ATF change procedure

[bononos]

I'd like to know the procedure to flush out the AT fluid by the drain and fill method several times. How far should I drive to get the undrained fluid in the other parts of the AT to flow out and around to where I can drain it out. Like a block or 2? Would that be an appropriate procedure for an Accord and Japanese subcompacts?

 

[Jimzz]

Why do you think you need a "flush"?

Just do a drain and fill and drive till the next oil change. If the fluid still looks bad then do it again.

Use fluid that meets honda spec like Valvoline maxlife. Don't use regular Dex3 or any other fluid that does not say it meets Honda spec.

 

[silicon]

I'd like to know the procedure to flush out the AT fluid by the drain and fill method several times. How far should I drive to get the undrained fluid in the other parts of the AT to flow out and around to where I can drain it out. Like a block or 2? Would that be an appropriate procedure for an Accord and Japanese subcompacts?

What is the mileage of the vehicle? Does the fluid look black or smell burnt? In general those transmission need the pan dropped to change the filter if there is a filter to be changed. Also in the bottom of the pan is a magnet, i think, that collects the metal particles. I owuld say just completely drain the fluid, change filter and replace the fluid.

 

[BUTCH1]

What is the mileage of the vehicle? Does the fluid look black or smell burnt? In general those transmission need the pan dropped to change the filter if there is a filter to be changed. Also in the bottom of the pan is a magnet, i think, that collects the metal particles. I owuld say just completely drain the fluid, change filter and replace the fluid.

Also, while it's off clean the pan bottom with something like brake cleaner, there will be some fine material on a 50-60,000 mile tranny, remove and clean the magnet as well then wipe down with a lint-less towel (a small micro-fiber one works well). I simply re-used my original gasket as the replacement one looked flimsy as hell, while you may not get all the old fluid out you getting 75% of it out and I for one do not like the idea of "flushing" the tranny as it could wind up moving the sediment into the valve body and that's asking for trouble IMHO..

 

[deadken]

While I'm not against flushing a transmission, I don't think it is always called for. The last transmission I flushed was on a Volvo 940 Turbo (the transmission fluid was definitely 'cooked'). I've done just regular changes on different cars since then.

AFTER changing the filter, I can just refill the transmission and ASSESS whether or not I still think it needs a flush. If it does, then I'll open 6-9 quarts of fluid, and get a section of fuel hose, a funnel, and a bucket.

1) Remove a transmission cooler line from the radiator, attach the fuel hose to it and put the other end in the bucket. Put a drain pan under the radiator and start the car. After 2-3 seconds turn off the car and see that transmission fluid is going into the bucket. If it is coming out of the radiator and into the drain pan, then I have chosen the wrong transmission cooler line (the return instead of the feed). So, I'll put back that transmission cooler line and remove the other one, put the hose on it, and put the hose in the bucket. Try to position the bucket so that you can see it while you are filling the transmission with fresh fluid.

2) Remove the dipstick, insert the funnel, and set the open quarts of fluid so that they are easy to reach (but not easy to knock over).

3) Start the engine again pour in the fresh fluid as the old fluid pumps out. Please note that the cooler lines don't have a lot of pressure and at idle don't have a lot of flow. Watch how fast the fluid is pumping out of the transmission and continually add new fluid. Try and pace yourself to not overfill the transmission.

4) As you watch, you will see the color of the fluid coming out of the hose get cleaner and cleaner. When you are happy with how it looks compared to the new fluid you are adding, turn off the engine.

5) Reconnect the transmission cooler hose to the radiator.

6) Fill the transmission to the proper fill height.

FWIW: I usually buy a case of transmission fluid when I buy the filter and gasket. I might use 3 or 4 quarts to fill the transmission after the filter change. If I determine that I want to flush the transmission, I will then open the remainder of the quarts. The fluid doesn't come out so fast that I'm in a panic about not keeping up, but I do like having the tops off of the bottles to keep things moving smoothly. If you want perfectly clean transmission fluid (what we used to call 'cherry cough syrup'), you might want to flush with 15-18 quarts of fluid. I find that a case of 12 usually gets the fluid clean. Not perfect, but clean.

 

[bononos]

The transmission is fine and isn't due for a filter change yet. I just want to change more of the fluid than just a simple drain and fill. Driving it would push the some of the old fluid from the cooling tubes and whatever else that wasn't drained yet so I just wanted to know how far to drive (also means how fast the fluid circulates).

.......
3) Start the engine again pour in the fresh fluid as the old fluid pumps out. Please note that the cooler lines don't have a lot of pressure and at idle don't have a lot of flow. Watch how fast the fluid is pumping out of the transmission and continually add new fluid. Try and pace yourself to not overfill the transmission.
........

I might try that if it doesn't look too fiddly.

 

[phucheneh]

The complex driveway 'flush' procedures that you'll see people doing on enthusiast forums are useless. Just a waste of time and materials.

If you feel changing, say, 5qts of fluid in a system with a dry capacity of 9qts, is not adequate...change the fluid more often. Makes a hell of a lot more sense that trying to change 5/9ths of the fluid...then immediately doing it again to throw out 5/9ths of that new five quarts in order to change out 5/9ths of the remaining 4/9ths of old fluid...ect, ect; the fractions only sound sillier as you get into the third drain that I've seen people do...

There is no need for your transmission to be squeaky-clean inside, and the people who do this super-wasteful stuff to try and satisfy their OCD would be much better served by simply changing the fluid more often. Between doing a drain and fill every 30k, and doing a whole pile of drain and fills every 50k...I would recommend the former.

Trying to actually do a 'flush' by disconnecting a cooler line and manually filling the trans with the engine running is outright retarded. Ignoring some obvious reasons why I would never bother trying to do that (you know, like, not wanting to trash a transmission)...you're using the same faulty logic that people use to justify flush machines.

Fluid is drawn up from the sump by the transmission's internal pump...gets pumped out into a waste container...new fluid gets dumped back into sump to mix with old fluid, and said mix and drawn back up through the pump...repeat ad nauseum, with the possibility that you could be 'replacing' twice as much fluid as a drain and fill...to ultimately accomplish the same thing. Maybe a little more. Maybe a little less. But what you're definitely NOT doing, is constantly pumping out 'old' fluid and directly replacing it with 'new' fluid.

It's basically taking the concept of a cooling system flush, and applying it to a system that does not work in the same way. Brilliant.

 

[deadken]

The complex driveway 'flush' procedures that you'll see people doing on enthusiast forums are useless. Just a waste of time and materials. ...

There is no need for your transmission to be squeaky-clean inside, and the people who do this super-wasteful stuff to try and satisfy their OCD would be much better served by simply changing the fluid more often. Between doing a drain and fill every 30k, and doing a whole pile of drain and fills every 50k...I would recommend the former.

Trying to actually do a 'flush' by disconnecting a cooler line and manually filling the trans with the engine running is outright retarded. Ignoring some obvious reasons why I would never bother trying to do that (you know, like, not wanting to trash a transmission)...you're using the same faulty logic that people use to justify flush machines. ...

As a guy who likes European cars, I am a fan of regular maintenance instead of neglect and catch up. But, as a guy who buys used cars, I sometimes have the need to play catch up.

The 'driveway' transmission flush procedure really isn't complicated. I agree that the fluid doesn't need to be pristine. In my post I even pointed out that changing the filter and topping off might be just fine. I don't usually waste the extra product required to get it 'perfect' and I don't advocate others doing so. Clean and fresh are just fine. That being said, if a guy wants to use the entire case he bought, it's his decision.

Ummm... If you don't want to do a 'driveway' flush, it's fine and your decision. If you think that you are going to 'trash a transmission', then I suspect you really don't know what you are talking about. Again, it's fine to just do a regular change and another sooner rather than later. But, to suggest that you'll trash the transmission by doing a flush is just silly.