Transmission PerformanceFresh transmission fluid with the proper levels of additives replaces old fluid with depleted additives. The old argument is that oil never wears out; however, the additives that oil manufacturers add to the oil, to give it certain properties and qualities do.
InspectionRemoving the pan allows the technician to inspect the contents of the pan fully for telltale signs of potential trouble. All contaminants do not get trapped by the filter. Contaminants may also settle in the pan and this contaminant can be “read” by a competent technician.
The condition of the fluid can also indicate potential failure. Having the car on the hoist, allows the technician to inspect the entire transmission for other problems(including leaks at points other than the pan gasket). It is also a good time to check connector and wiring problems and any road damage.
Contamination RemovalTransmissions generate contamination as they wear. These contaminants interfere with the operation of valve bodies and solenoids and accelerate the wear of hard parts. Replacing the filter and cleaning the sump pan removes contaminants from the system, reducing the possibility of component failure.
Most owner’s car manuals say it isn’t necessary. Yeah, right. That’s why transmission shops are kept busy replacing burnt out automatic transmissions.
For optimum protection, change the fluid and filter every 50 000kms /24mths on standard vehicles or 25 000kms/ 12mths on commercial / severe usage( i.e. towing) vehicles.
Why ATF (automatic transmission fluid) Wears Out
An automatic transmission creates a lot of internal heat through friction. The friction of the fluid churning inside the torque converter, the friction created when the clutch plates engage, and the normal friction created by gears and bearings carrying their loads.
It doesn’t take long for the automatic transmission fluid (ATF) to heat up once the vehicle is in motion. Normal driving will raise fluid temperatures to 80 degrees C., which is the usual temperature range at which most fluids are designed to operate. If fluid temperatures can be held to 80 degrees C., ATF will last almost indefinitely — say up to 160,000 km. But if the fluid temperature goes much higher, the life of the fluid begins to plummet. The problem is, even normal driving can push fluid temperatures well beyond safe limits, and once that happens, the trouble begins.
At elevated operating temperatures, ATF oxidizes, turns brown and takes on a smell like burnt toast. As heat destroys the fluid’s lubricating qualities and friction characteristics, varnish begins to form on internal parts (such as the valve body), which interferes with the operation of the transmission. If the temperature gets above 125 degrees C., rubber seals begin to harden, which leads to leaks and pressure losses. At higher temperatures the transmission begins to slip, which only aggravates overheating even more. Eventually the clutches burn out and the transmission calls it quits. The only way to repair the damage now is with an overhaul — a job which can easily run upwards of $1500 on a late model front-wheel drive car or minivan.
As a rule of thumb, every 15 degree increase in operating temperature above 80 degrees C. cuts the life of the fluid in half!
At 90 degrees C., for instance, fluid life is reduced to 80,000 km. At 110 degrees, which is commonly encountered in many transmissions, the fluid is only good for about 60 000km. At 120 degrees C., the fluid won’t go much over 15,000 km. Add another 20 degrees, and life expectancy drops to 8000kms. Go to 150 degrees C., and 1,000 to 1,500 klm is about all you’ll get before the transmission burns up.
If you think this is propaganda put forth by the suppliers of ATF to sell more fluid, think again. According to the Automatic Transmission Rebuilders Association, 90% of ALL transmission failures are caused by overheating. And most of these can be blamed on worn out fluid that should have been replaced.
On most vehicles, the automatic transmission fluid is cooled by a small heat exchanger inside the bottom or end tank of the radiator. Hot ATF from the transmission circulates through a short loop of pipe and is thus “cooled.” Cooling is a relative term here, however, because the radiator itself may be running at anywhere from 85 to 105 degrees C.!
Tests have shown that the typical original equipment oil cooler is marginal at best. ATF that enters the radiator cooler at 150 degrees C. leaves at 115 to 135 degrees C., which is only a 10 to 20% drop in temperature, and is nowhere near good enough for extended fluid life.
Any number of things can push ATF temperatures beyond the system’s ability to maintain safe limits: towing a trailer, mountain driving, driving at sustained high speeds during hot weather, stop-and-go driving in city traffic. Problems in the cooling system itself e.g.a low coolant level, a defective cooling fan, fan clutch, thermostat or water pump, an obstructed radiator, etc., will also diminish ATF cooling efficiency. In some cases, transmission overheating can even lead to engine coolant overheating! That’s why there’s a good demand for auxiliary add-on transmission coolers.
ATF Fluid Types
What kind of automatic transmission fluid should you use in your transmission? The type specified in your owner’s manual or printed on the transmission dipstick.
CAUTION: Using the wrong type of fluid can affect the way the transmission shifts and feels. Using Type F fluid in an application that calls for Dexron II may make the transmission shift too harshly. Using Dexron II in a transmission that requires Type F may allow the transmission to slip under heavy load, which can accelerate clutch wear.
Changing the Fluid
It’s a messy job because there’s no drain plug to change the fluid, but you can do it yourself if you’re so inclined. To change the fluid, you have to get under your vehicle and remove the pan from the bottom of the transmission.
When you loosen the pan, fluid will start to dribble out in all directions so you need a fairly large drain pan. You should also know that removing the pan doesn’t drain all of the old fluid out of the transmission. Approximately a third of the old fluid will still be in the torque converter. There’s no drain plug on the converter so you’re really only doing a partial fluid change. Even so, a partial fluid change is better than no fluid change at all.
A typical fluid change will require anywhere from 3 to 6 litres of ATF depending on the application, a new filter and a pan gasket (or RTV sealer) for the transmission pan. The pan must be thoroughly cleaned prior to reinstallation. This includes wiping all fluid residue from the inside of the pan and scraping all traces of the old gasket from the pan’s sealing surface. Don’t forget to clean the mounting flange on the transmission too.
When the new filter is installed, be sure it is mounted in the exact same position as the original and that any O-rings or other gaskets have been properly positioned prior to tightening the bolts. Then tighten the bolts to the manufacturer’s recommended specs.
When refilling the transmission with fresh fluid, be careful not to allow any dirt or debris to enter the dipstick tube. Using a long-neck funnel with a built-in screen is recommended.
CAUTION: Do not overfill the transmission. Too much fluid can cause the fluid to foam, which in turn can lead to erratic shifting, oil starvation and transmission damage. Too much fluid may also force ATF to leak past the transmission seals.
Add 500mls at a time until the dipstick shows full. The transmission really isn’t full yet because the dipstick should be checked when the fluid is hot, and the engine is idling with the gear selector in Park/Neutral. So start the engine, drive the vehicle around the block, then recheck the fluid level while the engine is idling and add fluid as needed until the dipstick reads full.
Over the past 15 years there has been a technological explosion in the automotive industry. Advancements in miniaturization, computers, hydraulics and material technology have all combined to make your vehicle safer, more efficient and more complex than ever before.
Why is servicing your transmission important?
It is very important for a transmission to be serviced on a regular basis. We recommend you get your transmission serviced every 50 000kms /24mths on standard vehicles or 25 000kms/ 12mths on commercial / severe usage( i.e. towing) vehicles. This will ensure that the transmission is thoroughly checked and minor repairs fixed before they cause major breakdowns. Most car owners do not know that a transmission exists in their car until a problem occurs. Transmissions need to be serviced before a problem occurs – never wait for a problem to occur.
An auxiliary transmission fluid cooler is easy to install and can substantially lower fluid operating temperatures. The plate/fin type cooler is somewhat more efficient than the tube and fin design, but either can lower fluid temperatures anywhere from 25 to 160 degrees when installed in series with the stock unit. Typical cooling efficiencies run in the 35 to 50% range.