Originally Posted By: Ndx
is it necessary to use return line ?
Can IN line be used as well ? thx
No! There is no pressure on the "in" line, the fluid is being pumped via the pump in the trans thru the "out" line to the cooler.
Donald has the procedure outlined it very well. I agree, drain the trans and refill, then do the cooler line bit. You gotta figure on some wastage doing it this way, i.e. pumping out more than the actual capacity. If the entire trans hold six quarts, then 2 gallons is likely enough... assuming no mistakes of mishaps.
I disagree with the comment above that repeated drain & fills are adequate. Actually, I would say it's not ALWAYS adequate. There are two reasons to change the oil in an automatic transmission, to replace degraded oil and to remove contamination from wear, break-in, etc. A trans creates the majority of it's contamination in the first 5K miles, so if it's the first change, you want to evacuate as completely as you can to remove the maximum amount of contamination... and that's best done with a fluid exchange preceded by a drain & refill. I don't know if the Civics have that little filter (quite inadequate, really) that some of the bigger Honda cars an Minivans have, but for the most part, you have to remember that it's essentially unfiltered oil
For routine maintenance after that first complete change, if sone before the oil is severely degraded, I wouldn't argue too much against a drain & fill method.
If the fluid is really degraded, I would also point to a cooler line service to completely eliminate the old oil as much as possible.
If you plan to keep the car for many miles, I would also advise an inline trans filter... the Magnefine (Google it) being the most effective of the easy-to-install trans filters. It would mount into the "in" line wherever it's convenient and protected from heat or damage. It will extend the life of the oil as well as the trans.
