GM 6T40 (Gen. 1), 6T45 (Gen.

1),
6T50 (Gen. 1) ZIP KIT ®
PART NUMBER 6T40-ZIP QUICK GUIDE
Parts are labeled here in order of installation. See other side of sheet for details on kit contents.

installation Diagram NOTE: All components of this kit

install into the mechatronic unit,
and not the pump. Removal of
the pump is not required for
Main Control this kit, unless vacuum testing is to
Valve Body be performed.

1 NOTE: Continuous spring loading

on retainer clip often raises a ridge
in outboard exhaust ports, making
sleeve installation difficult. If exces-
sive resistance is met during sleeve
1 installation, check for burrs/ridges
at indicated port bore openings and
sand lightly to remove. Ensure all
debris is removed from bore prior to
sleeve installation.
1

1
6
Plastic Checkballs

CAUTION:
Failure to
block
orifice
will result in No
7
Movement of vehicle.

4
WARNING: Spacers should Block AFL Balance
not be used on TEHCMs that Port by drilling and
have plastic fluid conduits. plugging separator
plate where indicated
NOTE: Reference pages 3 and 4 in the using drill bit and
Separator
technical booklet for installation details. aluminum plug
Plate provided (not shown).

In addition to general rebuilding tips and technical information, the technical booklet included in this kit contains vacuum
testing and additional repair options for higher mileage units or for repairing specific complaints which are beyond the
scope of this kit.

©2019 Sonnax Transmission Company, Inc. • A Marmon / Berkshire Hathaway Company 6T40-ZIP_Guide_E 07-12-19
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 GM 6T40 (Gen. 1), 6T45 (Gen.1), Quick Guide
6T50 (Gen. 1) ZIP KIT®

Kit Contents & Installation Steps

Step 1 Replace 5 OE End Plugs Step 5  eplace OE Actuator Feed

R
Place O-ring in groove, lubricate with Sonnax Slippery Stick O-LUBE Limit (AFL) Valve Lineup
and roll on bench to size.
Remove and discard OE valve and spring. Keep outboard retainer clip
Packaging Pocket 1 for reuse. Install Sonnax sleeve and valve as illustrated. Secure sleeve
into bore by installing included clip into sleeve groove at inboard port.
• End Plugs (5) Install included spring and secure all into bore with OE retainer.
• O-Rings (7) 2 extra
CAUTION: Ensure supplied retainer clip is fully seated in AFL
sleeve groove after installation.

Step 2 Replace OE Compensator Packaging Pocket 5

• Sleeve
Feed Regulator Valve
• Valve
Packaging Pocket 2
• Spring
• Valve • Retainer Clip
• Sleeve
• Spring
• Retainer
Step 6 Replace OE Checkballs
Packaging Pocket 6
Step 3 Replace TCC Regulator Checkballs, .250" dia. (6)
Apply Valve Bore Lineup
Remove and discard all OE components except the retainer clip. Keep
retainer clip for reuse.
Step 7  eplace 4 Pressure
R
CAUTION: The small shuttle valve should be positioned with the
rounded end face outboard, and the blind bore inboard. Switch Laminate Discs &
Packaging Pocket 3 D-Rings (& O-Rings when
• Spring
applicable)
• Valve
Reference pages 3 and 4 in the technical booklet for installation details.
• Shuttle Valve
• End Plug Packaging Pocket 7 and 8

• O-Rings (2) 1 extra • Laminated Discs (4)

• D-Rings (4)
• O-Rings (4)
Step 4 Block AFL Balance Port • Spacers (4)
Drill indicated separator plate orifice with included .062" dia. drill bit. WARNING: Spacers should not be used on TEHCMs that
Remove any burrs. Insert .062" dia. aluminum plug into drilled hole and have plastic fluid conduits.
peen in place on both sides of plate. Ensure plate will still fit flush on
both castings.
CAUTION: Failure to block orifice will result in No Movement of vehicle.

Packaging Pocket 4
• Drill Bit, .062" dia.
• Aluminum Plugs, .062" dia. (2) 1 extra
CAUTION: Use care when modifying the balance orifice.
Gaskets are bonded to the plates and damage could occur.

©2019 Sonnax Transmission Company, Inc. • A Marmon / Berkshire Hathaway Company 6T40-ZIP_Guide_E 07-12-19
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 GM 6T40 (Gen. 1), 6T45 (Gen.1),
6T50 (Gen. 1) ZIP KIT ®
PART NUMBER 6T40-ZIP INSTALLATION & TESTING BOOKLET

6T40 Generation 1 Figure 1 Valve Body Identification

Valve Body
Confirm Generation
This Zip Kit works in Generation 1 6T40 series valve bodies. To confirm core is a
Generation 1 versus a Generation 2, check for 4-5-6 clutch boost valve in control
valve body (Figures 1 & 2).

TCM
Also check the Transmission
6T40 Generation 2 Figure 2 Control Module (TCM) identi-
Control Valve Body Section
fications as shown in (Figures 3
& 4). The valve body and TCM
must have the same Generation.

Adaptive Learning
The 6T40, 6T45 and 6T50 are
Generation 1 - No 4-5-6 clutch boost valve equipped with several adaptive
Generation 2 - Has 4-5-6 clutch boost valve learning strategies. After valve
Figure 3
body service the existing adap-
TCM Identifier Figure 4
TCM tive values will need to be erased. Then, a “Fast Learn”
Generation 1 Number process should be performed. Reference GM material
Generation 2 Letter for proper “Fast Learn” process.

Solenoids
The Generation 1 6T40, 6T45 and 6T50 solenoids are Variable Bleed Type (VBS)
and cannot be interchanged with Generation 2 solenoids. These are calibrated at
TCM Identifier is 8th the factory and switching locations in the valve body should be avoided. Different
digit from left. suppliers were used, resulting in different solenoid plastic snout colors. Colors are
black, blue, yellow and natural.
Solenoid & Clutch Apply Chart Figure 5 Figure 6
Low Rev. 4-5-6
CL PC Sol 3 N.H.

1-2-3-4 Clutch
3-5 Rev. CL PC
1-2-3-4 CL PC

Low & Rev. CL

Shift Solenoid

4-5-6 Clutch

3-5 Reverse

Low & Rev.

2-6 Clutch
2-6 CL PC

Sol 2 N.H.
Sol 5 N.L.

Sol 4 N.L.

Clutch
Clutch

(OWC)

Range/Gear

Park On Off Off Off On Applied*

Reverse On Off Off On On Applied Applied

1
Neutral On Off Off Off On Applied*
2
1st 3
On On Off Off On Holding †
Applied Applied
Breaking 4
1. Line PCS 5
1st Off On Off Off Off Holding Applied
2. 2-6 PCS
2nd Off On On Off Off Applied Applied
6
3. 1-2-3-4 PCS 7
Drive

3rd Off On Off On Off Applied Applied 4. Shift Solenoid

4th Off On Off Off On Applied Applied 5. TCC PCS 6T40 Generation 1
6. 3-5 Reverse PCS Solenoid Locations
5th Off Off Off On On Applied Applied

6th Off Off On Off On Applied Applied 7. L/R 4-5-6 PCS

NOTE: For shift soleoinds, "ON" = solenoid energized (pressurized), "OFF" = solenoid de-energized • Pressure Control Solenoid (PCS) 3-5 ohms at 70oF
(no pressure). For pressure control (PC) solenoids, "ON" = pressurized, "OFF" = no pressure. *Applied
• Shift Solenoid 16-20 ohms at 70oF
with no load. †Holding but ineffective.

©2019 Sonnax Transmission Company, Inc. • A Marmon / Berkshire Hathaway Company 6T40-ZIP_Booklet_E 07-12-19
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 GM 6T40 (Gen. 1), 6T45 (Gen.1), Installation & Testing Booklet
6T50 (Gen. 1) ZIP KIT®

Figure 7 OSS
Connection
Zip Kit Instructions
1. Valve Body Removal from Case
a. Disconnect the input speed sensor, output speed sensor and shift position
B
B B B switch connectors from valve body.
B B
b. Remove the three control valve body bolts, 40.5mm long (Figure 7).
B
B B B B B c. Remove the 12 control valve body bolts, 105mm long (Figure 7).
Shift
A
A Position d. Remove the control solenoid valve assembly with TCM from valve body.
Switch
Connection e. Remove the nine control valve body bolts, 60mm long (Figure 8).
ISS A
Connection
f. Remove the two control valve body bolts, 53mm long (Figure 8).
g. Remove the valve body from the case.
Figure 8
D D 2. Installation
Install Zip Kit parts as shown on diagram of separate quick guide sheet included in
this Zip Kit. Sonnax recommends vacuum testing critical wear areas not covered
by this kit to determine whether additional Sonnax parts are required (see page 3).
C 3. Filter Plate & Pressure Switches (Figure 12)
C NOTE: Keep the filter plate clear from any solvents, as distortion to the seals could occur.
C C C
C C C a. Remove and replace the filter plate. The seals take a set and will leak if reused.
C
b. Examine the pressure switches and seals for damage or contamination. Fracture
or delamination of the pressure switch laminate disc can occur, requiring seal
Removal Bolts Figure 9
and laminate disc replacement.
Bolt Color Bolt Torque
Quantity
Code Length Specification 4. Valve Body Reinstall into Case
A Red 40.5mm 3 71 in-lb a. Install valve body into case and secure with (2x) 53mm and (9x) 60mm bolts
B Green 105mm 12 106 in-lb until finger-tight (Figure 8).
C Blue 60mm 9 106 in-lb b. Tighten to 106 in-lb of torque in the indicated sequence (Figure 10).
D Yellow 53mm 2 106 in-lb
c. Install control solenoid body to valve body with (12x) 105mm and (3x)
40.5mm bolts until finger-tight (Figure 7).
Figure 10 d. Tighten (12x) 105mm bolts to 106 in-lb of torque in the indicated sequence
4 5 (Figure 11).
e. Tighten the (3x) 40.5mm bolts to 71 in-lb torque in the indicated sequence.
f. Reconnect the input speed sensor, output speed sensor and shift position
switch connectors (Figure 7).
9
Four Pressure Switches Figure 12
3
8 2 11
10 6 7 NOTE: Valve body
1 shown is a Gen. 1
late (TCM Identifier
#3, Figure 4), which
Figure 11 contains the neutral
or white colored
11 pressure switch
8 4 6 plastic conduits.
2 10
Early Gen. 1 valve
12 9 1 7 bodies (TCM
5 3
Identifier #1 or #2,
13 Figure 4) do not
14 have these
conduits.
15 Filter Plate

07-12-19 6T40-ZIP_Booklet_E ©2019 Sonnax Transmission Company, Inc. • A Marmon / Berkshire Hathaway Company
Page 2 800-843-2600 • 802-463-9722 • F: 802-463-4059 • www.sonnax.com
 GM 6T40 (Gen. 1), 6T45 (Gen.1), Installation & Testing Booklet
6T50 (Gen. 1) ZIP KIT®

Installing Sonnax Pressure Cover Plate Figure 13

Switch Rebuild Kit

GM first generation 6T40, 6T45, and 6T50 transmissions often set
various trouble codes related to failures of fluid pressure switches
that are internal to the transmission control module (TCM). These
codes may be accompanied by shift irregularities such as slipping,
flares, harsh application, and bindups.
As time goes by, the laminated portions of the pressure switches
can breach, preventing normal switch operation. If more than one
switch breaks down, failsafe mode can be triggered. Solenoid
Body & TCM assembly
1. Disassembly
a. Remove retaining screws and detach
Figure 14 Figure 15
solenoid body cover plate (Figure 13). TCM


NOTE: Before installing Sonnax
pressure switch rebuild kit,
test switches to verify proper
electrical operation.
Place ohmmeter leads on each side of pres-
sure switch, outside of the rivet (Figure 14).
Switches are normally closed and should
read from about .5 to 10 ohms in their non-
operated state. Pressing on the switch opens
the contacts and should result in O.L. reading.
If these tests fail, test resistance again at the Solenoid
switch side, before the rivet; loose rivets can Body
cause circuit interruption. If testing is success-
ful, proceed with installation of Sonnax kit.
Figure 16
b. Separate solenoid body from TCM (Figure 15). Four pressure
switch laminate discs are now exposed on underside of TCM
(Figure 16).
c. Remove D-rings from switches and discard (Figure 17).
d. Using a pencil eraser dabbed with assembly gel, remove OE
laminate discs from switches and discard (Figure 18).

Figure 17 Figure 18

©2019 Sonnax Transmission Company, Inc. • A Marmon / Berkshire Hathaway Company 6T40-ZIP_Booklet_E 07-12-19
800-843-2600 • 802-463-9722 • F: 802-463-4059 • www.sonnax.com Page 3
 GM 6T40 (Gen. 1), 6T45 (Gen.1), Installation & Testing Booklet
6T50 (Gen. 1) ZIP KIT®
2. Installation & Assembly Figure 19
a. E nsure any dirt or debris is cleaned from switches before proceeding.
b. Place Sonnax laminate discs on switches.
c. Install Sonnax D-rings over laminate discs, flat side facing
down. D-rings have slight interference fit; ensure they fit snugly
into switch (Figure 19).
NOTE: Some solenoid bodies are equipped with plastic fluid conduits
(Figure 20). If so equipped, remove conduits to expose O-rings (Figure 21).
 Replace O-rings with Sonnax O-rings and reinstall conduits.

d. Reinstall solenoid body to TCM (Figure 22).

WARNING: Steps "e" and "f" apply only to units that DO NOT Place Sonnax laminate discs, then install D-rings flat side down.
have plastic fluid conduits.

e. With TCM still separated from the solenoid body, place Sonnax Figure 20
spacers over switches A dab of assembly lube will help keep them
in place during reassembly (Figure 23). These spacers assist in
keeping appropriate support on switches with over-flexed termi-
nals, which is vital to maintaining proper switch function.
 f. Use 6-32 screws and nut (not included) in eight locations
to securely attach cover plate to TCM housing (Figure 24).
Check for continuity of each pressure switch at the termi-
nals. Remove spacers from any switches indicating too
much preload (outside the .5 to 10 ohms range). Plastic fluid conduits equipped on some solenoid bodies.
WARNING: Do NOT install Sonnax spacers into units equipped WARNING: Do NOT install Sonnax spacers into units equipped
with plastic fluid conduits! with plastic fluid conduits!

g. Reinstall solenoid body cover plate and secure with retaining

Figure 22
screws (Figure 13).

Figure 21
TCM

Solenoid
Body

Lift plastic fluid conduits to expose O-rings.

Figure 23 Figure 24

Check
resistance
Place spacers at terminals.
here.

1 2 3

8
Cover Plate 5 6 7
4

07-12-19 6T40-ZIP_Booklet_E ©2019 Sonnax Transmission Company, Inc. • A Marmon / Berkshire Hathaway Company
Page 4 800-843-2600 • 802-463-9722 • F: 802-463-4059 • www.sonnax.com
 GM 6T40 (Gen. 1), 6T45 (Gen.1), Installation & Testing Booklet
6T50 (Gen. 1) ZIP KIT®

Critical Wear Areas & Vacuum Test Locations

NOTE: OE valves are shown in rest position and should be tested in rest position unless otherwise indicated. Test locations are pointed to with an arrow.
Springs are not shown for visual clarity. Low vacuum reading indicates wear and Sonnax parts noted for replacement.

Control Valve Body – Front • 6T40 Gen. 1 Shown Compensator Feed

*Plug port Regulator Valve
on back.
3-5 Reverse Clutch • Harsh shifts • Downshift clunk
*Plug port • Bump/Flare shifts • Bind-up
Regulator Valve on back.
• Overheated fluid • Burnt clutches
• Burnt 3-5 Reverse clutch
Replace with Sonnax Part No.
• Delayed Reverse
104740-09K*
• 3rd & 5th Shift concerns
• 2-3 & 4-5 Flare
 
2-6 Clutch
Regulator Valve
1-2-3-4 Clutch • Burnt 2-6 clutch
Regulator Valve • 2nd & 6th Shift concerns
• Burnt 1-2-3-4 clutch *Plug port • 1-2 & 5-6 Flare
• Delayed Forward on back.
• 1-2-3-4 Shift concerns
TCC Regulator


Apply Valve
1-2-3-4 Clutch • Code P0741, 742 • TCC slip
Boost Valve • No lockup • Harsh TCC apply
• Slip codes • Slips & flares • Loss of fuel economy
• Delayed engagement • Low TCC apply pressure


• 1-2-3-4 Clutch burned • Overheated fluid & TCC lining
• Shift quality is not load sensitive Replace with Sonnax Part No.
• Harsh/Slide shifts 144740-16K
Requires F-144740-TL16 & VB-FIX
Replace with Sonnax Part No.
144740-22
Requires F-144740-TL21 & VB-FIX
Clutch Select Valve
*Plug port • Various shift concerns
Low Reverse on back. • Shift codes
4-5-6 Clutch
Regulator Valve *Note: Plug casting valley with foam, putty
• Burnt L/R & 4-5-6 clutch or appropriately sized O-ring coated in
*Plug port assembly lube to isolate circuit.
• Delayed Reverse
on back.
• 4-5-6 Shift concerns
• 3-4 Flare Actuator Feed
Limit Valve
• No 4th, 5th or 6th
• Low clutch oil pressure
Control Valve Body – Back • Harsh/Flare shifts
Gen. 1 6T40 Shown Replace with Sonnax Part No.
144740-01 Requires 144740-TL

O-Ringed End Plugs

• Pressure loss • Burnt clutches
*Plug these ports (as
noted above) while • Shift concerns • TCC apply concerns
vacuum testing. NOTE: : Vacuum test end plugs at outboard
port while sealing bore opening with thumb.
Replace with Sonnax Part No.
144740-02K*
*Part numbers with an asterisk (*)
are included in this Zip Kit.
NOTE: Several Locations = 

©2019 Sonnax Transmission Company, Inc. • A Marmon / Berkshire Hathaway Company 6T40-ZIP_Booklet_E 07-12-19
800-843-2600 • 802-463-9722 • F: 802-463-4059 • www.sonnax.com Page 5
 GM 6T40 (Gen. 1), 6T45 (Gen.1), Installation & Testing Booklet
6T50 (Gen. 1) ZIP KIT®

Critical Wear Areas & Vacuum Test Locations

NOTE: OE valves are shown in rest position and should be tested in rest position unless otherwise indicated. Test locations are pointed to with an arrow.
Springs are not shown for visual clarity. Low vacuum reading indicates wear and Sonnax parts noted for replacement.

Pump Body • 6T40 Gen. 1 Shown

Pressure Regulator Valve

• Harsh/Soft shifts
• High/Low line pressure
• Burnt clutches
Replace with Sonnax Part No.
144510-01K Requires F-144510-TLC & VB-FIX

Plug casting valley with foam, putty

or appropriately sized O-ring coated
in assembly lube to isolate circuit.

TCC Control Valve

• Incorrect TCC apply/release
• Inadequate lube & cooling
• Transmission overheat
• Converter codes
Replace with Sonnax Part No.
144510-05K Requires F-144510-TL5C & VB-FIX

07-12-19 6T40-ZIP_Booklet_E ©2019 Sonnax Transmission Company, Inc. • A Marmon / Berkshire Hathaway Company
Page 6 800-843-2600 • 802-463-9722 • F: 802-463-4059 • www.sonnax.com
 GM 6T40 (Gen. 1), 6T45 (Gen.1), Installation & Testing Booklet
6T50 (Gen. 1) ZIP KIT®

OE Exploded View
Control Valve Body • 6T40 Gen. 1 Shown
NOTE: Depending upon vehicle application, the OE springs shown may not be present.

101
110

109

108 102

107

103

106 104

105

Control Valve Body Descriptions

I.D. No. Description

101 Compensator Feed Limit Valve
102 TCC Regulator Apply Valve
Clutch Select Valve (inboard)
103
Shuttle Valve (outboard)
104 Actuator Feed Limit Valve
105 Manual Valve
Reverse & 4-5-6 Clutch
106
Regulator Valve
107 1-2-3-4 Clutch Boost Valve
108 1-2-3-4 Clutch Regulator Valve
109 2-6 Clutch Regulator Valve
3-5 Reverse Clutch Regulator
110
Valve

©2019 Sonnax Transmission Company, Inc. • A Marmon / Berkshire Hathaway Company 6T40-ZIP_Booklet_E 07-12-19
800-843-2600 • 802-463-9722 • F: 802-463-4059 • www.sonnax.com Page 7
 GM 6T40 (Gen. 1), 6T45 (Gen.1), Installation & Testing Booklet
6T50 (Gen. 1) ZIP KIT®

OE Exploded View
Pump Body • 6T40 Gen. 1 Shown
NOTE: Depending upon vehicle application, the OE springs shown may not be present.

201

202

Pump Body Descriptions

I.D. No. Description

201 Line Pressure Relief Ball
202 Pressure Regulator Valve
203 TCC Control Valve
204 TCC Relief Ball
204

203

07-12-19 6T40-ZIP_Booklet_E ©2019 Sonnax Transmission Company, Inc. • A Marmon / Berkshire Hathaway Company
Page 8 800-843-2600 • 802-463-9722 • F: 802-463-4059 • www.sonnax.com