Tranny 'flush' or Filter change

[Silvertwinkie]

[i]Originally posted by trumpwer

But some trans fluid is not pink to start with?
We were discussing this this weekend. Heat kills transmissions, I wondered about putting a temp gauge on the transmission, someone said the fluid in the cooler runs along side the radiator coolant, so if your engine temp gauge is OK, your trans is OK. Makes sence, but I am not sure it's accurate. Anyone know for sure? [/b]

Not even accurate by a longshot. The trans although most do have an oil to water cooler in the radiator, it does NOT mean at all that the trans will remain at or below the engine coolant temp at all! I can prove this by my trans gauge I have installed on my car. The engine temp is about 175 degrees when towing in 90 degree outdoor temps and the trans is at about 195 degrees. Using the logic above, the trans should be at 175 degrees as well. It won't for two reasons. First, oil and water heat and cool at different rates. Although the oil to water cooler in the radiator helps, it by no means suggests that if the engine temp is ok, your trans is too. Second, the trans is the hardest working part on a car. It can flash heat far quicker than an engine due to the massive stresses placed on the torque converter and the internals.

You need to have a trans gauge to know for sure how much different the temps are. If you start towing up a hill, I 110% promise you that your trans temp gauge will show an fast increase in temp faster than the engine will.

Here is what I have done to keep the trans cooler besides the typical oil to water cooler that is inside the radiator:

Installed an air scoop torque converter cover. It can be found at this site: http://www.clearimageautomotive.com/...Drivetrain.htm

Second, I have installed the deep pan Chevy truck trans pan to my 4l60e transmission. It adds 2 extra quarts to the overall oil in the trans. The thought to this is simply that more oil take a bit longer to heat than less. For example, if you place a pot of cooking oil on the stove a high heat and a pot that is 1/4 less, the one with less volume will heat faster. Same holds true with your trans. Towing I consider a very high heat generator, especially when the torque converter is not locked.

Third, on my car, GM installed a oil to air cooler for the trans, so after it initially gets cooled by the unit in the radiator, it then is piped to a mini seperate radiator as well. The problem I saw was that GM placed it on the Impala directly behind the bumper so that it got minimal airflow. What I did was cut a rectangle hole in the bumper cover that allows air to directly hit this oil cooler thereby lowering the trans temps. If I am going 55mph, I have 55mph air blowing through my trans oil cooler just like the regular radiator gets. Also works like a charm.

Fourth, I converted the trans oil to Mobil 1 fully synthetic. It's thermal tolerances are 200% superior to standard conventional oils.

Fifth, I have changed my thermostat from the standard 185* unit to a 160* unit which does have an effect on overall cooling of the engine and trans compnents. I can do this with my reverse flow LT1 engine without any adverse effects. However, some conventionally cooled engine may develop issues with thermostats that are lower. This is not an issue with an LT1 (Corvette) engine since the PCM goes into closed loop at 147 degrees.

Sixth, I have had my PCM (main computer) reprogrammed to have the secondary cooling fan turned on at a lower temp if the car is under a certain MPH or the A/C is on.

Last to monitor the temps, I installed a trans temp gauge in the car. Works fantastic. I took the car and a fully loaded Bambi with the fresh water full up a steep grade hill that was about 3/4 long. The trans barely exceeded 200 degrees, while the engine was at 187 degrees.

One last comment on the transmission is simply that it should be changed more frequently if towing. If the service book says 50k, I do it at 25k or even earlier. Some say it's a waste, but I regularly get 150k+ out of my transmissions that are used for towing. It is 110% accurate that a flush that evacuates all the oil will require significantly more oil to replace compared to a trans that just had the pan dropped and the filter changed. How much depends on the design of the trans--- they are as different as there are engines out there.

Hope this helped. I have spent almost a year researching the best towing tools to have for my particular car and spent a GREAT deal of time on the drivetrain part which includes the transmission and it's cooling needs for severe duty use.

BTW, I flush it out every 2nd or 3rd change. The rest of the time I just drop the pan, change the filter and refill. I also have dual magnets in the pan to collect as many metal particles as possible, not that the filter doesn't do a great job itself.

Also, do not forget to change your differential oil, power steering oil and brake fluids and coolant as well. Most folks worry only about the trans fluid, coolant and the engine oils. There are a few more systems than need to be flushed and refreshed to keep the components all happy.

Eric

[Raptorrider2001]

My Duramax manual says to change the fluid at 25k if you tow or do a lot of city driving. A complete change is around 19 qts. Just the pan and filter is almost 8. As to trans. breaking down after a fluid change, this often happens on a high mileage tranny that has not been maintained, according tto a tranny mechanic friend. The new fluid's additives break loose sludge and crud and this causes trouble in the valve body and leads to problems. It is a gamble changing the fluid on a high mileage tranny so you have to decide the risks. At 80k on my wife's mini van, I went ahead and changed it with no problems. Just lucky I guess.

[59toaster]

Originally posted by jcanavera


Interesting. That's interesting Jeff. I thought I remembered that the torque converter held 4 to 5 quarts. I'm curious about this. I'm going to see Patty's cousin's husband this weekend. He owns a auto repair business and he used to do my transmission oil changes on my previous vans. Something rings bells that the quantity of fluid used when I did a filter change was much more than 5 quarts.

BTW, if you have a second call me at work tomorrow I have a request for you.

Regards,

Jack

I think the confusion is between quarts and pints. Trannys are rated in pints no quarts. 12 pints in the converters sounds about right for a transmission like a 4l60 or 4l80. My TH400 is rated at 22pints total capacity. I just serviced it this weekend. Owners manual said 9.5 pints on a service including dropping pan and changing filter.

I have put in 5 quarts (10 pints) and still reading a pint low. The distance from add to full on a Auto dip stick is 1 pint for most manufactures, not one quart like an engine.

[overlander63]

Thanks for your quick reply Kevin!

That's kind of what I thought was best.

You have the setup that I need to buy; the 7.4L - 2500 Burb!

Did you give much thought to the synthetics for trans or rear end? Since it is already heavy duty, perhaps it is less important than with mine which is undersized (Expedition).

Steve

Steve, most Expeditions have a drain plug on the torque converter to drain that as well as the transmission when servicing. Look for a rubber plug on the bottom of the bell housing.
If it has one, rotate the engine until you find the drain plug, and remove it to drain it.
Remove the transmission pan and filter, replace the filter and gasket, replace the drain plug, and fill it up. It should take 8-10 quarts. Make sure you specify if it is two or four wheel drive when getting your filter, as some 2wd E4OD's take different ones.
Happy Tranny-ing.
Terry
(in Florida)

[RichardT]

I will never have a tranny flushed again, I have a T400 that was totally rebuilt with 14000 mi on it, I deciede to have it flushed on a trip during an oil change pit stop and I had troubles with it on way home and now it is sticking so bad and wont shift correctly, BTW, no problems at all before fluid flush.