4R100 Flush Procedure

By Mark Kovalsky (as posted on FTE)

I've done this alone. It's easier with a second person, and sometimes helps prevent spills.

1. Things you need to get started:
   1. The E4OD and 4R100 transmission system holds almost 18 quarts of ATF, and you must waste a couple of quarts to be sure you get it all purged and replaced, so buy 20 quarts of MERCON ATF [For the 4R100, use MERCON V]. You may use either conventional or synthetic, as long as it meets the above requirements.

The 4R70W transmission system holds about 14 quarts of ATF. The 4R70W uses MERCON V, and the MERCON V can be used on older 4R70W transmissions that were factory filled with MERCON.

1. I replace the transmission filter every other fluid change. Note that Ford does not recommend ever changing the filter. I've opened filters with over 300,000 miles that were not even close to being clogged.
2. Don't buy a new pan gasket. The original is reusable.
3. A 10 foot length of clear tubing and one hose clamp, sized to fit over your cooler hose. There have been different size cooler lines over the years, so check before buying!
4. If you don't already have a special funnel that fits into the transmission dipstick tube, then you will need one of those, too.
1. If you are changing the filter, drain the pan if your pan has a drain plug. If you are not changing the filter, jump to step 4.
   1. If you don't have a drain plug, go to step 4 to pump out the pan, preventing an ATF shower! Return here after step 4 and one pass through step 5a.
   2. Remove the pan and clean the pan and gasket, including the magnet on the bottom of the pan. Fuzz on the magnet is normal, that's why it is there!
   3. Change the filter. It just pulls out, there are no bolts that hold it. It is held in place by the pan. Make sure that the O-ring is removed, too. Sometimes it does not come out with the filter.
   4. Replace the pan, using the reusable gasket.
   5. At this point you can drain the torque converter. Some people think it is necessary, but I don't. Running the engine in the next steps will pump the fluid out of the torque converter. If your transmission was built after August 2001, you don't have a drain plug in the torque converter.
   6. To drain the torque converter remove the shield (or the rubber plug in some models) and turn the flywheel until you see the drain plug. If you also drain the torque converter, then the old ATF will not come out the return line until after the torque converter has filled.
2. If you drained the pan, pour new ATF into the filler [dipstick] tube until you have added about as much as you earlier drained from the pan. At this point overfilling by no more than one quart won't hurt anything.
3. Disconnect the transmission-fluid return line at the transmission - from where the ATF returns to the transmission from the cooler. This is the line towards the rear of the transmission. Clamp the clear tubing over the line that you removed from the transmission. This is where the fluid comes out.
4. This is where the second person comes in handy. One person starts the engine, while the other holds the line over the drain bucket. A clothes pin can replace the person holding the line in the bucket.
   1. Run the engine until you see some air in the clear tubing. As soon as you see air shut off the engine. Refill through the dipstick tube with the same amount as you just pumped out.

NOTE: If you drained the pan and the torque converter, fluid will not run out until you fill the pan a second time. Run the engine for 30 seconds, then stop and add six more quarts.

1. Repeat step 5 until you have added 19 quarts with of new ATF to the system with an E4OD or 4R100. Repeat until you have added 13 quarts with the 4R70W.
   1. At least one time while the engine is running move the shifter through each position from P to 1, pausing about 5 seconds at each position. This will change some fluid that would otherwise be trapped in the valve body, accumulators, and clutches.
2. Remove the clear line and reconnect the cooler line to the transmission.
3. Check the fluid level and use the last quart to top off.
4. Properly dispose of the used transmission fluid.
5. Congratulate yourself! And your engine starter/killer person.