Allison Transmission Relay Box 24 Volt 29556644 Front View
Allison Transmission 29556644 VIM (Vehicle Interface Module) superseded part 29509886 - Image 2
Allison Transmission 29556644 VIM (Vehicle Interface Module) superseded part 29509886 - Image 3
Allison Transmission Vehicle Interface Module (VIM) part 29509886
Allison Transmission Relay Box 24 Volt 29556644 Plug View

Allison Transmission 29556644 VIM (Vehicle Interface Module) superseded part 29509886

Code: 29556644-R

Allison VIM 29556644 Reman 12/24 Volt Vehicle Interface Module

Reaction Force LLC provides FREE BENCH TESTING and over-the-phone diagnostics. Questions about your Allison part? Call us today at (503) 862-6322.

Condition: Reman

Recalibration: Included

Compatible years: 1991-2006 both WTEC 2 and WTEC 3 generations

Warranty: 6 months

$699.00

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Description

Allison VIM 29556644 – 12/24 Volt Vehicle Interface Module

Compatible years: 1991-2006 both WTEC 2 and WTEC 3 generations

The Allison 29556644 is a 12 or 24-volt Vehicle Interface Module (VIM) unit that serves as a critical electrical gateway, linking the TCM with other vehicle systems like ignition, sensors, and the shift selector.

This is a reman VIM is fully compatible with most vocational, commercial, and fleet applications using Allison 1000–4000 Series transmissions.

Superseded part number: 29556644, 29509886

Common symptoms of a bad VIM

  • TCM has no power or will not respond

  • No shift pad activity or gear selection

  • Blown fuses related to the transmission system

  • Intermittent communication or limp mode

  • Codes such as U0101, P0880, or power supply faults

Because the VIM is a central electrical hub, failures can cause erratic or total loss of transmission control, even if the TCM and shift selector are still functional.

Pre-replacement checklist

Before replacing your VIM, inspect the following:

  1. 12V or 24V power supply and ground – Confirm clean, stable power

  2. Connector pins and terminals – Look for corrosion or bent pins

  3. Harness continuity – Ensure no broken or shorted wires

  4. Scan for TCM-related communication codes

  5. Confirm voltage output to shift selector and TCM

Reaction Force offers free phone diagnostics and advice to confirm if your VIM is the root cause.

Related diagnostic trouble codes

These fault codes may appear when the VIM is failing or not supplying proper power/communication:

  • U0101 – Lost communication with TCM

  • P0880 – TCM power input signal fault

  • P2534 – Ignition run/start circuit fault

  • P2544 – Torque management request input fault

  • P0562 – System voltage too low

If these appear and battery voltage is within spec, the VIM should be tested or replaced.

Installation notes

  • Disconnect battery before installation

  • Mount securely in dash with factory hardware

  • Connect wiring harness securely—check pins for damage or corrosion

  • If necessary, program the selector via TCM software after install

  • Clear any stored codes and verify proper display function before road test

Need help?

Reaction Force offers:

  • Free over-the-phone troubleshooting

  • Help confirming whether the VIM, TCM, or selector is to blame

  • Wiring diagram assistance and power flow testing advice

Call (503) 862-6322

Name

Images are for representation purposes only. For reman and RTO purchases a photo of the actual item you are receiving will be sent for approval prior to shipping.

Please see our warranty, shipping, refund, and return policies.

Frequently asked questions

1. What does the 29509886 VIM do?
It connects the transmission control system to vehicle power, ignition, and communication systems.

2. What systems use this VIM?
School buses, fire trucks, utility vehicles, and more.

3. Can I install it myself?
Yes, but you should have access to basic diagnostic tools and know how to verify voltage, ground, and continuity.

4. What’s the warranty on this part?
30-day exchange for functional failure. See our return policy for details.

5. What if this doesn’t solve my issue?
We’ll help you diagnose it—Reaction Force supports every sale with free troubleshooting to ensure you get what you need.

Additional information

Weight 3 lbs
Dimensions 9 × 9 × 4 in
Applications for 29509886

VIM (Vehicle Interface Module) is compatible with: 1000 Series 2000 Series 3000 Series 4000 Series
Common vehicles

Fire trucks and emergency response vehicles School buses and transit buses Refuse trucks and municipal vehicles RVs, step vans, and utility trucks Shuttle buses and box trucks with Gen 4/5 controllers Note: This 12V version is not compatible with 24V systems typically found in military or export applications.
Product specifications

Part number: 29509886 Type: Vehicle Interface Module (VIM) System voltage: 12V Compatibility: 1991-2006 both WTEC 2 and WTEC 3 generations Condition: Good (used), pulled from operational units

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