SIL 34­EP­16
July, 2016
Page 1 of 4
SUBJECT:

Replacing the AC Choke on Dual Power Inverter Module 2 (DPIM2)

MODELS AFFECTED:

H 40/50 EPTM System Equipped with DPIM2

Tools Required:
• Torx­Plus® T20 Bit

Introduction:
This Service Information Letter (SIL) announces the availability of service parts (refer to Table 1) to replace the
AC choke and O­ring mounted to the DPIM2 (refer to Figure 1). The service parts will remedy the following issues:
• Stripped/broken high voltage cable flange threads
• Damaged/corroded O­ring sealing surfaces
• Damaged AC choke and/or housing
• Damaged plastic sleeve through choke

Figure 1. AC Choke (Typical)
NOTE: This procedure may eliminate the need for a complete DPIM2 replacement under certain failure
conditions.
The service parts table below will service one AC Choke, if both require service you must double the
quantity shown (refer to Table 1).

ML / SL7878EN

3349948

Copyright © 2016 Allison Transmission, Inc. All Rights Reserved.

SIL 34­EP­16
July, 2016
Page 2 of 4
Table 1. AC Choke Service Parts (Refer to Figure 2)
Item Number

Part Name

Part Number

Quantity

1

Screw, M4x14mm

29540721

10

2

O­Ring, EMI

29540716

1

3

AC Choke Assembly

29546996

1

Figure 2. AC Choke Service Parts
NOTE: The Electrical Disconnect Verification Procedure MUST be performed prior to attempting the
AC choke replacement.

WARNING: DO NOT rely on the High Voltage Interlock Loop (HVIL) or control systems to de­energize
the system. Always perform the Electrical Disconnect Verification Procedure to be sure the system is
discharged before servicing components.
DO NOT attempt to bypass any High Voltage Interlock for any reason. Tampering with the HVIL may result
in injury. Failure to follow proper safety procedures may result in serious personal injury or death.

Copyright © 2016 Allison Transmission, Inc. All Rights Reserved.

SIL 34­EP­16
July, 2016
Page 3 of 4
AC Choke Removal:
1. Using a Torx­Plus® T20 bit, remove the ten (10) M4x14mm screws that secure the AC choke to the main
chassis of the DPIM2 (refer to Figure 3).

Figure 3. AC Choke Screws
2. Remove and discard the O­ring from the main DPIM2 chassis. Clean the O­ring groove of any debris. Clean
the mounting face of the chassis of any debris and/or light corrosion.
AC Choke Installation:
1. Install a new O­ring into the groove ensuring it is not stretched or torn and is fully seated in the groove
(refer to Figure 4).
NOTE: The EMI gasket must always be replaced when the AC choke is separated from the chassis.

Copyright © 2016 Allison Transmission, Inc. All Rights Reserved.

SIL 34­EP­16
July, 2016
Page 4 of 4

Figure 4. Gasket Installation
2. Position the AC choke against the DPIM2 chassis ensuring the circled reliefs in the rubber insert are on
top (refer to Figure 5).

Figure 5. Relief in Rubber Insert on Top
Torx­Plus®

3. Using a
T20 bit, install the ten new (10) M4x14mm screws that secure the AC choke to the main
chassis of the DPIM2 (refer Figure 3). Torque the ten (10) M4x14mm screws to 1.2­1.5 N∙m (10.6­13.3 lb in.).
NOTE: For additional information refer to H 40/50 EPTM System Service Manual SM3602EN Appendix E

Copyright © 2016 Allison Transmission, Inc. All Rights Reserved.