Ford Transmissions Diesel

Ford Transmissions Diesel

When should you change the transmission fluid in a 2004 Ford Super Duty Diesel pickup?

I rarely pull anything and it has mostly highway miles on it. It's a 6.0 L Diesel with an automatic transmission.

If you want your automatic trans to last, keep it from overheating and change the fluid and filter. My wife's 2002 Cavalier owners manual says its fluid never needs to be changed or even checked! In fact there is no dipstick for the auto trans! Sounds like GM wants to sell me a new car every 100,000 miles or so. I did a lot of research and found out there is a check plug under the car (of course the car has to be hot, idling in park, safely raised off the ground, and LEVEL in order to properly check the transmission fluid level. I did this by driving the front wheels up onto ramps and then lifting the rear 'axle' with a floor jack and supporting with jack stands when the car was level.
I also did the filter change and fluid flush myself: after dropping the pan and replacing the filter and cleaning/reinstalling the pan and adding a few quarts of ATF, I disconnected one of the trans cooler lines and put clear hose on it and put it in my drain pan. Then as my wife started the engine and old fluid was pumped out, I added fluid to the fill port at the approximate rate it was being pumped out. When the color of the fluid changed (or you put in the full capacity) I stopped and reconnected the cooler line and checked the fluid level. I had to let a little drain out the check plug to reach the correct level, but it worked great (a little messy).
If you don't like working on cars or have the ambition, take it to a shop with a fluid exchange machine (but insist they first drop the pan and install a new transmission filter).

As for fluid: if you'd like to know more about Amsoil synthetic ATF or the line of synthetic diesel oils available: number1synthetic.com