Installation Instructions
Shift Improver Kit
for
1988 and Later TurboHydramatic 400
TH-400/TH-475 (3L80/3L80-HD)
Part No. 20261
©B&M Racing & Performance Products 1992
IMPORTANT MANUFACTURING
DATE CHECK: Hydramatic introduced
a revised transmission case just after
the beginning of the 1988 model year.
If you are installing the B&M TH-400
Shift Improver Kit in a 1988 vehicle
you must check the Julian date stamped
on the transmissions I.D. tag (See
Fig. 1) before attempting to install this
kit. Do not use this kit (#20261) in
transmissions built before November
23, 1987 (Julian date 327), use instead
our #20260 Shift Improver Kit which
is designed to be used with the earlier
style case. If the I.D. tag is unreadable
or missing you will have to remove the
oil pan and valve body from the transmission to determine if your transmission has an early or late style case
(See Fig. 2). The manufacturing date
check applies only to 1988 transmissions, this kit (#20261) will work correctly in all subsequent application
years specified in the heading of these
instructions.
We recommend that you read
through the instructions completely
before beginning the installation
so you can familiarize yourself with
the installation procedure and tools
required.
Check the tool list at the rear of
the instructions to make sure no
parts are missing and you have the
tools required to install your B&M
TH-400 Shift Improver Kit.
Installation of the B&M TH-400 Shift
Improver Kit can be accomplished by
anyone with minimum mechanical experience. It is however, important to
closely follow the instructions. Read
each step carefully before proceeding,
if you do not understand, go back and
read the step again. Installation of the
kit can be accomplished in several
hours.
NOTICE: The B&M TH-400 Shift Improver Kit is not a cure-all for an ailing
transmission. If your transmission is
slipping, chatters or is in poor general
shape, the installation of this Transpak
may worsen the condition. However on
a properly operating transmission in
average condition, the B&M TH-400
Shift Improver Kit will provide the kind
of transmission performance you are
looking for.
When installing your B&M TH-400
Shift Improver Kit there are several
other B&M performance products you
may wish to consider:
TRANSMISSION OIL COOLER We
feel that it is very important that every
vehicle used in heavy duty and hi performance applications (racing, towing,
RV, etc.) should have an oil cooler.
Heat is the major cause of transmission failures, and an oil cooler is an
inexpensive safeguard against overheating and transmission failure. B&M
offers a wide variety of transmission
coolers to suit every application.
TRICK SHIFT PERFORMANCE ATF
#80259 Trick Shift performance auto-
matic transmission fluid is the industry’s only real performance ATF. A
specially blended oil with foam inhibitors, extreme pressure agents and
shift improvers, this fluid assures protection while delivering the fastest possible shifts. You literally “Pour in performance.”
DRAIN PLUG KIT #80250 The TH-400
transmission is not factory equipped
with a drain plug. The B&M Drain plug
kit is inexpensive and easy to install. It
eliminates the mess of pan removal
and gasket replacement normally required when changing fluid.
DEEP PAN #20289 B&M offers deep
pans for the TH-400 transmission that
provide 3 to 4 quarts additional oil
capacity which significantly contributes to the cooling ability of the oil. No
modifications to the dip stick are necessary and a fluid pickup extension is
provided.
TORQUE CONVERTERS B&M offers
a wide range of street torque convert-
Printed in U.S.A.
9500455-02
Transmission I.D.
Nameplate Location
JULIAN DATE
QU 000 A
88 QUA 0000
Model Year
88=1988
89=1989
90=1990
Figure 1
ers for the TH-400 transmission. See
your B&M dealer for details of the
correct torque converter for your vehicle.
ADJUSTABLE VACUUM MODULATOR #20234 This replacement vacuum
modulator for the TH-400 has the added
feature of being adjustable. The adjustable feature allows you to tailor your
shift points within a range of 2-4 mph.
Remove bolt to remove filter
Serial Number
A= TH-400/475
(3L80/3L80-HD)
The 1987 and earlier TH-400 has no checkball in this location and
must use Shift Improver Kit #20260. If you have a checkball in this
location, this kit (#20261) is the correct one.
Figure 2
FILTER SERVICE KIT #20287 The
filter service kit replaces the stock
factory filter with aspecial filter that
uses a a much finer felt micronic element which also has more total filter
area so that the finer filtering element
does not cut down on oil flow. This kit
includes a special heavy duty oil pickup
tube that is seated to the case with a
double O-ring seal and is spring loaded
to eliminate air leakage.
TEMPERATURE GAUGE KIT #80212
Most transmission and converter failures can be traced directly to excessive heat. The B&M transmission temperature gage can save you a costly
repair bill by warning you ahead of time
of an overheated transmission. The
B&M temperature gage is extremely
accurate and dependable, it comes
with all necessary hardware and is
easy to install.
B&M SHIFTERS; B&M manufactures
a complete line of automatic transmission shifters ideally suited for use with
the TH-400. These shifters provide you
with positive transmission control as
well as stylish appearance for your
vehicles interior.
TH-400 KICKDOWN SWITCH #20297
When installing a TH-400 transmission
in a custom installation in place of a
TH-350 or a TH-700 this kit provides a
kickdown switch that will fit into the TH350 or TH-700 throttle cable bracket.
Figure 3
INTRODUCTION
Transmission components are precision fit, work slowly and do not force
any parts. Burrs and dirt are the num-
Filter
2
ber one enemies of an automatic transmission. Cleanliness is very important,
so a clean work surface is necessary.
We suggest a clean work bench from
which oil can be easily cleaned or a
large clean piece of cardboard could
also work.
This kit contains all the parts necessary to obtain two different levels of
performance, depending on the vehicles
intended use:
1. Heavy Duty; Towing, campers, motor
homes and 4-wheel drive vehicles.
Heavy Duty level is a good starting
place for light weight, high powered
vehicles such as street rods. Heavy
duty level produces firm noticeable
shifts.
2. Street; Dual purpose performance
vehicles, street and strip performance
cars and, off road vehicles. Street level
produces very firm, positive shifts.
DISASSEMBLY
Automatic transmissions operate
at temperatures between 1800F and
2400F. We recommend that the vehicle
be allowed to cool for several hours
before attempting disassembly to avoid
serious burns from hot oil and parts.
The vehicle should be raised so there is
at least 2 feet ground clearance for
ease of installation and safety.
MAKE SURE THE VEHICLE IS RIGIDLY AND SECURELY SUPPORTED,
JACK STANDS, WHEEL RAMPS OR
A HOIST WORK BEST, DO NOT USE
JACKS ALONE.
STEP 1. Have an oil drain pan ready
to catch oil and a clean tray on which
to put small parts so they won’t get lost
or dirty. Drain the oil by removing the
rear pan bolts and work towards the
front leaving the two front bolts in place.
If the pan is stuck to the case pry the
pan loose with a screw driver. Slowly
remove the remaining two front bolts
allowing the rest of the fluid to drain.
STEP 2. Oil filter removal (See Fig.
3): Remove the shoulder bolt holding
the filter then pull the filter straight
down. Some models also use a spacer
between the filter and valve body. Watch
out for oil splatter. If the oil pick-up tube
did not come out with the filter, pull it
out. Remove the O-ring from the bore
in the case if it did not come out with
the oil pick-up tube. Be careful not to
scratch the case bore when removing
the O-ring.
STEP 3. Observe the location of the
Governor
tubes
White smog
switch wire
Governor tubes
following (See Fig. 4) Manual linkage,
detent spring with roller and the way
the internal shift lever pin engages the
manual valve in the valve body, governor tubes and their routing, detent solenoid (oval or square can) and its wire
connector, white spark control switch
wire and routing of the wire.
STEP 4. There are (3) 1/4-20 and (8)
5/16-18 bolts holding the valve body.
Remove all but one valve body bolt and
Detent solenoid
Figure 4
When removing valve body be sure not to allow
manual valve to fall out and be damaged
Figure 5
Vacuum modulator
Manual
valve
Manual
linkage
Detent spring
Manual
linkage
pin
disconnect the spark control switch
wire if present. Hold the valve body in
place and remove the last bolt. Lower
the valve body while at the same time
pulling straight down on the governor
tubes (See Fig. 5). Place the valve
body in the oil pan to avoid contamination. NOTE: The front servo may fall out
of the case, if it does see Figure 6 for
reassembly order. Use grease or petroleum jelly to hold the servo compo-
3
Figure 6
nents in place.
STEP 5. Use one (1) pan bolt to hold
the separator plate in place while removing the solenoid. Remove the two
bolts holding the detent solenoid (See
Fig. 7) and allow the solenoid to hang
by its wire. Remove the pan bolt and
carefully lower the separator plate. Be
careful not to loose the seven (7) 1/4"
steel check balls that are on top of the
separator plate. The check balls will be
reused. Carefully remove all gasket
material from valve body and oil pan
surfaces of the case and valve body. All
old gasket material must be removed
before the valve body is reinstalled.
MODIFICATIONS
Detent solenoid
Pan bolt may be used to hold
separator plate in position
during removal and reassembly of detent solenoid
Detent solenoid gasket
(not used with square
can solenoids)
Figure 7
STEP 6. 2-3 Accumulator:
Heavy Duty: No modification required
for this level.
Street: Very carefully clamp the valve
body in a vise and compress the accumulator enough to remove the E-ring
(See Fig. 8). Open the vise slowly and
remove the valve body. Remove the
accumulator spring and reinstall the
piston without the spring. Install the Ering.
STEP 7. Street level only: Drill the
B&M Separator Plate orifice indicated
in Figure 9 using the 5/32" (.156") drill
supplied in kit. After drilling remove
burrs from around hole with a flat file or
sand paper.
STEP 8. Thoroughly clean the valve
body and separator plate in clean solvent to remove any contamination.
Remove any old gasket material stuck
on the valve body channel surface.
REASSEMBLY
STEP 9. Check Ball Placement: In-
stall check balls in the locations shown
in Figure 10 as follows:
Heavy Duty: Seven check balls, one
each, in locations 1-7.
Street: Six check balls, one each, in
locations 1,2,3,5,6,7 (do not install
check ball #4).
Remove E-clip with screwdriver
Street level only
Figure 8
Note: Transmissions used in vehicles
over 10,000 GVW do not have a factory
installed check ball in position #7. If
your vehicle is of this type (over 10,000
GVW) do not install a check ball in
position #7 for Heavy Duty or Street
levels.
STEP 10.Place upper valve body gasket (has “C” punched in it) on to the
B&M separator plate (use grease or
petroleum jelly to hold it in place).
Install the plate and gasket against the
case and use a clean pan bolt to hold
it in position for now (See Fig. 7).
STEP 11.Carefully examine Detent
Solenoid. Make sure the rubber seal is
in good condition and has no nicks or
cuts (See Fig. 11). If the seal is damaged, you will have to replace the
solenoid. If the seal leaks the transmission will be in passing gear all the
time. Install the solenoid with two (2) 1/
4
4-20 bolts. Tighten bolts FINGER
TIGHT for now. Remove the pan bolt
you used to hold the plate and gasket
in place.
STEP 12.Insert the governor tubes into
the valve body (See Fig. 5). Lay the
lower valve body gasket (has “VB”
punched in it) into position on valve
body (use grease or petroleum jelly to
hold it in place). Make sure the manual
valve is in its bore. Install valve body
onto transmission guiding the governor
tubes into their holes at the rear of
case. Push up on valve body and tubes
and engage the manual valve on the
internal shift linkage pin. Install one
bolt to hold valve body in place.
STEP 13.Install all the valve body bolts
finger tight. Make sure the detent
spring is in position and riding on the
internal shift lever (See fig. 4). Make
sure the manual valve is engaged with
the internal shift lever pin. Tighten all
valve body and solenoid bolts to 8-10
lb.ft. (11-13.6 Nm). Route the white
spark control wire and connect to pressure switch on valve body. Check operation of manual valve by running range
selector through all gear positions.
STEP 14.Inspect your filter for damage or clogging. If it has more than
20,000 miles on it we recommend it be
replaced. For longer transmission life
and improved pump operation install
B&M Filter Service Kit No. 20287.
STEP 15.Install two (2) filter O-rings
on filter pick-up tube (See Fig. 12).
Lubricate O-rings with clean ATF then
push pick-up tube and filter assembly
up into transmission, install spacer (if
present) and shoulder bolt then torque
to 8-10 lb.ft. (11-13.6 Nm).
STEP 16.Clean oil pan and scrape off
any old gasket material from pan and
case. You may want to install a B&M
Drain Plug kit before installing the
pan. The drain plug kit will help eliminate the mess when changing transmission oil. Install pan and new gasket
and torque bolts 8-10 lb.ft (11-13.6
Nm).
STEP 17.Add 4 quarts of fresh ATF.
Dexron II is fine for Heavy Duty Level
applications, however we recommend
B&M Trick Shift for Street Level for
firm positive shifts and improved transmission life. With the vehicles wheels
still off the ground, start the engine and
Drill orifice to 5/32"
(.156") hole in this position for street level only.
#5 #6#4
#2
Solenoid: Check to
make sure rubber seal
is in good condition
#1
#7
Figure 9
#3
Figure 10
Figure11
5
shift transmission through all gears.
Place selector in neutral and check the
fluid level. It should be between the
Add and Full marks. Do not overfill !!
This can cause foaming and overheating. Turn off engine and lower vehicle.
STEP 18.Drive vehicle several miles to
warm up the transmission. Park on
level surface and check ATF level. It
should be between Add and Full.
TOOL LIST
1 3/8" drive ratchet or speed
handle
1 1/2" socket, 3/8" drive
1 7/16" socket, 3/8" drive
1 Small flat screwdriver
1 Small Internal Snap Ring
Pliers
1 Small Hammer
1 Torque Wrench 0-10 lb.ft.
(0-13.6 Nm)
1 1/4" Drill Motor
1 Vise
Install two furnished O-rings on
pickup tube. Lubricate throughly
with oil before installation.
Figure 12
TROUBLE SHOOTING GUIDE
Malfunction Probable Cause
Slips Valve body bolts loose.
Low fluid level.
TH-400/TH-475 (3L80/3L80HD) SHIFT IMPROVER KIT
PARTS LIST
Inspect the contents of your Shift
Improver Kit carefully. If you are missing any of the parts shown below, do
not proceed. Contact your B&M
dealer. Don’t forget to purchase about
5 quarts of ATF (See Step 17).
1 20261 Instructions
1 Seperator Plate
1 Oil Pan Gasket
1 5/32" Drill
1 Seperator Plate/Case
Gasket
1 Valve Body/Case Gasket
2 Filter Pick Up Tube O-Ring
Overheating Insufficient cooler capacity
clogged lines or cooler.
Foaming oil at dipstick Fluid level too high.
or breather Clogged lines or cooler.
Erratic shifting Vacuum line cracked or leaking.
Shifter not properly adjusted.
Kickdown switch not properly adjusted.
Low fluid level.
High fluid level.
Valve body bolts loose.
Kickdown solenoid loose.
Late hard shifts Vacuum line cracked or leaking.
Kickdown solenoid loose or damaged.
Kickdown solenoid gasket damaged.
Will not shift Kickdown solenoid loose or damaged.
Governor tubes not properly installed.
Pump buzz or whine Low fluid level.
High fluid level.
Cut, damaged or missing pick-up tube O-rings.
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