AW 55-50SN / AF 23-33 Diagnosis and Valve Body Information

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AW 55-50SN / AF 23-33
Diagnosis and Valve Body Information
Presented by
Bob Warnke
ATRA Powertrain Expo 2008
800-843-2600 • 802-463-9722 • F: 802-463-4059 • • [email protected]

Adapting to the Aisin Warner 55 50SN valve body

Some things are less intimidating, if your not the first one to do it. That statement is relative to both the
crossing of a frozen lake and a problematic 55 50SN. Because of a heavy snow cover, it cannot be as-
sumed the ice is sufficient for support. What you cannot see may result in a sink or swim experience. On
the 55 50SN valve body, a clean core is not indicative of the function.
This material is a route past the “thin ice” that other travelers have marked. At these flag’s per say, the
test or inspection, frequently points to the valve body, as it accounts for the majority of the transmis-
sion’s issues. The 55 50/51 SN is installed into a multitude of vehicles and there will be variations to the
unit and this data. A similar valve body will bolt to a GM, Volvo, Saturn, Nissan, Saab, Opel or Renault.
Failure to test and recognize can create hours of additional effort.

Pressure and fill:
All the pressure plugs have a 12mm head. Do not mistake the 27mm band anchor (see Figures 1 and
2)for a fill plug or pressure tap. If that anchor is removed, the band will have to be recaptured. Position-
ing the band requires removal of the servo, at best and possibly the complete transmission.
The turbine sensor hole can be use to improve the fill speed. Low fluid or excessive overfill, can create
erratic pressure and poor linear solenoid control, eventually forcing a TCM high pressure strategy.
Main shaft Lube
©2008 Sonnax Industries, Inc.

speed sensor
B-4 servo
B-4 tap
27mm band anchor
Input speed sensor
If the transmission is in the vehicle, “test the ice” per say, at the pressure taps relative to these com-
• TCC RPM fluctuation and overheated fluid
Check lube pressure. The lube pressure tap is between the secondary regulator valve and the main
shaft bushings. Lube pressure will be affected by the fluid viscosity (flow rate) and the bushing to shaft
clearance. Sufficient pressure at operating temperature indicates the filter, pump and both primary and
secondary regulators are functioning. Normal lube pressure at the port indicated; -10 f. lube pressure
can be as high as 30 psi. At 150 f, normal lube will be 5 psi. in Drive and 8 psi. in Reverse. This indi-
cates the bushings are in place and can retain some of the source pressure. Lube pressure that starts
low and stays at zero psi, would indicate your pump output is low, the regulator valve bore is worn or
your bushings are bad.
If you are diagnosing a TCC complaint perform a cooler flow test. Normal flow in Drive with TCC re-
leased is 1.3 gpm and during TCC apply it drops to .7 gpm. The Saab, cooler element will require an
adapter, but most units are easily accessible.
Lube pressure and flow on the 55 50SN, is low in comparison to other units. This converter requires
multiple valves, along with the rear pump bushing, to control modulated TCC apply (see Figure 3). The
converter clutch may remain fully applied at very low speed and high load, which taxes the fluid and lin-
ing, creating a break-away slip or RPM fluctuation.
©2008 Sonnax Industries, Inc.

• Delayed engagement and poor/flare shifts
Check SLT pressure and C-1 clutch. The C-1 clutch is engaged via pressure rise by SLT solenoid
and through a series of modulated valves. The SLT pressure should start at 5 psi. in Drive and increase
with throttle and load to 80 psi maximum. SLT will cutback and spike on various shifts, depending on the
TCM program.
Typical C-1 pressure is -0- in Park. As Drive is selected, it quickly steps to 25 psi., then 50 psi, within
half second and remains, until accelerated. C-1 psi. will then follow load, with a maximum near 200 psi.
If C-1 pressure upon selecting Drive is immediately 160 psi. and obtains 200 psi. during a shift, the unit
may be under a TCM code/ failsafe mode. Engagements at this time are abrupt. Some vehicles ( Volvo
specifically) may use a C-1 disengagement via brake signal creating a neutral at idle. Check for a TCM
flash to eliminate this condition.

2-3 shift flare, neutral or harsh
Compare the B-4, servo apply pressure, to the C-1 clutch. The B-4 tap is at the top of the case, in line
with the linkage bolts.
The B-4 circuit has extensive valve body control and includes a tube with o-ring ends that feed the
servo. Comparing C-1 to B-4 is an indication of control by the SLS and SLT linear solenoids, a failsafe
or leakage condition.
Proper B-4 pressure should follow C-1 and never be less than 10 psi.of C-1. (Refer to the C-1 pres-
sure testing.) If C-1 psi. is fixed at 160 psi. upon engagement, the 1-2 and 3-4 shift, may be acceptable,
but the 2-3 is generally too harsh. A TCM pressure management, code, aerated fluid or bad speed sen-
sor, will eliminate the SLT pressure curve and force B-4 to an immediate 200 psi. which results in the
harsh 2-3 shift. If the pressure curve of both C-1 and B-4 are parallel, C-1 initial engagement is near 50
psi. and the 2-3 harsh, the vehicle may require a flash update, but perform a key cycle and numerous
drive cycles first. Some manufactures ( Volvo) have servo’s and a reflash to improve 2-3, 3-2 drive-
Lock up

gear lube
SLT accumu-
lator bore
Critical pump stator bushing
©2008 Sonnax Industries, Inc.

SLT air test:
Before removal of a valve body, from the transmission, you can perform a visual wet air test of the
SLT circuit.
If you pressurize the SLT port with shop air ( 80-100 psi), air pressure will push fluid, which you see as
a leak. Problematic leaks occur at the steel side cover, SLT accumulator, B-1 and C-1 control valves. A
major leak or combinations, cause delayed engagement or flare up-shift and should be inspected after
You can perform a similar air test (ill#4) with the valve body itself. When doing so, the pump line port
and thermal element hole must be closed and the separator plate held as shown to eliminate cross
leaks. This might sound confusing in print, but when you do it, the ports will be evident and easy to
close with an opposite hand.

Cast #
Plate code
Vented/no vent
Up or Down

No code=earliest
Insulator color
©2008 Sonnax Industries, Inc.

Valve body inspection:
There are many variations, which complicate coring and matching parts. Figure 5 identifies visual
changes. Currently there are 6 different shift solenoids, 4 of which can be installed in incorrect loca-
tions or replaced by a normally open vs. normally closed solenoid. The shift solenoids should be
checked for proper flow when open and their seal when closed. These are fed line pressure from an ori-
fice in the plate and can be over pressurized.

Three linear solenoids are calibrated to the valve body. Exchanging SLT, SLS solenoids between
cores, without adjusting to the valves, is generally not acceptable. Don’t hesitate to open and inspect
the valve body…as it’s comparable to other Asian Warner designs and not difficult to reassemble. That
inspection should include all the removable sleeves, both regulator valves and the solenoid modulator
bore. The linear solenoids are fed by this modulator valve which limits the maximum pressure. When
that bore is worn, the concern is similar to a bad GM actuator feed circuit.
Excess wear appears as a discoloration, or polished area, in the shape of a moon phase, generally at
the ends of the bore or opposite side of fluid entry (see Figure 6).

Note the shadow from
Excess bore wear
©2008 Sonnax Industries, Inc.

55 50 SN &/or AF-23/33
SLU Black Green
5.0-5.6 ohms
TCC apply, reverse
at 68°
1-2, 2-3 up/down shift
SLT Blue Green

5.0-5.6 ohms
Line rise, engagements,
at 68°
converter pressure
SLS Green Blue
5.0-5.6 ohms
Clutch pressure, shift
at 68°
S1 Black White N.O.
13.5-15.5 ohms
1st, 1-2 shift, reverse
at 68°
S2 Black Black N.O.-G.M.
13.5-15.5 ohms
2nd, 3rd-4-5 shift
at 68°
S3 Gray Yellow N.C.
13.5-15.5 ohms
Reverse, fwd-engage, 3-
at 68°
4 shift
S4 Blue
13.5-15.5 ohms
3,4,5, 2-3 shift
at 68°
S5 Green
13.5-15.5 ohms
Reverse engagement
Black - ‘02

at 68°
Wiring Issues (see photo left)
Common to mix up connectors
from harness
S1- White wire, right side loom.
S3- Yellow wire, left side loom.
S-1 wire, white
S-3 wire, yellow
©2008 Sonnax Industries, Inc.

Shift Solenoids

S-1 S-2 S-3 S-4 S-5
P off off off off off
R off off on off on

N off off off off off
D-1 on on on off off
D-2 off off on off off
D-3 off on on on off
D-4 off on off on off
D-5 off off off on off

Solenoids S-1 and S-2 are on same TCM driver.

Solenoids S-4 and S-5 are on same TCM driver.

Solenoid S-3 is independent/separate.

©2008 Sonnax Industries, Inc.

SL Solenoids
Note: This OE chart is
referring to line pressure.
Actual SL output is lim-

ited by solenoid modula-
tor valve to 80 psi.

End of solenoid manifold to shoulder on adjuster
Preliminary adjustments:
.010”-.050”, record prior to re-

Measurement taken with retainer
removed. Shoulder of adjuster to
end of manifold.
Turning screw inward, raises SLT
& SLS pressure
6 clicks = 1/2 turn.

Turning screw inward, reduces
6 clicks = 1/2 turn.

Adjustment clicks are created
by the increments on exterior
of threaded allen, 3mm

Control valve
With control valve removed,
shaking the coil should result
in a free pintle movement.

©2008 Sonnax Industries, Inc.

All solenoids are 5.0-5.6 ohms and operate at 300Hz. Between 10 and 40% duty cycle.

Note: Bracket changes on Linear solenoids. Length of Linear SLT-SLS varies.
Early short brackets
Long late bracket
©2008 Sonnax Industries, Inc.