Transmission fluid replacement

By Dominic Vautier

My son has a 2000 Escort zx2.  He had about 100,000 miles on his automatic transmission without a fluid change,  When I drove the car I immediately noticed how slow the car changed gears so I purchased a new filter and gasket.  Those automatic units need to get a change every 30,000 or so.

I looked up the replacement type and volume.  All sources of information I found were consistent: four quarts of Mercon 5.  These sources included salesmen from 2 different parts stores, the web and two different maintenance manuals.


I encountered some difficulty removing the pan on those Escorts because it is impossible to get at all the pan bolts, especially with a car from Michigan where a lot of salt is used on the roads during winter and everything is rusty.  A brace supports the front motor mount and it blocks access to several of the pan bolts.  So I found it completely necessary to drop that brace while supporting the front motor mount with a jack.  In addition the brace is also blocked by another brace that runs laterally and supports the lower wheel control arms. With that done I had clear access to all the pan bolts and was able to drop the pan.


When I drained the pan I was surprised at how little of the old oil was there.  I replaced the filter and gasket and refilled the transmission with new oil.  To my astonishment I found out that the transmission needed only two quarts or so of Mercon 5, not four quarts as all the books and people had told me.  So I had to remove the engine braces and pan bolts, and drain out around two quarts of excess oil.  Needless to say I was quite upset.  The moral of this story is to measure what you take out so you can put an equal quantity of new stuff back in.  Maybe another moral is that the technical writers don't always know how to write technical manuals.  

I tried to find out why everybody was wrong.  Some people said that the books are wrong because they refer to a complete overhaul in which case you do need four quarts of fluid.  I was unable to find anybody who could give me a good reason why all the books and service people are unable to tell me how much transmission oil is needed to change the transmission fluid.