You can also use the transmission pan bolt pattern to determine which one you have. This is how I determined mine.

 

I do have the E40D...

 

Then the torque converter does indeed have a drain plug. There is a little 2" black rubber plug just behid the flywheel/flexplate inspection plate that will enable you to drain it once the plug is lined up with it. I bought three 5 litre jugs(almost 16 quarts) of ATF to refill it after I drained mine and used maybe 13.5-14 litres(14.25-15 quarts) to fill

 

Ok...dumb question...do you fill through the dip stick?

 

I probably sound like a broken record to some at this point, but is it a 2wd or 4wd?

The reason I'm asking is if it's a 2wd, there are transmission drain pans you can buy around $30 with a built in drain plug. I tried the drill in drain plug and mine seeped fluid, so those have to be welded in by someone that's crafty with a welding machine for them not to leak.

Also, you can get a reusable rubber pan gasket with a steel frame for about $30.

This makes it very easy to drain and maintain in the future. All you'd have to do that that point is drain the torque converter as mentioned previously and pull the drain plug on the pan. That makes the job very easy and A LOT less messy. Especially when you have to drop the pan to replace the filter.

Just putting it out there as an option since I saw you mentioned AAMCO.

Also, my E4OD didn't take well to the bottom of the bucket extremely cheap trans fluids such as Accel Dexron III/Mercon or SuperTech Dexron III/Mercon. If you go the cheap route, you might want to go for the Multipurpose ATFs or better yet, get a name brand such as Valvoline Maxlife or Castrol High Mileage. Or Mobil 1 if you have that kind of coin to spend. I personally use Valvoline Maxlife and my truck shifted so smooth it made me downright nervous.

Also, running it for a week or 2 with a bottle of Seafoam Transtune in it before you drain it is a good way to prep it for quality fluid.

 

I've got some ford tech buddy's that swear once a high mileage vehicle gets it done unless its had it done regularly it will mess it up.. I'd never do it I've had family members and friends that have done it and it's never good.. Change filter and fluid and be done it's too big of a risk.. If your buying a newer vehicle that's different but if it hasn't been done regular you will do more harm than good

 

What harm could it possibly do? It's a hydraulic system. Changing out the fluid removes degraded fluid and refreshes detergent and lubrication qualities. It also removes contaminants and debris that could clog passages. Flushing the system simply means you are replacing all of the fluid instead of half. What benefit could there be from leaving half used fluid and half the clutch debris in the transmissions.

 

If its a transmission that hasn't been flushed regularly since new and you start flushing it at 120,000 miles flushing it can damage it and blow seals out of the transmission that the build up is holding in... I've had and seen first hand accounts to when you flush a tranny that hasn't been done regularly since low miles you will experience problems sooner or later. I never said it would hurt anything to change the fluid and filter but somebody that flushed a tranny with high miles and no idea of its previous maintanance history will end up regretting it.. Ain't my fault you obviously haven't heard of that.. Do what you want it's your trucks and you'll regret it one day lol

 

Flushing is not done with high pressure. The only reason a flushing would cause seals to fail is because they are already useless and the detergent in the new fluid removes the sediment. Therefore the same issue would occur by replacing half the fluid. The transmission creates much higher pressure than a flushing system will. By the same logic you should never change your oil. If the seals are that bad then they need replacing. Not to mention the clutches. Most of the evidence you have seen are probably failed transmissions that the operator thought a flush would fix the problem. Because they have not been serviced regularly the first time anyone found the problem was after the flush job. Again there is nothing detramental that changing all the fluid would do that changing half the fluid wouldn't. By the way what seals are failing in the torque converter? That is the fluid in dispute.

 

Obviously you know how to use google and have no experience in the subject. Guy asked opinions and I gave mine.. He can listen to the truth or your google skills