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Changing ATF: 7.3L PowerStroke Engine and 4R100 Automatic Transmission.

576K views 151 replies 50 participants last post by  Mark Kovalsky 
#1 · (Edited by Moderator)
This procedure replaces the outdated FAQs now accessed off the home page.

Note: This article was revised on May 2, 2008. It was first written by Mark Kovalsky several years ago, so "I" in the procedures is Mark, not Smokey. :thumbsup:

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Transmission Maintenance - Do It Yourself (DIY)

Changing automatic transmission fluid (ATF) in a SuperDuty truck with 7.3L engine and 4R100 automatic transmission. (Will also work on earlier trucks with E40D transmission.)

NOTE: THIS WILL NOT WORK FOR A TORQSHIFT TRANSMISSION. It is not valid for any transmission newer than the 4R100.

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

1. Things you need to get started:

a. The 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 V ATF. You may use either conventional or synthetic ATF, as long as it is rated MERCON or MERCON V. Your Owner’s Guide says to not use MERCON V, but Ford changed that in 2006.

b. A 10 foot length of clear tubing and one hose clamp, sized to fit over your cooler line. There have been different size cooler lines over the years, so check before buying! The metal part of your cooler return line is probably 3/8th inch outside diameter (OD) with a ferule on the end of it, so if you can find 7/16th inch inside diameter (ID) tubing, that will probably work great. If you use ½” ID, it will be a loose fit over the ferule and will need a good hose clamp tightened good to prevent it from leaking. So just in case, place a big drain pan under the connection. And some folks have reported they were strong enough to force a 3/8th inch ID tube over the ferule. If you try that, dipping the end of the plastic tubing in very hot water for a few seconds will make the job easier.

c. If you don't already have a special funnel that fits into the transmission dipstick tube, then you will need one of those, too.

d. If your transmission has ever been worked on by a Ford dealer, you probably have a Magnefine in-line filter in the "rubber" part of the cooler return line, near the front axle. If so, you should replace that filter every time you change the ATF. You can get one from your Ford dealer, or for about $15 from Magnefine Filters--Online Order Form. Your cooler lines are probably 3/8th inch, so you want the 3/8th size Magnefine inline filter.

2. Note: In cool or cold weather, be sure the transmission is up to operating temp before you begin. It’s not supposed to happen, but several members have reported ATF coming out the cooler bypass line instead of the cooler return line if they tried these procedures with a cold transmission. Also, in cool or cold weather, keep the new ATF in the house so it’s around room temperature of about 70º F. when you pour it in the transmission.

3. If your pan has a drain plug, drain the pan, then replace and tighten the drain plug. If it doesn't have a drain plug, skip to step #5.

4. Pour 7 quarts of new ATF into the filler [dipstick] tube.

5. Disconnect the transmission-fluid return line at the transmission - from where the ATF returns to the transmission from the cooler(s). This is the line towards the rear of the transmission. This is where the old ATF from the transmission, torque converter and coolers will be pumped out. Clamp the clear tubing over the line that you removed from the transmission.


The following is a drawing of the 4R100 transmission, seen from the passenger’s side of the vehicle. The arrow at #2 shows the banjo connection where the cooler return line and the cooler bypass line connect to the rear of the transmission. The arrow at #4 shows where the “hot” line and the cooler bypass line comes out of the banjo connection on the front of the transmission. (The cooler bypass valve is near the banjo connection at the front of the transmission, in that bypass line that runs between arrows #4 and #2.)



6. 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.

a. Run the engine at idle RPM until you have around 1.5 gallons in the drain bucket, then you should see a big air bubble in the clear tubing. Ignore tiny bubbles. As soon as you see a big air bubble, shut off the engine. Then double-check the amount of used ATF in the drain bucket. You should have around 1.5 gallons. If you have much less than 1.5 gallons, then you probably killed the engine too soon, so crank the engine and pump out some more old ATF.

b. If you drained the pan in step 3 and poured in 7 quarts of new ATF in step 4, then while the engine is idling in step 6a above, 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.

c. If you poured in 7 quarts of new ATF in an earlier step, then refill through the dipstick tube with 6 quarts of new ATF. (That's 13 quarts total so far). If you have not poured in any new ATF yet, then pour in 7 quarts of new ATF, for a total of 7 quarts so far.


7. Repeat steps 6a and 6c until you have poured in a total of 19 quarts of new ATF (7 + 6 + 6).


8. Remove the clear line and reconnect the cooler line to the transmission with 20 lb/ft torque.

9. Drive the truck several miles to get the transmission up to operating temperature. Then check the fluid level and use the last quart of ATF to top off.

Note: You should always check the ATF level when the transmission is up to operating temp – not when it’s cold. The cold marks on the dipstick are not very reliable. When first filling the transmission, use the cold zone on the dipstick to get close to the right amount of ATF in the transmission. But for topping off, do it with a hot transmission using the hot area of the dipstick. When you get done, you want the transmission full, but not overfull.

10. Properly dispose of the used transmission fluid.

11. Congratulate yourself! And your engine starter/killer person.

12. Then get back on TheDieselStop and tell us your "lessons learned" for those that follow you down the DIY road.

Now that we understand the basic procedure, let's muddy the water with the options:

Optional: Change the internal transmission filter. Revise paragraph 3 above to read:

3. Drain the pan, remove the pan, replace the transmission filter, clean the inside of the pan and clean the reuseable gasket, install the pan, then replace and tighten the drain plug. Torque pan bolts to 11 lb/ft.

If your pan doesn't have a drain plug, you remove and drain the pan at the same time. This might be a messy job, but most tranny pans on other vehicles don't have a drain plug, so you won't be doing something the pros don't do routinely.

Don't buy a new pan gasket. The original is reusable.

The pans for the 4x2 and 4x4 drivetrains are slightly different, so the internal transmission filter is also slightly different. So be sure you buy the correct transmission filter for your drivetrain.

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.

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.

Optional: Drain the torque converter. Add the following to paragraph 3 above:

If your truck was built before August, 2001, then you may have a drain plug in the torque converter. If you do, then you can also drain the torque converter as part of step 3 above. 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.

If your torque converter does include a drain plug, then to drain the torque converter remove the shield (but NOT the upper right bolt - this one only needs to be loosened) and turn the flywheel until you see the drain plug. If you drain the torque converter, be sure to replace the drain plug, and torque it to 18 to 20 lb/ft before you continue.

If you drain the torque converter, then the old ATF won't come out of the end of the cooler return line until the torque converter is filled with ATF. So instead of waiting until you see big air bubbles in the drain line during your first iteration of going through in step 6a, run the engine for about 30 seconds while changing gears for step 6b, then cut off the engine.

Optional: Blow out the coolers. Add the following to paragraph 5 above.

It's not necessary, but some folks want to get every possible drop of the old ATF out of the system before they pump new ATF through the system. If you drained the torque converter, then you might also want to blow the ATF out of the coolers and cooler lines. If you have an air compressor, you can reduce the line pressure to about 15 PSI, remove the cooler "hot" line from the front of the transmission, and blow air into that line. That will force the ATF in the coolers and lines out the cooler return line at the back of the transmission. DO NOT use air pressure of more than about 15 PSI! Then be sure to reconnect that line before you continue with paragraph 6.
 
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#33 ·
I have a powerstroke 7.3 Yr 2000
Has 318800 miles.AT I have heard you can damage the transmission if you change the fluid,because the detergent will wear whats left of plates and cause breakdown. What is your take and what would you do if it was your truck. It is all Highway miles towing a #13000 5th wheel
 
#35 ·
What is your take and what would you do if it was your truck. It is all Highway miles towing a #13000 5th wheel
The rumor that changing the ATF might harm the 4R100 tranny is a bunch of horse hockey. Fresh ATF is not going to hurt a 4R100 tranny. If it were mine, I'd change the ATF immediately, using Mark's procedures, and 20 quarts of Mobil 1 ATF.
 
#34 ·
Have you never changed the ATF?
Some say that not changing is more damaging, but then there is the others that say changing will have it go south.
We change engine oil and the coolant, why not ATF every x miles?
 
#39 ·
trans filter problem

Yesterday at Carquest I bought a 96050 deep pan filter for my 1999 f250 7.3 transmission. The filter I removed was for a deep pan, but a paper in the box showed a picture with a short length filter for 2wd, long for 4wd. I Measured how much the pick-up tube hung down(4 inches+-), the depth of the pan-Right filter? Does the tube support the filter flat on the pan bottom? I installed the filter-(tube in hole) the filter just hung there at an angle, it didn't fasten in at the other end. I centered the filter where a trans screw lined when held up, but fear the filter could get moved over when I put up the pan? Any thoughts? Thanks
 
#43 ·
If the oil is overfilled it can get whipped into foam by the crankshaft. Foamed oil can't lubricate, so you'll have metal to metal wear and if that gets bad enough you'll need a new engine. I don't know how much overfilled is too much. I never fill an engine all the way to the top of the full mark.
 
#44 ·
Flushed it! Just completed the flush via the Mark Kovalsky / SmokeyWren Way. Excellent results. Worked just as they said it would. Dropped the pan and replaced the screen/filter. Used M1 Synthetic. Clear tubing was the just the ticket. My dad was the bucket and hose man while I started the engine. Flushing the transmission in the barn with my dad and being by the warmth of the wood stove made it all the better! Thanks for your expert advise and for saving all of us a lot of guesswork.
 
#45 ·
Did mine this past Sunday, per the instructions, and with a filter change. Used the Mobil 1 Synthetic. With the wife in the cab, and me doing the rest...start to finish was about an hour.

Very easy. I wish I had back all that money I spent paying someone else to do it these past 10 years.
 
#46 ·
Noob here to the 99 + side have had and IDI for about a year but just picked up a early 99 a few days ago. It has 340,000 on it and auto tranny started acting up yesterday somewhat like post #28 by zoomzx10r posted, when put in R or D it lags for a few seconds and then goes. And then today it was slipping, pushed on the skinny pedal and not the response I was used to. I immediatly (was 100 yards from AP store) pulled in and found she was low on fluid. So put about a gallon in and now is not slipping but still get a bit of lag when intially putting in gear. I have no history on this truck whatsoever so was planning on going through it front to rear.

My question... I will do a filter change per directions in this thread but should I stick with dino oil since my AT is probably on its last leg, or use synthetic to get me a little further along?
Is there anyway to tell if tranny is rebuilt?
Thanks a million
 
#47 ·
Synthetic is only going to help if you do a lot of towing and frequently get the trans hot. In normal use there isn't much advantage to synthetic.
 
#48 ·
I did this last night. I only had 4 of the 5 gallons so I didn't get to finish. 5th is in the mail so hopefully be here today.

One helpful tip I would like to add, if you have a Tru-Kool transmission cooler you will not need to remove the return line at the transmission. I was able to use the line that was spliced in for the trans cooler in the front that goes from the return line to the cooler. The fluid comes out of the line going to the cooler so that is the one you place in the bucket. Just undo the hose clamp and pull the cooler line off. I was able to actually just drain it back into the empty trans fluid containers and could tell when it was 1.5 gallons easily. I did have some leakage out of the other part but it was probably just dripping from what was in the line.
 
#49 ·
Were you getting just some dribble out of the other line, or a small steady stream? The first would be fluid in the line, the second would indicate a problem with the cooler bypass, a problem that is easy to detect if you remove the line at the rear of the trans, which is why I wrote the procedure the way I did.
 
#50 ·
Dribble. Wasn't a constant dribble. Just enough to drip onto the radiator hose and run a little. I had to drain out of the line a second time after reattaching though because I misread something and had to drain another 1.5 quarts out. It didn't drip anything out that time.
 
#51 ·
In the Beginning of this thread in was noted that Mercon V was acceptable now in the 4R100 transmission, my question is, I did the transmission flush as noted several 1000 miles ago, and now time for another flush, I still have several left over quarts (over 1/2 case) of the Mercon, is it OK to buy Mercon V and combine the two, or NOT, I really don't want to waste it at over $6 a qt.

Thank you again for a fantastic write up, it worked so well.
 
#55 ·
Not at all wise. The oil-to-water (OTW) cooler does most of the work under extreme conditions, and the oil-to-air (OTA) cooler is an auxiliary. As long as you have ATF flow back into the tranny after the coolers of at least one quart in 15 seconds (one GPM) then don't worry about it.
 
#54 ·
No. The OTW is the most efficient part of the cooling stack and has little resistance. Do not bypass it.


Sent from AutoGuide.com App
 
#57 ·
Bypass filter? You can't plumb that directly into this circuit. Bypass filters have restrictors that would wipe out flow. You need a Magnefine or nothing.


Sent from AutoGuide.com App
 
#59 ·
Good info
 
#60 ·
Installing 6.0L cooler at same time

I am just about ready to replace my fluid, and have a new 6.0L cooler. I have installed a spin-on baldwin filter per Woodnthings method, and am wondering the best process to get as much fluid out as possible. Spin on mounted, but not actually connected yet.... was going to do all at once.

Should I drain pain, then disconnect hot and return line and blow 10psi air through to get everything out of the lines, then install new 6.0L cooler and new spin-on filter, clean pan, replace in tranny filter and then fill?

TimK
 
#61 ·
No - go up to post #1 on this thread and read Smokey's ATF change procedure.
 
#62 · (Edited)
6.0L cooler as well

So would I replace the cooler first, then follow the procedures?
I would assume if I do that, and install the spin on filter that it would put air bubbles in the system, so it might not go as planned (air bubbles in line as described).
I guess if I just watched the amount of fluid coming out of the return line (plus checking color) then I would essential push the old out while installing the new.

Timk
 
#63 ·
You don't have to worry about air in the system - the system flows fast enough that any introduced air will work itself out within a minute of idling. You can replace the cooler first or after - your choice.
 
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