Revisions to this document are noted
by a stripe in the left-hand margin

SUBJECT:

SIL 21-1K2K-21, Rev. B
April 26, 2023
Page 1 of 7

MY2022 Coordinated Front End Changes

MODELS AFFECTED:

1000 SeriesTM and 2000 SeriesTM, 6-Speed

SERIAL NUMBERS AFFECTED:

Beginning with S/N 6312000386 (Indianapolis) and S/N 6330076304
(Chennai).

Introduction:
In an effort to commonize parts toward the production of 1000 Series and 2000 Series 6-Speed and the 9-Speed
transmissions, Allison Transmission has implemented a series of changes to the 1000 Series and 2000 Series
6-Speed products.
Coordinated design changes were introduced in January 2022 and primarily focused on changes to the front end of
the 1000 Series and 2000 Series 6-Speed transmissions. Changes to the turbine shaft, ground sleeve and torque
converter turbine hub were timed together. Additional changes to the valve body separator plates and shaft seal
rings will follow. All changes described in this SIL will follow the serial number break points listed above.

Part Changes:
To achieve the desired torque capabilities of the 9-Speed, the turbine shaft diameters and transition radii changed
in multiple locations across its length. The current turbine shaft (P/N 29563898) used in the 1000 Series and 2000
Series 6-Speed, as well as the 9-Speed, contains a hub seal surface on the front end, along with an additional front
spline. The current turbine shaft splines will contain 26 teeth, whereas the former turbine shaft (P/N 29557844
and earlier) contain 25 teeth. Refer to Figure 1 for turbine shaft comparisons and Figure 2 for the current turbine
shaft hub seal interface.

JT / SL8924EN

6506214

Copyright © 2022 Allison Transmission, Inc. All Rights Reserved.

SIL 21-1K2K-21, Rev. B
April 26, 2023
Page 2 of 7

Figure 1. Former and Current Turbine Shaft Features

Figure 2. Current Turbine Shaft and Turbine Hub Seal Interface
Lockup pressure sealing has moved from the front ground sleeve seal ring to the current torque converter and
turbine hub seal design as shown in Figure 2. Current torque converter engineering groups (21-985, 21-986,
21-987, 21-988, 21-989, 21-990 and 21-991) have been released and contain the current turbine hub, hub splines
and turbine hub seal. New torque converter assembly part numbers have been released and are shown in Table 1.
Former torque converter assembly part numbers will remain available for service but are not compatible with the
MY2022 Coordinated Front End design.

Copyright © 2022 Allison Transmission, Inc. All Rights Reserved.

SIL 21-1K2K-21, Rev. B
April 26, 2023
Page 3 of 7
Table 1. Former and Current Groups and Associated Part Number for Torque Converter Assemblies
Former

Current

Group #

TC Assy P/N

Description

Group #

TC Assy P/N

Description

21–950

29546574

TC210

21–985

29564108

TC210

21–949

29546573

TC211

21–986

29564107

TC211

21–951

29546576

TC221

21–987

29564109

TC221

21–952

29546575

TC222

21–988

29564110

TC222

21–966

29556904

TC211D

21–989

29564111

TC211D

21–967

29556905

TC221D

21–990

29564112

TC221D

21–968

29556906

TC222D

21–991

29564113

TC222D

Changes to the turbine shaft drove changes to the ground sleeve and to the torque converter internal interface with
shafts and sealing surfaces. In particular, the current ground sleeve (P/N 29563907) has been shortened over
the former ground sleeve (P/N 29546283) by removing the front seal ring and seal ring groove. Additionally, the
rear-most lube hole diameter has been increased from 4.0 mm to 6.0 mm. The former front ground sleeve seal has
been replaced by a turbine shaft hub seal within the torque converter as shown in Figure 2. Refer to Figure 3 for
ground sleeve comparisons. Similar to the former torque converter assembly part numbers, former turbine shaft
and ground sleeve assembly part numbers will remain available for service.

Figure 3. Former and Current Ground Sleeves

Compatibility of Parts:
The coordinated changes found within the front support and rotating clutch assemblies are not backward
compatible, and parts of the current design cannot be intermixed with prior designs. For these changes which
occurred in the front support and rotating clutch assemblies, all new part numbers and engineering group
numbers were released to help prevent intermixing. The additional tooth of the current turbine shaft front spline
area also prevents misassembly. Refer to Table 2 for current part numbers and group numbers associated with
these changes.

Copyright © 2022 Allison Transmission, Inc. All Rights Reserved.

SIL 21-1K2K-21, Rev. B
April 26, 2023
Page 4 of 7
Table 2. Former and Current P/Ns and Group Numbers
Part Description

Former P/N

Current P/N

10–674

10–676

_Support Assembly-Front

29564880

29563908

__Support Assembly-Front, with Ground Sleeve and Bearing

29564881

29563909

___Support Assembly-Front, with Ground Sleeve

29564882

29563910

____Sleeve Assembly-Ground, with Bushing

29546302

29563906

_____Sleeve-Ground, Shaft

29546283

29563907

_Sealring-External Butt Joint (front groove location)

29538158

Oil Pump Group-Standard

14–1114

14–1144

_Clutch & Shaft Assembly-Rotating, PTO

29546281

29564120

__Shaft Assembly-Turbine

29558949

29563897

___Shaft-Turbine*

29557844

29563898

__Sealring-Rotating, 45.5mm 2L Joint (2 pcs)

29538158

29558601

__Gear-Sun, P1

29537433

29562300

_Bearing-Thrust, Roller, T3

29531095

29558605

14–1115

14–1145

_Clutch & Shaft Assembly-Rotating, with Tone**

29546282

29564115

__Shaft Assembly-Turbine

29558949

29563897

___Shaft-Turbine*

29557844

29563898

__Sealring-Rotating, 45.5mm 2L Joint (2 pcs)

29538158

29558601

__Gear-Sun, P1

29537433

29562300

_Bearing-Thrust, Roller, T3

29531095

29558605

Planetary Gear Group-PTO**

Planetary Gear Group-Non PTO

* Serviced only as an assembly — Not available as a detailed part.
** Not serviced as an assembly — Order detail parts

Copyright © 2022 Allison Transmission, Inc. All Rights Reserved.

SIL 21-1K2K-21, Rev. B
April 26, 2023
Page 5 of 7

Figure 4. Current Front Support & Bearing Assembly (P/N 29563909)
The turbine shaft seal ring design has changed from a butt joint to a 2L lap joint which improves sealing
consistency. The current seal ring (P/N 29558601) shown in Figure 5 replaces the former seal ring (P/N 29538158)
and is backward compatible with former turbine shaft designs. As such, the former seal ring has been completely
cancelled, stock has been exhausted and replaced by the current seal ring for future service needs. Seal ring sub
kit (P/N 29536405) which contains three pieces of former seal ring (P/N 29538158) is also completely cancelled,
but will remain available until the stock is depleted.
Seal and gasket kits are being updated to include the current seal ring (P/N 29558601). Service kit part numbers
(P/N 29545311, P/N 29545312 and P/N 29547606) will remain the same. Newly assembled kits will no longer
contain a separate, sealed bag with the former seal rings (sub-kit P/N 29536405). Instead, the seal and gasket kits
will contain three loose seal rings (P/N 29558601).
NOTE: Due to its material properties, the current seal ring (P/N 29558601) does not need to be in a
sealed bag.

Figure 5. Current Turbine Shaft Seal Ring and Location

Copyright © 2022 Allison Transmission, Inc. All Rights Reserved.

SIL 21-1K2K-21, Rev. B
April 26, 2023
Page 6 of 7
A change to the control main valve body separator plate was also needed. With the changes to the 1000 Series
and 2000 Series, 6-Speed transmission front end design, comes changes to its internal fluid dynamics. The
torque converter clutch (TCC) exhaust backfill orifice found in former separator plates had to increase to maintain
lockup release times. The exhaust backfill orifice in the current separator plates (identified in Figure 6 below) has
been increased from 3.0 mm to 6.0 mm in diameter. This increased diameter TCC exhaust backfill orifice is a
running change to existing engineering groups 16-1902 and 16-1904 since the current separator plates are
backward compatible. The current separator plate for the NAS control module assembly (P/N 29568757) replaces
P/N 29553154. Similarly, the current separator plate for the TCC High Gain, Non-NAS control module assembly
(P/N 29568756) replaces P/N 29553484.
WARNING: Former separator plates (P/N 29553154, P/N 29553484 and earlier with 3.0mm TCC backfill
exhaust diameter orifice) are NOT forward compatible. Care must be taken in selecting the correct
separator plate for transmissions with coordinated front end changes mentioned in this SIL.

NOTE: The last 4 digits of separator plate part number is stamped on each plate for identification.

Figure 6. Example of the Enlarged TCC Exhaust Backfill Orifice in the Separator Plate
The MY2022 Coordinated Front End Changes described in this SIL make up a unique design of the 1000 Series
and 2000 Series 6-Speed transmission. With the exception of the current seal ring (P/N 29558601) and current
separator plates (P/N 29568756 and P/N 29568757), current parts mentioned in this SIL are NOT backward
compatible with transmission designs prior to the serial number break points listed on page 1, or with former
engineering groups (i.e. 10-674, 14-1114, 14-1115 and earlier).
Follow the appropriate 1000 Series and 2000 Series Parts Catalog to determine compatibility of parts and
respective part numbers. Use 1000 Series and 2000 Series Service Manual for proper overhaul practices, part
orientation and torque specifications.

Copyright © 2022 Allison Transmission, Inc. All Rights Reserved.

SIL 21-1K2K-21, Rev. B
April 26, 2023
Page 7 of 7

Service Parts:
The former part numbers found in Table 3 will be completely cancelled for service upon exhausting inventory at
Allison Parts Distribution Centers. In these cases, the current part numbers that are cross referenced can be used
to update the transmission with the former design since the current parts are backward compatible.
NOTE: When changing the design of an existing transmission, technicians must follow compatibility rules
found within this document.

Table 3. Cross Reference of Serviceable Part Numbers
Part Description

Former P/N

Current P/N

Seal Ring

29538158

29558601

Seal Ring, Sub-Kit (3pcs-29538158)

29536405

N/A

Separator Plate, NAS

29553154

29568757

Separator Plate, High Gain, Non-NAS

29553484

29568756

Copyright © 2022 Allison Transmission, Inc. All Rights Reserved.