Sequence for trans fluid service - pan drop or

[ford46guy]

Originally Posted By: nobb
I was tempted to get a Dorman pan with the drain plug, but IMO I think spending the extra time to drop the pan is worth it. You'll not only get at slightly more fluid, but it also gives you a chance to clean off the magnetic sludge that is left which is what often causes the various solenoids in the transmission to short out and fail.


In my case my pans are rusted out and may be weeping, or soon to be, so new pans may be required.
Also, the plug makes it easy to drain the oil so you can remove the pan without a bath if you don't have a lift.

Laying under a car with a pan full of fluid is no fun. I guess you can pump out fluid thru the cooler but the pan is really easy.

 

[Trav]

When you drop the filter fluid from the valve body is coming out, when you fill it start the engine and leave it in park and the pump will draw the new fluid up, don't shift it through the gears until all the old fluid has been exchanged.
Any fluid that is in the small passages of the valve body and solenoids will go out through the pump not drop back in the pan.
There may be a small amount of mixing somewhere in the system but its so minimal its not worth talking about and harmless.

 

[slacktide_bitog]

Originally Posted By: nobb
I was tempted to get a Dorman pan with the drain plug, but IMO I think spending the extra time to drop the pan is worth it. You'll not only get at slightly more fluid, but it also gives you a chance to clean off the magnetic sludge that is left which is what often causes the various solenoids in the transmission to short out and fail.


Get a magnetic drain plug then. You still get to clean off the magnetic sludge without having to remove the pan, plus you'll change the fluid more often since it is so easy with the drain plug

 

[DeafBrad]

I would suggest you drop the pan first as you will use less atf. If you flush it out and then drop the pan you will be draining out some of the new fluid you just put in. Then you will need to top off the system after you re-install the pan. For my van that would be 4 quarts, and 4 quarts can add up in price.

In my mind, flushing is good. I did what was almost 3 pan drop and fills, and the fluid was still nasty dark. I finally ended up taking the return line off of the transmission and flushing it out. Now the fluid is beautiful.

 

[alcyon]

Is it a must to drop the pan to change auto transmission fluid ? Sorry, I have never owned an auto trans car.

 

[Trav]

Its best to drop the pan if there is one. You can change the filter and clean the junk out of the pan prevent it from getting in the new filter.
Some transmissions don't have a pan so with these its not an option.

 

[ford46guy]

Did it on the Explorer below earlier:
1) Let out 2 quarts from the cooler
2) Dropped pan, still got a bit of a fluid bath (no lift)
3) Cleaned magnet (pan flange is rusted, leaky, replaced with Dorman w/drain, Excellent fit, could have been a Ford part).
Magnet had a fine toner like black powder on it. Fluid was starting to get darker, old pan had this residue too.
4) Installed new Motorcraft filter kit, with cork/rubber gasket that came with filter (old flat rubber gasket may have been reusable, but had rust buildup). Tightened pan bolts to spec, about 130 inch/lbs, went over them twice.
5) Put back about 4 quarts, pumped a quart at time out the cooler and replaced (2 quarts were starting to pull air).

Trans holds 9.5, used 13 qts to flush.

Used Motorcraft Mercon V, got a great price. Shifts better than a new trans now, drove about 100 miles already.
I couldn't find a magnetic drain plug, but there is a pan magnet. Would it make sense to have both magnets?

Now I can easily replace fluid every other oil change.

 

[zzyzzx]

Originally Posted By: KrisZ
The sequence is irrelevant and is a matter of personal preference.


Possibly so, but I figured the way I did it, by changing out the fluid first, if it freed up anything that ended up in the filter, I would get that when I changed the filter since I was doing that part last.

 

[Trav]

Sounds like you got the job done right and doing it yourself you took care, something a lot of places don't do.