Warnings

Article provided by wikiHow, a wiki how-to manual. Please edit this article and find author credits at the original wikiHow article on How to Find out if a Transmission Has Gone out. All content on wikiHow can be shared under a Creative Commons license.