ATF questions

[cerberusiam]

perhaps I'm using the term flush improperly, maybe the dealer shop is only doing an exchange?



I've read in a few different places that some guys unhook a line to the transmission cooler and pump all the fluid out by running the engine until ATF stops flowing, what do you guys think of that method?

Check and make sure thats what they are doing. Most of them have those machines now and a dealer should realize thats the only way to do it with any efficacy.



These machines do essentially the same thing as unhooking the return cooler line and routing it into a container. They tap into the line to route the old fluid into a container that has a bladder seperating the old fluid form the new. As the old fluid fills the container it forces the new fluid into the trans.



You can do the same thing by yourself in the drive way by just removing the rear cooler line and routing it into a bucket to catch the old fluid. It takes at least 3 times refilling and about 20 quarts to fully flush all the old fluid out that way but it works.

 

[rscurtis]

If you have the time, loosen the 10 valve body mounting bolts and let it sit overnight. You'll drain about 12 qts. of fluid. Retorque to 100 INCH pounds. While you're at it, install a drain plug in the stock pan. MH's idea of measuring the quantity of drained fluid is an excellent suggestion, I do it with coolant changes also, that way you know the system is full and not airbound.

 

[RChriste]

You can do the same thing by yourself in the drive way by just removing the rear cooler line and routing it into a bucket to catch the old fluid. It takes at least 3 times refilling and about 20 quarts to fully flush all the old fluid out that way but it works.

So are you saying that I should be adding fluid as I pump the old out?



My apologies to the OP for hijacking his thread.

 

[cerberusiam]

I add 6 quarts to start when changing the filter, start it in neutral and watch the fluid flow. When it slows to about half of what it started at I shut the engine off and refill with 4 quarts. I go thru 20-22 quarts to fully exchange the fluid to the point it starts looking good and bright again.



You cannot do a full exchange with only the fill of 16 quarts. When the transmission is in fluid coupling part of the fluid is dumped back to the sump and part is routed thru the cooler so you have to extend over that to flush as much of the old fluid out as possible. If you do the change when the fluid is relatively hot it flushes better.



Actually, the most effective way is put the truck on jack stands and use a lockup switch to pump more fluid thru the cooler when draining to a pan.

 

[DZink24]

last week i swapped out my transfer case ATF4, and i am currently reading into doing something with my 48RE. i am about to roll 60k and have never had anything done to the transmission. i am concerned about breaking something that works, so i was planning on just dropping the pan and however much fluid comes out, the filter and gasket. and replacing the equal amount of old ATF with new fluid. i figure at the least, it will get several qts. of fresh fluid in the transmission and a fresh filter.

 

[cerberusiam]

i was planning on just dropping the pan and however much fluid comes out, the filter and gasket. and replacing the equal amount of old ATF with new fluid.

You can and quite likely get away with that. A lot depends on how you use the truck.



At 60k your double the reccommended change mileage, per the FSM and all the cumulative experience with these transmissions. The problem is it might just give up at an inopportune time because of the lack of maintenance.



Modern ATF does much more than the ATF of old and is formulated quite differently. The additives that make it so good and keep the seals, frictions, etc, in good shape are highly volatile. They disappear every time the trasnmissions warms and cools. Eventually they are either gone or at levels lower than needed.



ATF not only provides the driving medium and cooling but is also responsible for cleaning and conditioning. It has the ability to supend and encapsulate harmful contmainants, to a point. Beyond a certain saturation point it cannot do its job and wear will occur on seals, frictions, metal parts, etc.



Simply put, the benefits of a fluid exchange every 30k far outweight cost and to simple to ignore. If a fluid exchange causes issues to show, it was only a matter of time until they would show anyway.