I'm helping a buyer in California get her first car with an automatic transmission for under $4k. Not surprisingly, all these cars have issues. Despite their great reputation, Honda Accords and Civics model years 2002+ have greater than usual complaints about bad automatic transmissions.

What Toyota models, say from 1993-2004 Corollas or Camrys, are most reliable? Most troublesome with transmissions or other issues? As a parallel, Honda fans claim the 2000s era Accord V-6s have excessive torque that ruins automatic transmissions faster. Is this true for Toyotas?

Is there an upper mileage limit, eg 250k, that we should avoid in Toyotas, or is it mostly dependent on the car and maintenance history?

Are there any do-it-yourself automatic transmission tests that I can do during test drive that predict at least 20k more life in a transmission?

Mechanics and Google seem to believe that one should NEVER change automatic transmission fluid. Something about a benefit of old transmission fluid keeping sludge from jamming passageways. They add that soon after changing automatic transmission fluid, transmissions start to slip, quickly leading to death. It doesn't make sense to me, because old transmission fluid won't protect well or at all against the heat generated or keep the transmission clean. I wanted to see what those of you experienced with Toyotas believe.

Thank you!

 

As to determining when a trans might fail.

An auto trans can work just fine. Then one day fail to shift into forward or reverse. The
result being a stranded driver needing a tow and expensive repairs. Obviously the trans had some deterioration or wear but it didn't have any indications the driver noticed.

A trans can also give indications such as hard shifting, engine over revving between gears, slipping, delayed gear engagement, etc.

The trans pan can be dropped and inspected for excess metal and non-metallic clutch plate debris. A sign the trans is failing. The trans operates via hydraulic pressure to operate various valves, clutches, brakes, etc. Monitored hydraulic pressure during trans operation can provide an indication of its operational condition.

The internet has host of hits providing symptoms of a problem trans. Suggest reviewing these symptoms.

Unless a design problem (not common) or the trans is abused or pulling more trailer weight then designed for. Most trans fail because the trans fluid is overheated/wears out before it is changed. Trans fluid life is directly related to its operating temperature. The higher the temp, the shorter the life.

Transmission temperature/failure chart.

One can inspect the fluid for color and get an idea of its condition. On newer model cars, the manufacturers have color charts to compare the fluid color with. Then based on this make a determination of condition and when to change.

Ideally if a trans designed for conventional trans fluid has all it fluid changed say every 25-30K miles and is not abused, it should last the life of the car. Most owners never change the fluid.

Newer trans use synthetic fluid which is sometimes pitched as life time. These can last in theory 100K miles but it still needs to be changed from time to time. The synthetic fluid can withstand higher operating temps.

Issues of excess torque, etc should have been considered in the trans design for the engine power.

The problem with a used trans is one rarely knows what the trans maintenance was or if it was abused. Some one owner cars come with service records. One can check the fluid color via the dipstick. This assumes the trans fluid had not been changed prior to selling the car. The car can be driven and trans operation observed.

There is a theory that if a trans fluid was never changed. The clutch plates are now worn and the debris in the fluid is what is doing the gripping. The theory is changing the fluid cleans out the debris and thus there is nothing to grip.

The trans has about 1/3 of its fluid in the pan with the rest in the torque converter. The fluid can NOT be drained from the converter change via the drain plug on the pan. Just draining and refilling the pan will not change all the fluid.

To replace all the fluid requires a complete fluid change, sometimes referred to as a flush but they are not the same. There are machines which will force new fluid into the trans and the old out. Not all machines work the same way to do this. Chemicals can also be used to help clean the trans debris out.

During the flush process (more so when using cleaning chemicals), debris can break loose and get into the trans body which controls shifting. The clutch plates can become too clean and now start to slip.

It is the opinion of some, that ideally the transmissions own fluid pump be used to push out the old fluid will new fluid is available to replace it. No chemicals being used. This process gently removes the old fluid and replaces it with new. Trans debris is not dislodged, clutch plates are not cleaned or washed of debris.

Trans fluid wears out with heat and usage. Never changing the fluid means over time its condition will just get worse. As stated previously overheated and worn out fluid is the No 1 cause of failure. Never changing the fluid to keep from having trans issues although having some merit greatly increases the changes of trans failure over time.

As to what you can do. Pull the trans dipstick and put a few drops of fluid on a paper towel. Compare the color with those available on the internet if a search is conducted on trans fluid color and condition.

If the trans doesn't have a dipstick, one will need to go under the car to find the drain plug.

Drive the car trans fluid cold and hot on roads of all types. The trans should shift from Park to whatever gear without excess delay and harshness. The trans should up and downshift smoothly without slipping, delay or harshness. Sometimes a failing torque converter can cause a shake when accelerating. Be observant if any of the symptoms you noted in your internet search are present when driving.

Dropping the pan will show if there is excess debris.

 

Thanks!

Do properly cared for Toyota transmissions have an average lifespan rating, like computer hard drives have ratings for mean time before failure (MTBFs)?

Also, is one brand of synthetic ATF better than the others?

thanks

 

There is no MTBF stated for transmissions. The vehicle maker warrants the product for say a max of 100K miles. Many makers say little about trans maintenance beyond inspect fluid.

Obviously a hard drive (HD) may fail sooner if the computer is subject to hard impacts when used, the HD sees high operating temps, power problems (surges, brown outs), etc. A transmission would be no different.

An auto trans can last well over 300K miles. However recently someones failed at around 156K and can only speculate why. In my opinion the key to long trans life is regular fluid changes (all fluid) and not abusing the trans. Which includes coming to a complete stop before shifting trans gear directions and not shifting between F and R harshly if getting stuck.

As to synthetic ATF. A trans is basically a hydraulic controlled set of gears boxes. Differences in fluid viscosity, chemistry, etc (a different brand or type of fluid other then what the manufacturer recommends) can cause changes in its operation.

Stick to the type of fluid (or equivalent) the trans was designed to use. Such as Dexron II and III, Type I, II or IV and WS. Toyota changed the fluid type over the years in its vehicles eventually using synthetics. Toyota sells its own branded fluid thus at times one must find an equivalent in another brand if not wanting to buy from Toyota.

The issue is finding out what the equivalent fluid is an a synthetic or non-Toyota brand synthetic. Here you need to do an internet search of ATF fluid vendor sites to find the equivalent such as at the link below:

http://www.carquestprofessionals.com...%206.10.13.pdf

Plus suggest a search of user sites of owners who actually made the fluid change.

For trans designed for say Dexron II and III there as some synthetics that work just fine but have a slightly different shifting styles (for lack of a better word). This is OK but it is a slight difference in operation the driver may notice.

For you, determine what cars you are interested in. Once found determine what type of trans fluid it uses. This can be found on the internet and is stamped on the trans dipstick (if is still has one). You can extend this finding the trans model which can be found on the internet or on a sticker on the side of the drivers door.

Then do a search of fluid vendor sites and sites where users have actually used a different fluid in this case replacing mineral with synthetic. You will soon narrow down the choices.

All synthetics are very good. There differences are in chemistry, viscosity, etc. These difference can cause trans functional differences in a trans (unlike an engine). This is because a trans is designed for a narrower fluid parameter spec then an engine is.