Transmission trouble: What every car owner must know

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An internal view of an eight-speed automatic transmission from a 2009 BMW.

A BMW 2009 eight-speed automatic transmission. (Photo: Flickr; Archivio Perini)

Few things cause the average auto owner to cringe like the mention of transmission trouble. All most people know is that it sounds expensive. However, with some basic transmission knowledge and proper transmission maintenance, replacing a transmission can be avoided until absolutely necessary. For some cars, that time may come around 200,000 miles, although as you’ll see, there are many variables involved that can lessen that figure. Some last 80,000 miles or fewer.

A transmission is no trouble if you understand it

Part of avoiding transmission trouble involves understanding what a transmission does for your car. It is a key component in the drivetrain of your vehicle; the drivetrain consists of those components that generate power and transfer it to the road surface so that the vehicle moves forward. Automobile transmissions come in automatic and manual varieties, and in both cases, gears shift in order to maintain the car’s momentum.

While all of the internal workings of a transmission are somewhat complex, here are the four basic systems, as outlined by

  1. Bell housing: The cone-shaped metal casing. If your car is front-wheel drive, it will be visible under the hood and off to the side of the engine. Rear-wheel drive cars house the transmission under the car and behind the engine.
  2. Gears: These are broken down into main and planetary segments. These are essential to an engine’s function.
  3. Fluid: The red fluid in an automatic transmission. It lubricates the gears of an automatic transmission so that excessive heat build-up doesn’t cause the parts to break down and cause real transmission trouble.
  4. Filter: Eventually, transmission fluid becomes dirty and needs to be changed. The transmission filter catches particles and build-up. Many early transmission trouble issues can be helped by changing the filter.

How long does a transmission last?

If you practice proper transmission maintenance, “as long as possible” is the general answer. More specifically, however, the answer depends upon how you drive, the environment in which you’re driving, the type of transmission fluid you use and the construction of your transmission (as a mass-produced part, it will vary greatly by manufacturer). Unfortunately, much of the data on that final point is anecdotal. Thus, it’s best to focus on the other aspects.

According to How Stuff Works, transmission fluid should be checked and changed regularly, at least twice per year if not more often. Severe use of your car (more than 50 percent of driving time spent in heavy city traffic in temperatures above 90 degrees Fahrenheit) generally warrants the use of a 15,000-mile transmission fluid and filter change interval. Various grades of transmission fluid exist (more than 50 types), and each is rated at a different level of slipperiness for your car’s specific gear ratio. Check your owner’s manual for more information on what is appropriate for your transmission, usage and driving conditions.

Is there a transmission fluid leak?

If your transmission doesn’t seem to shift clearly, transmission trouble could be on the horizon. According to How Stuff Works, some places to check for red fluid leaks include:

  • Base of the filler tube
  • Drain hole underneath the transmission
  • Between transmission and engine
  • Selector shaft – The rod connecting gear shift to transmission
  • Speed sensor mounting point – Either a cable running into the transmission housing or a sensor that’s bolted directly to the transmission housing
  • Radiator – Red transmission fluid doesn’t mix with radiator fluid, so it should be easy to spot it floating around in there

Serious transmission trouble is not a task for the average DIYer

If maintaining the proper fluid levels and replacing the filter don’t save you from transmission trouble, consult an ASE-certified mechanic with Blue Seal repair facilities. According to Cost Helper, replacing a transmission can cost anywhere from $1,800 to $3,500. The figure will vary depending upon labor costs and your make of vehicle. Try to find a mechanic who will offer at least a limited warranty on the replaced transmission. Rule of thumb is the more your car costs, the more it will cost to replace the transmission.

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How Stuff Works

How to change transmission fluid:

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