Tranny 'flush' or Filter change

[Sav'h Steve]

Tranny 'flush' or Filter change

I just took in my LeSabre for transmission filter change and the reputable shop recommended a tranny flush vs the filter change.

He said that the flush changes ALL the fluid (he used and charged for 17 quarts of ATF on a V-6) and "is better than just the filter and add fluid method" which is what I grew up with.

I went ahead with the flush. But for my towing vehicle I was wondering what the current BEST method is to do. Maybe doing both? Also thinking that I may want to do both on the first service at about 30,000 and go with a synthetic and douse the dino!

Since the tranny gets the most abuse, I think it needs the most attention. Current vehicle is a 1/2 ton with an 'underweight' transmission.

This was posted in Motorhome section and fangthorpe replied:

"Full change is not that big a deal. Drop pan, change filter, fill pan-maybe 30-40 minutes. Pull IN hose - usually the bottom one - off the radiator, run the motor a little, pump old fluid into a bucket, replace hose, refill trans, clean up driveway - maybe 30 mins. Cost $35 for filter and fluid. Look for fine junk in the pan."

His reply doesn't sound that hard! Run engine till fluid slows?

I do anything on the trailors but shy from motors and transmissions (but may start some if routine and expensive.) From some of the other experts or those who have consulted from the specialists, what is the best route?

Steve in Savannah

[overlander64]

Greetings Steve!

I have had my GM dealer service my Suburban since it was new. He suggested the total flush approach along with draining and a new filter at my first service interval (30,000 miles). I have now had this process repeated three times (truck now has 108,000 miles) and the truck still performs as if it were new. It is a K2500 with 7400 VORTEC and a special order heavy duty transmission package - - over 80% of my towing is in overdrive (at least 42,000 miles of overdrive towing at this point) and no problems of any kind with the transmission.

Good luck with your decision!

Kevin

[Sav'h Steve]

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

[jcanavera]

Originally posted by overlander64
Greetings Steve!

I have had my GM dealer service my Suburban since it was new. He suggested the total flush approach along with draining and a new filter at my first service interval (30,000 miles).
Kevin

Kevin,

Let me understand what you just said. The dealer said do a total flush (which means replacing all the fluid). Then drain what he just put in and change the filter? If so you have just thrown out the majority of your new fluid. I'm confused.

jack

[airstreamer01]

Flush & Filter. Because the torque converter holds approx 12 or 13 quarts, so by just doing the filter you end up mixing your clean 4 or 5 quarts with 12 or 13 quarts of dirty fluid. If you go to the synthetic fluid runs cooler and will not breakdown like regular tranny fluid. Heat kills transmissions so cool is good. Years back they did not have the equipment to flush, so you really should have done it more frequently, but will total flush you can spread out the intervals alittle.

[53flyingcloud]

Kevin

I'm curious about the requirements for your interval. Under normal driving conditions, I can see you going 30k but, when you're towing your unit does your owners manual say anything about changing it, say..closer to 6k miles interval?

Maybe the requirements for my diesel setup is different..
I do the same thing here flush/change the oil/filter at the begining/after each towing season or 6k miles whichever comes first while towing. Rear end gets done as well with the tranny.
BTW, I use Amsoil products all the way around.

ciao

[Gene Wissink]

I got a 96 dodge 1500, 104k and I have seen various posts about what type of fluid to use in them, some say to go to atf4 even if dextron is on the dipstick. I got no owners manual with the truck so I am in the dark on this, even what weight oil to use, it sure likes to use 10-30, I think I will go heavier.

[jcanavera]

Originally posted by airstreamer01
Flush & Filter. Because the torque converter holds approx 12 or 13 quarts, so by just doing the filter you end up mixing your clean 4 or 5 quarts with 12 or 13 quarts of dirty fluid.

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

[overlander64]

RE: Exact Procedures in Transmission Service

I honestly don't ask that many questions of my servicing dealer. My family has done business with the same dealership since 1961, and we have ALWAYS patronized their service department following the service managers suggestions for regular service. Over the years, we have had a number of cars exceed 200,000 miles with virtually no difficulties - - most recently our 1984 Oldsmobile Toronado with 215,000 miles - - our 1975 Pontiac Grandville Brougham Convertible 236,000 miles; and currently four of our cars have more than 100,000 miles with virtually no difficulties - - 1975 Cadillac Eldorado Convertible 110,000 miles, 1985 Oldsmobile Delta 88 Royale Brougham Luxury Sedan 100,000 miles, 1994 Chevrolet S-10 Blazer 117,000 miles, and 1999 GMC K2500 Suburban 108,000 miles. In all of the above instances, we have utilized the GM recommended fluids sold by our dealer, and followed the "severe service" guidelines as suggested by our dealership's service manager.

For at least the last decade, our dealer has maintained a service file for each vehicle owned by regular customers, and the service manager advises what services are due when you drop the vehicle off for its 3,000 mile interval service. Since I take a number of extended trips where some service may be performed by other dealers, my local dealer also notes the service performed by othes while I am on the road so that we are able to keep the vehcile on its scheduled maintenance path. In addition, we maintain a 3-ring binder in each vehcile that contains all of the receipts conerning that vehcile from the original sales invoice and order form through the most recent repair invoices.

I haven't had the time to look back in my records regarding the amount of fluid utilized in flush and fill operations. I do know that the cost of the flush/fill operation is approximately $75.00 higher than the usual fluid/filter change. Given the improved shifting response and smoothness of shifts with my '75 Eldorado, I can't complain about the cost of the service - - and historically, this dealer has never given us any bad advice regarding servicing our automobiles and light trucks.

Kevin

[Dbraw]

My 1990 half ton Chevy with a 350 has 165,000 miles on it. I don't think the transmission fluid has ever been changed or flushed. Should I flush it or leave it alone? No problems with shifting or pulling our 3,500 pound AS.
Dan

[Pick]

Dan, a mechanic once told me, "Change it often, or don't change it at all." I have heard a lot of horror stories of folks having the FLUSH done with high mileage trannys, then having them go bad within a week or so. It might be safer to just drop the pan, clean it, replace filter and refill. That way you will have at least infused the tranny with some depleted additives.

[Sav'h Steve]

I had a '90 Park Avenue that I bought with 100,000 on it. Never had the trans work done.

I went to about 7 dealerships in the Atlanta, Savannah, Jax areas and looked for the best info on doing tranny service work. Most said that as long as it is running fine, DON'T change the fluid.

The reason given was that it would likely dislodge some sludge and THAT would cause problems. So I just kept it full - adding any if needed. It went fine till 190,000 when I sold it. It was starting to have problems.

The tendency is to DO SOMETHING about it "to make it better", but I had to bite my tongue and just keep driving it.

STeve

[jcanavera]

Transmissions that are used for towing need maintenance. Be it either flush or dropping the pan and filter change method. Check the owners manual and most have a recommended interval. My new GMC manual I think recommends 50,000 miles when the vehicle is used for towing.

Another way to check is to look at the color of the oil. If its not pink it means that it has gotten hot and that means the fluid components are breaking down. Transmission fluid has no contaminents like engine oil so the change of color means its time to change oil. Even if you haven't reached the mileage as shown in your manual.

Some folks get away with out ever changing the transmission fluid, and some folks smoke and live to 100. I think the odds are with me if I change the fluid and don't smoke.

Jack

[trumpwer]

If its not pink it means that it has gotten hot and that means the fluid components are breaking down. Jack [/B][/QUOTE]

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?

[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.