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Front Diff, Transfer Case, Rear Diff, How to Change Fluid

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Alrighty... I just replaced the fluid in my front diff, rear diff, and the transfer case.... and took a few pictures.

If anyone would like to see how I did it, read on.

(moderators, if this is in the wrong section, I humbly apologize)

Again, vehicle is a 2004 Escalade AWD, with 44,000 miles on it.

Before we start, let's note that I drove the front of the Escalade onto a set of ramps, and then jacked up the rear by the trailer hitch, and placed 2 jack stands under the rear area, to put the truck up in the air and level. I'm not that small, and I was able to crawl around under there with no problems.

Let's start with the front differential:


This is the drivers side of your front diff. Camera is being held near the drivers side front tire, shooting towards the passenger front tire.. looking across the front axle area, if you will.

You see two bolts there. The top one is bigger, it's a 15mm bolt. That is your FILL plug. The bottom one, the smaller one, is your DRAIN plug.


Always remove the FILL plug first, as shown here. (Don't drain it and find out the fill is stuck... that's no good.)


Fill plug is out, came out no problem. Now we remove the drain plug with a 13mm wrench. You're going to have your pan ready underneath this, because when this comes out, fluid will be draining.... the fluid will be shooting towards you a little, so factor that in your pan placement...


Fluid is draining... nice. So far, so good.


That drain plug is a magnetic plug, and hopefully you can see, there is a lot of material stuck on there....


Drain plug wiped off... lotsa stuff there. Hopefully, I did this in time. Honestly, if I had an Escalade with 25k or more miles, I would go downstairs and change that front diff fluid RIGHT NOW. Now. You're still sitting there.... get moving! Joking. Okay, moving along.... let's assume the draining is complete. Replace your drain plug, the 13mm magnetic one.


This is what we're going to use to refill the case. It's a little pumper, I have placed the correct length of hose on the pickup side, to go into a Mobil 1 75w90 bottle... I will put the long hose into the fill hole, and them pump the thing until fluid starts coming out the fill hole, indicating that the case is full to the plug hole... I've had that pump forever, I believe I initially purchased it at a marine dealer, and used it to fill up lower unit gear cases on outboard motors...


Like so. Ready to go.


Here we see I have started pumping, the fluid is flowing up the hose and into the case.

When it's full, replace the FILL bolt, the 15mm one, and you're done.

It took me around 2.5 quarts of 75w90 to fill it back up. An approximate number, there is probably some slight line loss with my long fill tube...

You're done with the front diff!! Congrats! Light a Marlboro, take a break, and get ready to move to the middle of the truck, down the centerline, behind the transmission.


Here we have the Transfer Case. This picture is shot from the rear of the truck, looking towards the front. Thus, this face of the case you are looking at faces the back of the truck. You see the two bolts there. It may not show up on the picture, but this case is actually inscribed "Drain" and "Fill". Same concept as before.

Now, you see the square holes there, and you're thinking "What size wrench is that??" Heh heh, good question.

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Okay, we were wondering what size that bolt is....

Now, you see the square holes there, and you're thinking "What size wrench is that??" Heh heh, good question.


There's your standard 3/8ths inch socket wrench, with no socket on it. Guess what?? That's the right size square.


Like so. Note that's the drain bolt... we're going to do the fill bolt first, as always.


Fill bolt is out. Case was really full, some came out. I was told at the Cadillac Dealer that that case is full of Auto-Trak II, the blue stuff. Which is $16 a quart. The factory fill, as you can see here, is ATF, Dexron III. So, save yourself some big cash, and just refill it with Dexron III (or Dexron VI) at a far lower price.

This is thinner fluid, so it will really gush when you pull the drain bolt, and it will be coming AT you, so watch it, and watch your pan placement, unless you want a faceful....

I'm sure you've got the idea here, Pull the drain bolt, let it drain, replace the drain bolt, set up your pumper, fill thru the fill hole until it comes out, replace fill bolt... These 2 bolts, like the front diff, came in & out with no problem.

This case took about 1.5 quarts to refill....

Pat yourself on the back, you have now completed 2 of the three cases!!

I've hit the picture limit, seperate post for the rear diff....

If there are mistakes here, I'm sure smarter people than me will point them out. You can save a pile of money here, with some easy work. Hope this helps someone... enjoy.

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Okay, this is a continuation of the "Front Diff and Transfer case" Thread.... Review that one to see some of my methodology, my pump, and some details...


This is the Fill Plug on your Rear Diff. Looks rusty. This is going to be fun. This picture is looking from the passenger side rear tire, across the truck, towards the driver's side rear tire.

This is another square plug, so again, use your 3/8ths drive to remove that...


Thru the magic of photography, the plug is out. What you missed were about 5 soakings with PB Blaster (all the wet stuff on the side of the diff), then some torching with a MAPP Gas torch, and then the bolt came out. Piece of cake, right?? Right...

Now, there is no drain plug on this case.

Now, this might not be "According to Hoyle", okay, so my apologies to real technicians out there... but I was shown this years ago by a friend, and if you're patient, and careful, it will work.


This is the backside of that rear diff. That bowling-ball shaped rear cover plate is held on with bolts all the way around. The bottom 5 are visible in this photo.

If you loosen (do not remove) the bottom 7 bolts, and then very carefully and gently pry at the bottom, the case will open a little.. and fluid will drain.

You do not want to jamb the screwdriver way in there. You're just cracking it open a little... there's a gasket in there that you are trying not to damage.


Like so. It was hard to get the picture, and do it at the same time, but a lot will come out when the case starts to open. Obviously, you will have your drain pan under there... and eventually, the case will be empty.

Then, retighten the 7 bolts you loosened, and wipe the excess off the diff, from the area where it was slobbering out of the case...


Having done that, you now will set up your pump again, fill this case with 75w90 Mobil 1, and when full, replace the fill plug.

This is a big case. Took me almost 6 quarts to fill it.

And you're done!

You are now feeling the smugness and self-satisfaction of someone who has done it themselves and saved a ton of cash.

PS Note: there are a lot of similarities between this truck and a Tahoe, Yukon, Envoy, Trialblazer. A lot of big similarities. However, keep in mind, a lot of those other trucks DO REQUIRE AutoTrakII fluid, the blue stuff. THIS truck didn't need the blue stuff, but MANY DO!!


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  • 4 years later...

Good info...

So, save yourself some big cash, and just refill it with Dexron III (or Dexron VI) at a far lower price.

One thing I would add about using Dexron VI in manual transmissions or transfer case that did not call specifically for Dexron VI. Read This

This information applies to 2007 and prior GM passenger cars and trucks.

Dexron III is being phased out as a product name. It is being renamed Manual Transmission Fluid and carries p/n 88861800 U.S. (88861801 Canada).

If fluid p/n 88861800 U.S. (88861801 Canada) is not yet available when servicing a manual transmission or transfer case, Dexron III can be used in its place.

The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.


Unavailability of manual transmission fluid part number 88861800 U.S. (88861801 Canada).


If fluid part number 88861800 U.S. (88861801 Canada) is unavailable when servicing a manual transmission or transfer case, Dexron III can be used in it's place. DO NOT use Dexron VI in place of the manual transmission fluid in any manual transmissions or transfer cases as a failure may result.

Please follow this diagnostic or repair process thoroughly and complete each step. If the condition exhibited is resolved without completing every step, the remaining steps do not need to be performed.

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Dex3 is being renamed manual trans fluid? So my car which uses dex3 and has an automatic trans now uses manual trans fluid? Yes I know the copyrighted dex3 name is gone but there is all kinds of "dex3 compatabile" fluid for sale now.

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