How-To: Changing 4x4 Transfer Case Fluid

[arco777]

How to change your Transfer Case Fluid - 91-94 Explorer 4WD

You will need the following at a minimum:
-2qts Mercon Automatic Transmission Fluid or equivalent
-3/8" ratchet (may need a breaker bar)
-13mm socket
-Oil drain pan
-Paper towels/rags
-Fluid pump (see picture)

You may want to jack up the vehicle slightly to have more room underneath to work. Always use jack stands and be safe.

Pictured:
One gallon bottle Dex/Merc ($18), one fluid transfer pump with lifetime warranty ($10). This fluid pump is really handy and works great for pumping gear oil into differentials too.

 

[arco777]

First you'll need to remove the harmonic damper to access the drain plug. Look under your car on the driver's side, rearward of the transfer case skidplate. You should see the damper, with four bolts holding it on. In the pictures, a couple of the bolts are already loosened. You'll need a 13mm socket for the bolts. The damper is weighty so don't drop it on your head.

 

[arco777]

Once the damper is off, note which direction it was on. I believe it can go on either way, but just in case, I noticed on mine that the lettering stamped into it was on the transfer case side (facing inwards).

 

[arco777]

Now you have access to the drain plug. In the picture, the red arrow shows the drain plug. The green arrow shows the fill/check plug.

To remove these plugs, unscrew them by inserting a 3/8" square drive into them. You may need to use a breaker bar.

Remove the drain plug. Have an oil drain pan ready under the vehicle, as fluid will pour out. It may land on the skidplate so be ready for it or put a small funnel under the plug to catch the stream and direct it into the drain pan.

 

[arco777]

Hopefully the fluid that comes out of your transfer case won't look this black.

 

[arco777]

Clean up the drain plug. It may or may not be magnetized. If it is, you'll probably see some metal filings and metallic sludge on it. Hopefully no chunks.

Clean the hole out. You don't want any gunk in the plug threads.

Note that there is a gear or something right behind the drain plug, so don't go putting a longer drain plug in, like one with a magnet on the end. You could magnetize the stock drain plug, though.

 

[arco777]

Put the drain plug back in. Just snug it down, don't crank on it! Now remove the fill plug.

 

[arco777]

Attach the fluid pump to your ATF bottle, put the output hose into the fill hole on the transfer case, and start pumping. It will take quite a few pumps... I quit counting at 50.

You want to fill the transfer case until fluid starts to run out the fill hole. Be careful because if you squirt fluid in against the gear that's just inside the hole, it can splash back out the hole and make you think it's full. So route the output hose a little farther inside the case. Pump until fluid starts to run out. Then put your finger in the hole and feel if the fluid level is up to the bottom of the fill hole. That's where it's supposed to be and when you check it later it should be topped off to that point.

When the transfer case is properly filled, re-install the fill plug. Again, don't put it in too tightly, just snug. Also make sure the plug and the hole are clean with no gunk in the threads.

 

[arco777]

Double check your work, that you didn't leave either plug loose.

Finally, re-install the damper with the four bolts. These need to be fairly tight. A standard 3/8" ratchet will provide all the torque you need on these; you don't need a breaker bar or cheater pipe or anything. You can use some low or medium strength threadlock if desired.

You're done! At some point after you test drive it, check that there are no leaks.

 

[willindsay]

Good Write Up.

Just a suggestion though I would take the fill plug out before the drain plug because it would suck to get all the fluid drained only to figure out the fill plug won't budge. You'd be stuck with an immovable vehicle.

Also the weight isn't really needed I left mine off the last time I checked my fluid.(which reminds me it's time to check it again)

 

[RangerX]

Nice writeup! Where did you get the fluid transfer pump?

 

[corkey]

the pump is available at any marine dealer, they are usually used for lower unit oil, or gearcase oil ,

 

[arco777]

Nice writeup! Where did you get the fluid transfer pump?

I picked it up at O'Reilly's for $9.99. It's really handy. The construction is not the strongest but out of three I've had, I only broke one and the store replaced it under the lifetime warranty.

Also the weight isn't really needed I left mine off the last time I checked my fluid.(which reminds me it's time to check it again)

That may be so. I imagine it is similar to the damper weight on the 8.8 rear axle on Fox Mustangs. Some people say it's just excess weight, some say it makes a difference. I figure if Ford cared enough to make it and put it on, it must be for a reason.

 

[Bruces expo]

Great Write Up and Good pics as Well ! .

 

[Champcar_Fan]

Thanks - nice writeup. I'll do it at the same time when I'm working on the shift motor.

 

[91 Sport 90K 94 XLT 157K]

Excellent writeup , now i got something to do when spring comes around

 

[IAmTodd]

Great write-up!

Just a suggestion though I would take the fill plug out before the drain plug because it would suck to get all the fluid drained only to figure out the fill plug won't budge. You'd be stuck with an immovable vehicle.

I completely agree with always removing the fill plug first regardless of what you're working on.