Please note: this applies to the 1st generation (1997 to 2002) Ford Expedition

This is my first write up here on the boards and I hope new users will find this beneficial and use this guide as a reference.

First and foremost this is an EASY task to complete. On a 10 scale, this is a 2. The only difficult part is getting the fluid back in the transfer case after draining the transmission fluid. I didn't have anyone to take photos of me refilling the transfer case as my hands were pretty filthy as I was finishing the job so I hope three photos are enough.

Tools & Materials needed:
3/8 Ratchet
Various 3/8 extensions to access
Teflon tape
Pump - for pumping the transmission fluid back into fill hole
2 qts Mercon or Mercon V ATF
Catch pan to drain old ATF in




First, this is the Borg Warner 4406-12 transfer case. I'm not sure if this changed at all through the years (when Ford went from A4WD/4H/4L option to just 4H/4L) but this is the model on my '97. You access the transfer case from the drivers side of the vehicle. It is located on the left side (driver's side) of the transmission. The fill and drain plugs are on the back side (facing the crossmember) of the transfer case.

I couldn't get a good photo of the drain and fill plugs but it's obvious what they are when you look on the transfer case. It is also obvious as to which plug is the drain and which is the fill point. The drain is the lower of the two meaning closer to the ground. Nothing tricky about this job - except the refill!

IMPORTANT! Before draining the ATF from the transfer case, make sure you can remove the fill plug first. You will be in a heck of a position if you cannot replace the ATF. To access the fill plug, simply reach up and place your ratchet head in the fill hole. It's a little tight with the crossmember in the way but it's not that bad. Be patient and you will be able to remove the plug. One other way to access the plug is by going over the top of the crossmember and use a long extension. Once removed, set aside and place the catch pan under the transfer case. Remove the drain plug and let the old ATF come out. Give it a couple minutes to fully drain. I actually replaced the plug enough to stop the drain, waited a minute, and then removed the plug to drain even more fluid.




These are the drain and fill plugs. Before replacing I wrapped each with 2-3 wraps of Teflon tape. I did this to ensure I wouldn't have a leak. I'm not sure if this is needed or if I should have used something else on the threads, but I did it anyway. I don't think this will have any adverse effects on the long run. Feel free to use any method you want, but this is how I did it and so far so good.

Next replace the drain plug, screwing in the plug till its flush with the transfer case body. Then using your pump, run the fill line over the top of the crossmember (otherwise the angle is pretty sharp) and start refilling the ATF. I think this job would have been easier with a second hand to help assist in this process but you can do it solo. Note, I was informed here on the boards that "Mercon V" is OK even though the manual clearly states "Mercon". From what I was told, Mercon V is the updated fluid. I used Mercon V in this change.

Now, there is no stated quantity of ATF needed for the refill. From other members posting here, your transfer case will take "almost" two quarts to refill. However, mine used two quarts exactly. You want to fill to the point just when the new fluid begins to run back out of the fill hole. Reseal the hole with the fill plug until it's flush with the transfer case body.

You are finished! Now I recommend wiping off the area around the plugs and watch for any leaks.

Lastly, this is why it is important to change the fluid:


Let's hope you know which fluid is old!


Hope this helps,
Tom

 

Nice write-up.

 

i have 122k on my 03. owned it since 69k. have yet to have the fluid changed......

 

When I did this change two weeks ago, my vehicle had 111k on it. I honestly didn't expect the fluid to be black and I was quite surprised. I changed the fluid for two reasons: 1) because I just bought this vehicle in February and have doing fluid changes as I can afford them and 2) because I looked at the service schedule on it and it was supposed to be done a while back. When I pulled that drain plug, I was thinking dark red fluid would come out to indicated this job had been done already since the owners had kept real good care of the truck. However, every fluid I have changed so far has still been good condition except this. I recommend changing your fluid after seeing how bad mine was.

 

When I changed mine I discussed the situation with the dealer. While all the TSB's about tranny fluid have switched from DEX/MERC (Mercon III) fluid to Mercon V they are NOT recommending using Mercon V in the Transfer case. In fact I think there is a TSB saying NOT to. I used no sealant on my plugs and I have no leaks. Be careful with Teflon tape.....If you use too much it will get into stuff and cause it to malfunction. I've seen 100HP hydraulic systems shut down because of a small piece of teflon tape. NEVER overlap the tape past the end of the threads!

 

There are clutches in the transfer case so when it is in automatic 4x4 and the transfer case senses rear wheel slipping it engages the front axle automatically. I changed mine 20,000 miles ago and found the fluid burnt, not as bad as yours but burnt just the same and I change my tc every 30,000 miles. This last time because of it being burnt I used Castrol MerconV as I can not find just strieght Mercon any more around here. After around 500 miles I drained it again and used M1 auto trans fluid to see if the synthetic oil would hold up better. So far the transfer case works just fine.

 

I just did my transmission again 4R100 with Mercon V for the 2nd time. No problems in the transmission at all. I was going to do the transfer case this time but the bottle says "Do not use in Transfer Cases". I am not sure what to use. The kid at the parts desk went and asked the techs and they said to use Mercon V. He told me they used to use "Mercon3" but now they use Mercon V. The bottle says don't use it and I don't think there is any such thing as "Mercon3" I think that a hybrid Dexron III/Mercon name.

GP

 

My owners manual said to use straight Mercon, check your owners manual.

 

Unfortunately Mercon is a thing of the past and there is no licensed version of it available. There are fluids that say for transmissions that used Mercon but that is not licensed or verified to be the right stuff. Mercon V is all that is available and it has been reformulated to be compatible in Mercon applications but it says on the bottle, "Do not use in Transfer Cases". I don't understand how it can be the same for use in the 4r100 but not the transfer case.

GP

 

That's funny, I just bought 2 cases of straight Mercon at Napa auto a few weeks ago.

 

I get Mercron a Wal-Mart!

 

Ford does not license anyone to make Mercon any longer. There are fluids that say "for transmissions for requiring Mercon/Dexron" but it is not Mercon fluid. I understand there is stuff available that look like it will work with no problem. Ford only licenses the Mercon V which is what the dealership is using, I asked them. I did inquire as to why the bottle says - don't use in transfer cases. The other stuff is not licensed/approved fluid. There is also apparently Motorcraft XL-12 Transfercase fluid which the dealership has no idea what I'm talking about.

GP

 

I have been using M1 in the transfer case. It is formulated for Mercon and Mercon V. It is a little pricyer? but you only need two quarts so not to bad.I will be interested after 30,000 miles how it looks if it held up better than regular trans fluid. I have asked at two Ford dealerships also with no real answers.

 

Thanks, I wound up using Dextron 111 Mercron from K-Mart, it lists the years on it and costs $5.00

 

What method do you guys use for filling your transfer case and transmission case back with atf?