Unfortunately the service
procedure page for Classic Transmissions was overwritten at some point in
the distant past and has not been located in the existing back up files.
If you would like to submit a
proper write up for the Classic model transmission service it would be
greatly appreciated.
Picture at Right: Transmission oil pan on John's 4.0 looking
rearwards. See detailed description of duplicate image below left.
Introduction
Transmission service time comes around every 30,000 miles
according to the official service schedule. At this time the
transmission oil needs to be drained and refilled, and (less easily
accomplished) the transmission oil filter needs to be replaced.
Accessing the filter requires removal of the transmission oil pan. On
the Classic this requires removal of the adjacent chassis cross member,
requiring special tools and techniques, in addition to unbolting the
exhaust downpipes at the manifold. Fortunately the designers of the P38 managed to come up with a more sensible arrangement of
underbody components, but the trans filter operation is still a bit of
a challenge compared to most other routine maintenance operations. This
page endeavors to ease the pain of the operation.
Draining the Fluid and Removing the Pan
The first order of business it draining the transmission oil
from the drain plug at the bottom of the pan. A 17mm wrench is needed
to remove the oil drain plug. Note the magnetic center of the plug
which collects steel particles from the oil -- you should clean this
before replacement.
After removing the plug and draining out the oil, you can replace the
plug and remove the black transmission oil cooler return line (at top
left in left hand image below) from the oil pan. A large Crescent
wrench (bigger than 10 inch) will do the job. Be prepared for more oil
to drip from this pipe after it is removed.
Transmission
oil pan
on author's 4.0 looking rearwards. Black return pipe from
transmission oil
cooler enters oil pan at top center left. Forward drive shaft (prop
shaft) at right.
Note tubular chassis crossmember at bottom of picture
(mine is dented at lower left from hitting off-road obstacles).
Similar view after removing
transmission oil pan. Rags at top of image are to protect disconnected
end of transmission oil cooler return line and stop it dripping. At
center of image is the transmission oil filter with its oil intake pipe
protruding down. Note screw at center holding this pipe in place --
this needs to be removed. Crossmember is below bottom of picture.
Next, the pan has to be removed. It is held in place
by six 10mm bolts arranged around its edge (two of which are visible at
top of picture above left). Most of them can
easily be reached with a 10mm socket with medium extension, but
the left rear bolt is in
an awkward position and is much easier to access if you remove the
chassis crossmember (see
optional
chassis crossmember removal section below). However with a universal joint on the socket
extension, or even a
compact 10mm ring spanner (box wrench), this step can usually be
avoided.
One other problem remains if the crossmember is not removed -- a large
15mm bolt at the center of it (see pictures below kindly supplied by Ron Beckett) prevents
sufficient clearance to remove the pan once it is
unbolted. Accordingly, it is best to remove this bolt as a preliminary
to removing the six pan mounting bolts. Interestingly,
as evident in the picture above left, this bolt is not present on my
1995 4.0SE, so there is no problem at all. (Readers please help here
and tell us if the bolt is only there on the 4.6 due to the slightly
different transmission used, or only on later models than mine).
With clearance secured and the six mounting bolts removed, the pan can
be moved forward and
downwards to clear the chassis crossmember. The pan will still have
some oil in the bottom of it, as the drain plug is cleverly designed
not to be at the lowest point. Once the pan is off, oil will start
dripping from all the exposed transmission parts, so keep your drain
tray or container underneath.
Removing the Filter
At this point the shop manual says to remove the bolt holding
the trans oil intake pipe (picture above right) and two bolts holding
the filter in place (picture below left). It neglects to mention that
these are actually long machine screws with Torx T-27 heads. They can
be fairly tight but using a good Torx wrench on them will usually do
the trick. Remove the single intake pipe bolt first. Then the spacer
under the bolt head, and the bracket with the intake pipe can be pulled
off.
Another view (taken from left
side of vehicle) of the filter in place, showing the two filter
attachment bolts at upper left (Torx T27) and the trans oil intake pipe
at right.
Oil line to transmission cooler is at left.
Rearward view of transmission
underside after removing filter. At top right is filter outlet
connection (see filter top photo below right)
Next the two other bolts
holding the filter in place can be removed, and the filter will drop
off. More oil spillage is bound
to occur as you remove these three torx screws, as some oil will be
left inside the filter and will spill out as it tilts down, so leave
your oil collection pan in place under the vehicle.
Installing the New Filter
New filter: Bottom view with
intake at top right; new O-ring in place. Hole at lower right is for
mounting bolt & spacer for curved inlet pipe (see
above).
Top view of new filter. This
side goes against the transmission underside. Outlet is shown at top
right with new O-ring in place.
The new filter can now be prepared for installation by fitting the new
O-rings that hopefully came with it to the inlet and outlet openings
(see pictures above left and right). Lubricate the O-rings with new
transmission oil.
The new filter is the offered up to the bottom of the transmission and
bolted into place with the three torx bolts. First you can loosely
install the two bolts near the filter outlet (two holes at top
right of image above right) and then you can loosely reinstall the
curved intake tube, bracket and spacer. When everything is in place you
can tighten up all three torx bolts.
Replacing the Pan and Refilling with Transmission
Oil
The old rubber gasket should be removed from the perimeter of the pan
and a new one (which hopefully came with your transmission filter kit)
installed. Then the pan can be offered up to the underside of the
transmission and bolted into place with the six 10mm bolts. Needless to
say, during this process you should take steps not to get dirt from
the vehicle underside into the pan -- this is easier said than done on
a Range Rover like mine that has seen more dirt than pavement!
Making sure you replaced the drain plug, you can now refill the
transmission with oil. It might not be obvious that the filler hole is
simply the tube used for the transmission oil level dipstick! Just
remove the dipstick, insert a funnel, and pour the oil in (ATF/Dexron
III).
Here I ran into a snag as the driver's handbook
and shop manual specify 9.7 litres capacity (about 10 US quarts) for
all engines and years except 11 litres for the 94-98 4.6. For a refill
this is a total work of fiction. The amount of old oil I drained out
was only about 5 quarts. (Presumably the remainder stays in the torque
converter and the transmission oil cooler circuit). There are dire
warnings not to overfill the transmission, and there is only 0.25 quart
between the upper and lower markers on the dipstick. So, you have to be
pretty accurate in your guessing of how much to put in. The oil level
has to be measured at idle with a cold engine, after shifting the
tranny
through the gamut of positions and back to Park.
I found about 5 and a half US quarts was the right amount for refilling
the transmission on my 4.0 to the top of the markers on the dipstick;
slightly more should be needed on a 4.6.
Optional Removal of Chassis
Cross Member
Paul Bryant
reports on doing the procedure on his 98 RR. To improve access he opted
to remove the chassis crossmember, using a bottle jack
purchased
from a wrecker to spread the chassis rails. (He elected to use a
mechanical
jack as most hydraulic Jacks won't work if they are lying on their
side).
He was so successful, he came close to a head injury when the
cross-member
fell out from between the chassis rail! For more details on this
routine procedure, see the Transmission
Service section of the Classic RR Remedies Page.
Callan Campbell
prefers to remove only the single 15mm bolt as described earlier, and
reports "The only reason I tend
to lower the crossmember or remove it is if I'm removing the
transmission to replace the rear engine seals or to work on the cat.
converter."
Parts Needed
The transmission filter, the two O-rings for the filter intake and outlet, and
the pan gasket are usually sold as a kit, which also includes a new brass washer
for the transmission oil drain plug.
