: Transmission flush?

01-13-04, 11:35 PM
When should this be done? I do not have any service records on my recent purchase of my 97 deville. So should this be done to be safe? If so how much is it? and what is done? what will it help?

Big Jim
01-14-04, 04:54 AM
In '94, the recommended interval is 100,000 miles. I've seen several different cars that recommend the same. In my opinion, that is way too long. A rebuild can run close to $4000. If a $100 flush a couple of times extends the life of the tranny, it is a good investment. I've gotten in the habit of doing any used car I buy shortly after I get it. You really have no clue what the transmission has been through so don't take chances. I'm leaning toward 50,000 mile intervals on most cars and about 30,000 on the wife's PT because Chrysler has become notorious for early transmission failure.

01-14-04, 09:26 AM
Definitely extends trans life. I'm amazed that the suggested intervals are so long.

01-15-04, 11:15 AM
Under normal operation the trans fluid can easily go 100K.

Remember that the trans fluid is not exposed to gas, water and combustion byproducts like the engine oil is and the trans oil is kept cooler than engine oil so it does not degrade thermally nearly as fast.

If you want to service the trans , then by all means drain the pan, change the filter/clean the screen and refill with fresh fluid. DO NOT, however, be tempted to have the trans "flushed". There have been many documented cases where transmissions that are operating fine suddenly die soon after a flush. Whether it is from debris stirred up by the flush, debris introduced during the flush from the flushing equipment, poor quality "bulk" oil or whatever it happens.

Transmission flushes are a "feel good" item that are being heavily marketed by trans shops and some dealers as they are a big money maker. Forget about them. They can do far more harm than good. Consider the fact that most people never do anything to service their trans. Then, one day it starts to fail. Usually, when an automatic trans starts to fail it starts generating copious amounts of debris internally. So, the first thing the drive does is to go to the trans shop for a trans "flush" in the fervent hope that the flush ("best thing going...pamper your trans") will somehow magically heal it. In the process the flushing equipment is heavily contaminated with the debris from the trans. Now, you come along for a "flush" to feel like you are pampering your trans. The shop or tech hooks up the lines wrong, uses the same old fluid over (recycles it to save money), forgets to clean the lines, etc....and, YOUR trans gets the debris in it. Forget about exposing yourself to the risk...or exposing your trans to the risk.

I realize that there is some fluid trapped in the torque converter and trans. If you really really want to fell like you changed all the fluid (it really isn't necessary for a regular maintenance) take a cooler line loose at the radiator, route it to a bucket, start the engine and let the trans pump move all the oil from the trans into the bucket while you pour fresh fluid into the pan. Do this after the pan has been removed/replaced and the filter/screens replaced/cleaned and you will effect a complete oil change without subjecting yourself to the risk of a flush.

Face it...would you get a blood transfusion from an unknown source?? Why do this to your trans no matter how great it seems.

On the 4T60/65E trans change the fluid cold so that almost all of it will be in the lower pan. The side cover has a thermostatic valve that traps oil in the side cover when hot, so, if yuo change it when hot, there will be oil in the side cover that is not accessible.

On the 4T80E trans (Northstars) there is no filter to change in the lower pan. Just the two pickup screens that should be cleaned. The filter itself is in the side cover and is sized so that it never needs to be replaced for normal service as it is inaccessible unless the trans is removed from the car. There is also a drain plug hidden under the bottom pan, that drains the side cover. The 4T80E is a dry sumped unit that scavenges the oil from the bottompan and stores it in the side cover. Hot or cold, there will be very little oil in the bottom pan. Most of it is in the side cover. After the bottom pan is removed the drain plug for the side cover storage area is visible. Be sure to do the side cover drain also.

Once again, avoid the trans flush. It is simply not required nor a good idea.