The phrase “if it ain’t broke, don’t fix it” doesn’t apply to vehicle maintenance. If trouble’s brewing beneath the bonnet, it’s cheaper and easier to get it fixed while the problem is still small and manageable.

You should periodically pay attention to different parts of the car, starting with the automatic transmission, if you drive this type of vehicle. The automatic transmission system is perhaps the most complicated component of the car with mechanical, hydraulic and electrical systems as well as computer controls. It is one of the most expensive parts to repair, so it’s good to know how to maintain the transmission to avoid costly repairs.

The automatic transmission fluid should be checked while the engine is running. The car should be on a level surface and the parking brake engaged. The gear should be in “P” or park position. Locate the transmission dipstick, which is usually behind the oil dipstick.

With the engine running, extract the dipstick, wipe it clean with a clean cloth and reinsert it. Pull it out again to obtain the correct reading.

• Change in fluid colour, odour and level
  

  Transmission fluid is a red transparent oil that turns brown over time. If it is very dark in colour, a change of transmission fluid is probably overdue. The fluid shouldn’t have a burnt smell either.

  Drop a small amount of fluid on a white piece of paper. The fluid should appear clean and transparent, without any metal filings or black flakes.

  The level of the fluid should be between the maximum and minimum markings. The automatic transmission is a sealed system, so the fluid level shouldn’t be excessively low. A low level could mean a leak in the system, such as a worn seal or a crack somewhere.

  Even if the fluid looks fine, it’s a good idea to follow the car manufacturer’s recommendation to change the fluid after clocking a certain mileage.

• Leaks under the car
  

  If there is a persistent red oily leak coming from under your car, check to see if it is coming from your transmission or the power steering system. Leaks from the power steering system can appear on the ground in roughly the same areas as transmission leaks. You will need to a mechanic to fix the problem.

• New noises, vibrations and shift behaviour
  

  The transmission should shift smoothly and quietly under light acceleration; the shifts may be slightly more pronounced under heavier acceleration at higher speeds. You have cause for concern if shift points are erratic, or you hear noise or feel a strong jerk during shifting or detect whining noises coming from the floorboard.

  Another indication of a transmission problem is delayed engagement between gear shifts. Transmission should occur very smoothly, without strong jerks. The gears may slip if the transmission is excessively worn out. When that happens, the engine makes more revolutions per minute but the speed remains the same when you step on the accelerator.