INSTRUCTION SHEET NO. 367
P/N 29565591
December 07, 2020
Page 1 of 6
SUBJECT:

Retarder Air Accumulator—Installation of Piston and Seals

MODELS AFFECTED:

All 3000/4000 Series

Use this instruction sheet to help select the appropriate end cap O-rings, and to help in the assembly process.
Table 1. Accumulator Seal Kits
Part Name (indented indicates content)

Qty

P/N

1

29563811

Piston Lip Seal

2

29563171

Sealring (Slide Ring)

1

29527009

End Cap O-ring (Aluminum)

2

29534489

1

29565564

Instruction Sheet #367

1

29565591

Sealring (Slide Ring)

1

29527009

Piston Lip Seal

2

29563171

Piston (A)

1

29564913

End Cap O-ring (Aluminum)

2

29534489

End Cap O-ring (Steel)

2

29527010

Nipple With Sealant

1

29563216

Seal Kit

Seal, Piston, Nipple Conversion Kit

NOTE: Use Seal Kit P/N 29565564 to convert former TID 1, 2, 3 or TID A, B accumulators to current
configuration accumulator. Former accumulator designs include P/Ns 29534483 and 29544596 (3000
Series) and 29534484 and 29544648 (4000 Series). Use Seal Kit P/N 29563811 to service current
configuration accumulator.

MC / IS8517EN

5184976

Copyright © 2020 Allison Transmission, Inc. All Rights Reserved.

INSTRUCTION SHEET NO. 367
P/N 29565591
December 07, 2020
Page 2 of 6

Figure 1. Parts Used to Assemble Cylinder
Table 2. Figure 1 Legend
Reference Number

Part

1

Concave Side of Piston Facing Air Side End Cap

2

Air Side End Cap

3, 8

O-ring

4, 7

Seal, Lip

5, 10

Piston (A) on Fluid Side Face

6

Sealring

9

Fluid Side End Cap

WARNING: Relieve residual air pressure from the vehicle air system to the inlet side of the accumulator
air solenoid valve prior to disconnecting air supply to remove the accumulator from the vehicle.

NOTE: The concave/cupped side of the piston faces the air solenoid valve end cap in all accumulator
models. Lightly lubricate piston seals with clean transmission fluid just prior to installation into the
accumulator cylinder. Verify cleanliness of all components prior to assembly. If uncertain of end cap
material, check with a magnet to determine if aluminum or steel, then use Table 1 to select the proper
end cap O-rings.
1. Install the piston (A) into the cylinder bore with one lip seal groove exposed.
Copyright © 2020 Allison Transmission, Inc. All Rights Reserved.

INSTRUCTION SHEET NO. 367
P/N 29565591
December 07, 2020
Page 3 of 6
2. Install a piston lip seal on the piston, larger outside diameter section of taper facing outward (refer to
Figure 2 and Figure 3).

Figure 2. Piston Lip Seal Orientations
Table 3. Figure 2 Legend
Reference Number

Part

4, 7

Seal-Larger Outside Diameter Section of Taper Facing Outward

Figure 3.
3. Press the piston and seal through the bore, being careful not to damage or roll the installed piston lip
seal. Press until you expose the piston at the opposite end while leaving the first seal inside the cylinder
bore (refer to Figure 3). Install the second piston lip seal, larger outside diameter section of taper facing
outward, and install the sealring (refer to Figure 4).

Copyright © 2020 Allison Transmission, Inc. All Rights Reserved.

INSTRUCTION SHEET NO. 367
P/N 29565591
December 07, 2020
Page 4 of 6

Figure 4.
4. Press the piston assembly back into bore. Be careful not to roll or damage the installed piston lip seals.
Lubricate again, if needed, before moving the piston fully into the cylinder (refer to Figure 5).

Figure 5.
5. Install the O-ring seal inside the air solenoid valve side end cap. Install the air side end cap on the concave
side of the piston (refer to Figure 6).

Figure 6. Air Side End Cap Partially Transparent – Showing Concave Side of Piston
Copyright © 2020 Allison Transmission, Inc. All Rights Reserved.

INSTRUCTION SHEET NO. 367
P/N 29565591
December 07, 2020
Page 5 of 6
Table 4. Figure 6 Legend
Reference Number

Part

1

Air Side End Cap

2

Fluid Side End Cap

6. Install the O-ring seal inside the fluid side end cap (refer to Figure 6). Install the fluid side end cap and O-ring
seal on the cylinder. Install the appropriate O-ring seal on the air side end cap. Install the air side end cap
and O-ring on the cylinder. Install the 4 bolts through the air side end cap into the threaded fluid side end cap
and torque the bolts to 32–36 N∙m (24–27 ft-lb). Run the bolts to contact first, then tighten fully in a cross
pattern. Visually inspect both ends of the assembly to ensure the O-ring seals are not visible at either end.
When replacing the air solenoid valve nipple:
1. Install the nipple with pre-applied sealant into the air solenoid valve.
2. Tighten air solenoid-to-accumulator nipple fitting (P/N 29563216) to 13 N∙m (10 lb-ft).
3. Install air solenoid valve and nipple assembly into the accumulator end cap.
4. For 4000R or B500R, tighten air solenoid-to-air line nipple fitting with orifice (P/N 29566363) to 13 N∙m (10
lb-ft).
5. Continue rotating solenoid until desired orientation is achieved (not to rotate over 360 deg after initial 13 N∙m
(10 lb-ft) torque is obtained).
NOTE: The nipple may be reused if sealant is applied.

Figure 7. Accumulator Assembly
Table 5. Figure 7 Legend
Reference Number

Part

1

Nipple with Sealant and Orifice (fitting has “HD” marking and green paint to distinguish
it from item 3)
Copyright © 2020 Allison Transmission, Inc. All Rights Reserved.

INSTRUCTION SHEET NO. 367
P/N 29565591
December 07, 2020
Page 6 of 6
Table 5. Figure 7 Legend (cont'd)
Reference Number

Part

2

Air Solenoid Valve

3

Nipple with Sealant

4

Accumulator

Copyright © 2020 Allison Transmission, Inc. All Rights Reserved.