Upgrading the 1-2
Accumulator and Changing to Mercon V
If you are seeing sluggish
shifting, shift hunting between lower gears and a very
loud shudder noise during gear changes, you might want
to consider a 1-2 accumulator upgrade. The old piston
has very small o-rings. An OEM piston can rock in the
bore and damage the accumulator walls, if left to long.
The shutter noise sounds like you are driving on those
"you are leaving the road" warning strips that they put
in the asphalt nowadays. The noise can be is very, very
loud. There is a TSB (Technical Service Bulletin) about
this refresh. The new piston and seal has much wider,
tougher o-rings. If the refresh is left undone, your
transmission could be damaged beyond simple repair -
professionals are going to have to fix it for you and
that cost big bucks.
If your Mark or Cougar is not showing the symptoms, it's
still a good idea to at least check to see if your
transmission has the old accumulator parts, change out
the filter and totally drain the old Mercon III and
install the suggested Mercon V fluid. Your next
transmission project will be to add on an aftermarket
transmission cooler. But that is a different article.
For now, here are a few notes on a step by step, if
anybody is interested in doing it himself (or herself if
we have any ladies that like getting down and dirty….)
1. Getting ready to do the repair.
a. The parts you will need are listed below:
i. F7AZ-7F251-AA Updated Accumulator Piston - Retail
Cost $12.00 (Don't use your old one - that is the whole
point of this work you are about to do.)
ii. F4AZ-7F247-A 1-2 Cover and Seal - Retail Cost $3.42.
This part may be optional if you find a new one already
installed. The Cougar had a "new" cover and seal, but an
"old" accumulator piston.
iii. F75Z-7F284-AA Upper (Blue) Spring - Retail Cost
$3.25. This part is optional. You may be able to use
your old spring here. We had one transmission that was
completely missing an upper spring (it was in a Cougar.)
iv. F7AZ-7F284-BA Lower (purple) spring - Retail Cost
$32.50. This part is optional. As you can see, this is a
high cost item. You may be able to use your old spring.
One transmission we did in a 94 Mark VIII had this
spring broken in two places. There is a picture of these
old parts below.
v. Twelve or thirteen quarts of Mercon V or Mercon III -
Retail Cost $30.00 to $40.00. We strongly suggest you
use the Mercon V. It handles the heat better.
vi. Transmission Filter - Retail Cost $5.00 to 10.00. If
you are converting over to Mercon V, replacing the
filter is good practice, since you are trying to drain
the entire transmission of the old stuff. Auto Zone
sells a house brand that comes with a cork gasket.
O'Rielly sells a filter that has a neoprene gasket. I
prefer the O'Rielly filter to the Auto Zone; simply
because of the gasket type makes for easier assembly.
Both filters are USA made and seem to be high quality.
Make sure the gasket is still in the filter box -
sometimes parts houses "borrow" the cover gasket and
forget to return the filter to the "missing parts"
b. The tools you will need are:
i. Seven to nine inch (from tip to handle end) Internal
Snap Ring Pliers. These pliers will compress the ring as
you squeeze the handle. The internal snap ring you will
come up against fits inside of a two-inch diameter bore.
The tips for the pliers should be no larger than 0.09
inches in diameter. Your little 5 inch pliers that you
got from Auto Zone or from O'Rielly isn't gonna have the
muscle to remove the ring. HOTLNC found a high quality
internal/external snap ring tool at NAPA, under their
NAPA Service Tools line. It's a 10-inch tool with many
different sized tips. The good news is that it is
guarantied forever. The bad news is it cost 69 bucks
after taxes. MAPLES 8 showed good, down to earth common
sense and modified a pair of large needle nose pliers.
He ground down the tips to more or less the right size
for the ring hole and applied it to the snap ring. Works
good and lasts a long time.
ii. 10mm and 12mm sockets, ¼ or 3/8 inch ratchet drive,
with extensions and optional screw-driver handle.
iii. Inch-pound and foot pound torque wrenches
iv. 24mm (must check size) socket, ½ inch ratchet drive
or breaker bar.
v. A waste oil container that can hold at least 2
gallons of fluid. The transmission cover will have about
a gallon in it and the torque converter will contain the
vi. A long necked fill tube/funnel (transmission fill
vii. Plenty of show towels or old rags. It's gonna be
raining fluid real soon.
viii. Small scissor jack or hydraulic jack
ix. Jack stands, floor jack or wheel ramps (preferred)
2. Open trunk and turn off the air ride switch.
3. Pull the car up on wheel ramps, or jack it up high
enough so that you can crawl under the car. If you jack
it up, please use jack stands. Do not depend on the jack
to support the weight of the car.
4. Get under the car and start loosing the rear bolts on
the transmission cover. Remove all bolts except for the
two along the front of the cover. As you remove the rear
bolts you will start to see leakage. It will drain
faster if you leave the rear wheels down on the ground
for the drain operation. Once the fluid has more or less
stopped flowing, push the cover back up against the
transmission and remove the remaining two screws. A
third hand would help. A small scissor or hydraulic jack
can also be used to hold the pan up against the
transmission while the bolts are removed. Then carefully
remove the jack and dump the cover full of fluid into
your waste oil container. It's going to rain fluid for a
while after the cover is off, so be prepared for it.
5. The 1-2 accumulator is on the forward, driver's side
of the transmission. There is a round area cast into the
a. To make the snap ring easier to remove, HOTLNC used a
5-inch C clamp to slightly compress the accumulator
seal. He put the moveable end of the clamp on the
accumulator seal. This tool relieves accumulator spring
tension on the snap ring. He then used the pliers on the
ring and removed the ring.
b. Maples 8 used a small jack to press in the piston. We
noted in some applications (A 95 Cougar for example)
using a C-clamp is impossible due to the interference of
the exhaust plumbing.
c. If you do not use the C clamp or jack, you are going
to have to hold the accumulator seal in while removing
the ring. You will be fighting two powerful springs and
they will eventually win.
6. The above picture shows the components that HOTLNC
removed from his daughter's Mark VIII. From the left,
you have the upper (blue) spring. The accumulator
piston. The lower spring (purple color) and then the
seal. Notice that old lower spring is broken into three
pieces. This car had very loud shutter symptoms.
7. The above picture shows the
replacement parts in the same order. The piston and the
seal are made completely different when compared to the
OEM parts. Springs are springs. Depending on your
pocketbook size and the lack of damage to your old
springs, you may not need to buy replacements. Only the
piston and seal need be upgraded.
8. Install the new accumulator parts.
a. Clean out the accumulator chamber and check for
gouges (with that broken spring this worried us. But
only the bottom of the piston and the top of the seal
were beat up - the walls were OK.)
b. Coat the piston's seals with clean fluid and install
the blue (upper) spring into the piston.
c. Push the piston/spring assembly into the chamber,
making sure the piston can compress the spring. This
action may squirt fluid at you.
d. Coat the seal with fluid and install the purple
(lower) spring into the round depression built into the
seal. Push this assembly into the chamber.
e. You might want to use your C clamp (or jack) to hold
the seal into the hole, as these could be new springs
and are much stronger than the old ones.
f. Now install the snap ring. Before removing the C
clamp, make sure the snap ring is completely seated in
the accumulator wall slot.
g. Remove the C clamp and insure the seal rests against
the snap ring all the way around the contact area.
9. If you are going to drain the torque converter, now
is the time to do it.
a. Remove the rubber plug from the inspection hole at
the bottom of the converter cover. It is located just
forward of the transmission body that is still dripping
fluid on you or the floor. Looking inside you should see
the round surface of the torque converter.
b. Using the large socket and ½ inch breaker/ratchet,
mount the socket on the drive pulley bolt and turn the
motor by hand. Turn slowly, as you are moving pistons up
and down. If you feel motor compression fighting you,
stop and let the air bleed off. You are looking for a
12mm bolt head protruding from the center of the
c. Center the bolt head in the inspection opening.
Position the waste oil container under the inspection
hole and remove the bolt. It is quite short and very
d. There may be two gallons of fluid inside the
converter - make sure your waste oil container can
handle that amount.
10. While the converter is draining, remove the old
gasket from the transmission cover and clean the cover.
Look inside the aft end of the cover and find the round
magnet. It is not mechanically attached to the pan, just
stuck there due to magnetism. Remove it and inspect it
for metal filings. The magnet inside the pan may have a
thick coating of black powder-like substance. Don't
worry, it will clean up well. You can clean the outside
of the cover with kerosene, brake cleaner or even
carburetor cleaner if you have that.
11. Replace the magnet and position the new cover gasket
on the cover. Clean off all of the cover bolts. If the
gasket is rubber or neoprene, you can "pin" the new
gasket to the cover using the bolts. The bolt holes in
the gasket are smaller than the bolts, so the bolts are
held in place quite securely. If the new gasket is cork,
the bolt holes in the gasket are too large to hold the
bolts. Position the gasket around the cover. Do not use
"Make-A-Gasket" or silicone sealer. Such sealants are
not needed here.
12. When the converter stops dripping, install the
converter drain bolt into the drain hole and tighten.
Tighten the plug to 21 to 23 foot-pounds. Wipe up any
fluid that has collected inside the converter cover and
replace the rubber plug. Make sure you get the fluid out
of here, or you will be forever worried that your
converter plug is leaking.
13. We suggest you check the torque on all main control
valve body bolts. Set your torque wrench to 80 inch
pounds and check each bolt to insure it is at least this
tight. The specification call for 80 to 100 inch pounds.
There are four or five bolts that are bigger than 10mm.
14. Install the new filter into the transmission.
a. Look inside the filter's install hole and see if the
old filter's grommet is still inside. They can get hard
from the heat and you might find one "heat staked" in
b. Lightly coat the new filter's grommet with axle
c. Install the new filter into the hole and push it
gently up as far as it will go.
d. Align the filter's body edge with the transmission
case and make sure it is sitting more or less parallel
with the valve body.
e. Warning: Once you install the filter, avoid removing
it. Once removed and re-installed, the grommet may not
have enough "spring" left in it to hold the filter in
its position. You may end up having to buy another
15. Double check that the cover gasket surface is clean
and that the mating surface of the transmission is
likewise free of dirt.
a. Install the cover with the pined gasket to the bottom
of the transmission using the cover bolts. Tighten all
bolts a few turns just to keep the pan from falling
b. If you have the cork gasket, install one corner bolt
and match up the cover to the bottom of the
transmission. Start that first bolt a couple of threads
and go to the opposite corner and add another bolt,
being careful to capture the gasket. Keep all the bolts
as loose as you can until to have installed all bolts
into the pan. Having the pan just hanging on the loose
bolts will make it easy for you to determine if the many
bolts are nailing the gasket. Make sure each bolt has
been inserted into the gasket holes. It is very easy to
push the gasket too far inside the case and miss pining
16. Push the cover up against the transmission and hand
tighten the bolts until the cover is fitted to the
bottom of the transmission. Using a wrench, or a socket
driver, lightly snug up all bolts. Using a torque
wrench, tighten all bolts in an X pattern in three
stages. This tightening procedure may seem like
over-kill. But the bolts holding the pan are installed
with very low torque. If you have any bolts too tight or
too loose, that is the location of a future leak.
a. Stage one - torque all bolts to 30 to 40 inch pounds,
using X pattern.
b. Stage two - torque all bolts to 80 to 100
inch-pounds, using X pattern c. Stage three - re-check
the torque on all bolts. You are checking for a value
between 80 to 100 inch-pounds. Divert from the X pattern
here and just go round robin, starting at the center
17. Open the hood and remove the transmission dipstick.
You will find it against the starboard firewall,
slightly lower than the air conditioner hoses. Install
the fill funnel tube into the top of the transmission
fill tube. Did you check the funnel's insides for dirt,
dust and grime? If it ain't finger-licking clean, all
that crap is going into your transmission along with
that expensive Mercon V. Once you have a clean fill
tube, start pouring in the Mercon V.
a. We suggest that you pour in half of what was pulled
out with the motor off. Then jack up the rear wheels,
install jack stands and start the motor. Run through all
the positions on the shift lever, taking the time to
allow the fluid to activate the position selected. One
or both rear wheels may spin.
b. Stop the motor and pour the remaining fluid into the
transmission while it is sitting there. Put in as much
as you took out.
c. Start the motor again and run through the gears
again. Allow to idle for a few minutes and then check
for leaks. Shut it down.
18. Drop the car back on the ground. Clean up, get in
and cycle the shift lever through all the gears. Take
the car for a test drive. Drive it for about 20 miles,
or enough to warm up the fluid. It should be smooth as
glass and no there should be no shutter.
19. Back home, on a level surface, Keep the motor
running and check the fluid level. It should show HOT
FULL. If not add fluid in ½ pint increments until it
does show the proper level.
20. We are done.
1. Author's and Editor's personal experience with their
2. Question and replies on www.markviii.org conference
3. Lincolns Of Distinction, Mark VIII Club, Technical
area, "Parts for Accumulator Piston Repair for 1993 to
1997 Mark VIII's"
4. Ford Mark VIII 1994 Service Manual, (c)1993 Ford
5. Ford Mercury Cougar 1995 Service Manual, (c)1994 Ford
Author: Jerry Heep (HOTLNC)
Technical Editor: Woodie Maples (MAPLES 8)