[x-type] Easy Transfer Case Fluid Change

Well, I have finally completed my easy transfer case (TC)
fluid change and am pleased to say that it works.

First, let me give credit to Anthony Hladun and all those
others who have done this in various manners before. I want
to acknowledge that I used all your good work as a
foundation for my method.

What I wanted to do was to come up with a method and
associated hardware that would be easy enough to do so that
I could change it as often as I wanted to and I needed to be
able to do it on an automatic transmission car where the
space is very tight. I also wanted to avoid cobbling
together bits and pieces if possible.

The solution I came up with was a one-way valve to replace
the drain plug and a pump that would meter the fluid you
pumped in.

The valve I had made is shown in the pictures below. The
valve body is high carbon steel with male pipe threads to
allow it to screw into the transfer case in place of the
drain plug. The valve body and gate or plunger are carbon
steel, the spring is stainless steel, and the seal is Dupont
Viton rated for use with petroleum products. The cracking
pressure on the valve is only .125 PSI and the length of the
valve is 1.3’’. I chose this length so that the open end of
the valve is slightly recessed into the pocket of the TC
when the valve is snugged into place. (See picture #6 below)

In addition, I fashioned a 90 degree elbow with a short male
nipple so that I could thread it into the valve in the small
space available in automatic transmission cars and purchased
a 2’’ nipple and reducer that screw into the elbow, a
magnetic drain plug to fit the female (open) end of the
valve, a roll of petroleum specific Teflon sealing tape, and
a CRC hand pump that delivers 1 fl. oz. per stroke.

Here’s what I did (see pictures below).

  1. Remove the drain plug (My TC was dry!!!)
  2. Install the valve with Teflon tape sealant specific to
    petroleum applications
  3. Install the elbow loosely (two turns was sufficient)
  4. Install the reducer and nipple loosely
  5. Slide the flexible plastic hose from the pump over the
  6. Pump 400 ml (13 strokes) of approved gear lube into the TC
  7. Remove the pump, nipple, and elbow leaving the gate
    valve to hold the fluid in the TC
  8. Install the magnetic plug into the female end of the
    valve to protect it from the elements and to serve as a
    back-up seal.

I pumped in 400 ml because that is the amount you can drain
from a correctly filled TC using the drain plug. I am
attempting to source the valve with a magnetic gate but do
know if that will be possible. The valve I had made cost me
over $50.00 as is but buying in small quantities may lower
the price. All in I have ~$100.00 into the system using
one-off sourcing without the gear lube. I am exploring
sourcing small quantities and offering all the parts with
detailed instructions as kits. The installed product looks
quite professional IMHO.

Wild Bill
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1 Like

In reply to a message from Wild Bill sent Sun 16 Nov 2008:

Good idea. Always like to see creative solutions to
these ‘‘overlooked’’ engineering designs. Anthony’s original design
solved lots of problems for lots of people and I’ve recommended it
to many.

I haven’t had occassion to have a TC out of the car in a long time
now, but I’ve meant to try another method if I ever do. I’d replace
the top fill plug with a threaded 3/8’’ barbed fitting, then
permanently affix a 3/8’’ fuel line fed up to the top of the engine
bay. That way I could feed the fluid in from the top with a clean
drain and replacement of the original drain plug. The fuel line can
then be capped or just left open as it would work like another case

Good luck with your project.

BTW, for anyone doing this, you should use the proper new gen
replacement fluid. In the US, one source that specifies the correct
compliance is Sta-Lube Syn-Go. Find it at NAPA stores. I’ve use it
many times as replacement fluid. I personally don’t like the idea
of ‘‘experimenting’’ with different fluid formulas, especially older
formulas that have been around for a long time and predate these
fill-for-life designs.–
Steve Hannes - 02 XK8 - 96 VDP - 02 X-Type - BMW Z3
Phoenix, AZ, United States
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In reply to a message from Wild Bill sent Sun 16 Nov 2008:

Your system looks staightforward and easy to install. I would
defnitely be interested in purchasing a setup if you went into
small scale production. Changing the fluid at the dealer is a
multiple hour charge.
Steve Bruce–
Steven Bruce
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In reply to a message from Wild Bill sent Sun 16 Nov 2008:

Message from Australia re Transfer Box Failure
We have found one of the contributing factors to the X-type AWD
transfer cases having little fluid in them (and eventually failing)
is a oil leak from the GKN viscous coupling (which comes off the
back of the transfer box and connects to the propeller shaft). The
leak shows as gluggy oil/grease coming out of the front CV joint of
the prop shaft and depositing itself on the ground when you park.
This happens because the leaking oil from the transfer box runs
down the spline of the output shaft during driving and dilutes the
graphite grease in the front propeller shaft CV joint - which then
ozes out. Fortunately, the viscous coupling oil seal can be
replaced in situ by a competent mechanic, avoiding a costly
transfer case removal (and/or replacement). The remaining tranfer
oil is then replaced and refilled using a method such as described
above by Wild Bill. Preventative maintenance can then save what
would otherwise eventually become a very big bill!–
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In reply to a message from BGJ sent Fri 12 Dec 2008:


I am trying to follow your logic, but I’m not sure I understand
what you’re saying. The GKN Viscous Coupler is located on the
mainshaft of the transfer case and does not feed the rear prop
shaft. Do you mean VC (Viscous Coupler) or do you mean the CV
joint, which is located outside the transfer case on the right
front axle half shaft? It makes more sense, as there are many
reports of the right side case seal failing allowing precious TC
fluid to possibly flood the RS CV and dilute the CV grease.

The GKN VC is a sealed unit (welded shut) in assembly. It is hard
to believe this unit leaks and I’ve known of no cases at all where
this has happened. There are some pictures of the VC shown in its
stackup assembly in the transfer case and lone shots of it too on
this site:


You’ll have to cut/paste the entire string in your browser.

I believe the low oil levels come from the extremely harsh
operating environments under which the transfer case operates. To
begin, the TC only contains 600ccs of fluid (about a pint). That is
only about 1/3 to 1/4 the oil quantity found in a typical
differential. Then the transfer case is placed right up against the
engine block and direcly under the right exhaust manifold and
catalytic converter. Because of the extreme heat, Jaguar
engineering added an 11th hour jerry rigged fix, the notorious
plastic air scoop that gets ripped off between each oil change.

I believe the transfer case gets so hot under normal operating
conditions, that the TC fluid is literally boiled away over time,
witnessed by the lack of any leaks on driveways as would be
reported by owners.

I am interested in any more specific info you have if you don’t
mind sharing.

Steve Hannes - 02 XK8 - 96 VDP - 02 X-Type - BMW Z3
Phoenix, AZ, United States
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In reply to a message from Wild Bill sent Sun 16 Nov 2008:

Thanks to all of you guys for the input on the transfer
case oil change. I changed the fluid yesterday. What an
ordeal! AND, I am a mechanic. It’s not that difficult,
however the situation is not good.

Here is what I did:

I removed the drain plug to find a DRY transfer case. It
may be leaking through the aft prop shaft CV, dunno yet.

I then positioned my small parts cleaner under the TC and
flushed out the transfer case with a kerosene and oil mix.
This is a successful way to remove grit. While still up in
the air, I ran the car in 5th gear at idle while flushing
the TC. Then drained and sucked as much out as possible.

I then filled it with 1 quart of proper lube (thanks Steve)
and ran it in 5th again. I then drained this out, and
filled with 500cc proper lube via a hose barb and hose.

I then removed the hose, capped the barb and got ready to
install the OEM magnetic drain plug in it’s proper
position. I lost about 100cc of lube when putting the drain
plug in. So, that should be quite close to the proper
level. If not, it’s way better than NONE!

The original message included these comments:

Well, I have finally completed my easy transfer case (TC)

2003 X-Type 2.5L 5 speed
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In reply to a message from BGJ sent Fri 12 Dec 2008:

Hi Steve
Thanks for the questions. Got me thinking.
Looks like I got some of the parts confused! Ignore reference to
the GKN Viscous coupling, I was actually refering to the output
shaft of the transfer box where it connects to the flange that
bolts to the front CV joint of the rear prop shaft. Oil can travel
down the splies of the output shaft, gets into the grease of the CV
joint and you end up with blobs of grease on the ground under the
car. If this happens it is necessary to replace the seal and make
sure you seal off the splines where it goes into the flange with
loctite - my mecanic used locktite 620. Obviously, you then refil
the transfer box as described. Have you had experience of the
problem I am (trying) to describe?
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In reply to a message from BGJ sent Sun 14 Dec 2008:

Hi Brian,

Yes, makes much more sense.

Both outward facing shaft seals, one at the right front axle half
shaft and one at the rear prop shaft fail at a pretty regular rate.
These are both field replaceable. The only other shaft seal, a
special double sided seal is internal and separates transaxle
fluids from transfer case fluids. It is not field replaceable and
cannot be purchased to my knowledge. I can’t say I know of any
failures with it unless self-induced by not following factory case
removal instructions.

If the GKN viscous couple were to lose its special sealed fluid, it
would just quickly mix TC fluid. I’ve not heard of using Locktite
on the splines…Interesting, Thanks!–
Steve Hannes - 02 XK8 - 96 VDP - 02 X-Type - BMW Z3
Phoenix, AZ, United States
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In reply to a message from skhannes sent Mon 15 Dec 2008:

I agree 100% with the three views that the TC is really
dependent on a very small amount of lubricant, the TC runs
very hot due to proximity to the engine, cat, etc., and that
not changing the fluid is a recipe for burning out TC’s.

Having played around a bit with changing the TC lube, I have
decided that there is probably more at work here.

The TC is not really a sealed unit. There is a breather on
the top beside the un-accessible fill plug. Now the reason
for the breather is pretty obvious. The TC gets hot and the
air (and probably also the lube) expands and the breather
lets out the pressure build-up so you don’t blow out the
seals. That seems pretty reasonable and necessary to me.
But there are two other things that happen with this system.
First, some of the hot lubricant will escape into the
atmosphere lowering the amount of lube in the TC. That’s
why we have had PCV valves rather than breathers on engines
lo these past 40 years. Heat up the lube in a nice toasty
TC, whip it around with the gears and shafts so you get a
nice mist inside the TC, and over 10 or 20 or 30 thousand
miles, you have lost a pretty significant amount of what
started as in minimal amount of lube in the first place
through the breather.

But there’s yet another thing taking place. Eventually, the
TC cools or you run through a puddle and splash water on it
for an instant temperature drop and the opposite of heating
it happens. You draw in cool moist outside air and get
instant condensation inside the case. Gas tanks are sealed
in part to prevent this and they don’t even get hot.

Since I now change my TC coolant regularly since it is so
quick and simple, I’ve noticed that in a fairly short period
of time, say 5,000 miles, the TC lube is a dark brown and
looks (I’ve not had an analysis done) like it has been
contaminated with water. I know that look from working on
construction equipment in another life long ago.

In short, I believe that it is just prudent to change the TC
fluid each oil change (every 5K miles) or at least every
other oil change.

I never cease to be amazed at how bad the lube looks after
5K miles. If it were engine oil, you’d be looking for a
machine shop or a used engine. It really looks that bad.

Just my $.02 worth.–
Wild Bill
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How much for you to make me one of those valves?