29541991 | Genuine Allison® Transmission Push Button Shift Selector

1. Ease of Use

• No manual shifter to move—just press a button to select Drive, Neutral, or Reverse.

• Especially useful for fleet drivers, bus operators, or inexperienced drivers.

2. Reduced Driver Fatigue

• Requires less effort and physical movement than a lever or column shifter.

• Improves ergonomics in large vehicles where the cabin layout may vary.

3. More Accurate Gear Selection

• Buttons prevent mis-shifting, which can happen with manual or mechanical selectors.

• Gear selection is done through digital signals, reducing human error.

4. Electronic Integration

• Works with the vehicle’s electronic transmission control system (TCM).

• Can be integrated with other systems:

  • Brake interlocks (must press brake before shifting to Drive)

  • Engine control systems (to reduce load on the engine when shifting)

5. Space Saving

• No bulky shift levers—just a compact button panel.

• Frees up dashboard or console space in tight cabs.

6. Fewer Mechanical Parts

• No cables or linkages that can stretch, break, or require adjustment.

• Improves long-term reliability and reduces maintenance.

7. Safety Features

• Some systems prevent shifting into Reverse or Park unless the vehicle is at a stop.

• Protects the transmission from damage caused by accidental or incorrect shifts.

1. Won’t Shift into Gear

• Pressing buttons does nothing—no response from the transmission.

• Vehicle stuck in Neutral, Drive, or Park.

2. Incorrect Gear Selection

• Pressing "Drive" might shift into "Neutral" or nothing at all.

• Selector lights up the wrong gear or none at all.

3. No Lights / Display Malfunction

• Gear indicator lights don’t illuminate or flicker.

• LED screen (if present) is blank, dim, or shows error messages (like “--” or “S” for service mode).

4. Delayed Response

• Noticeable delay between pressing a button and the gear change happening.

• Especially dangerous when needing quick shifts, like from Reverse to Drive.

5. Intermittent Operation

• Sometimes it works fine, other times it doesn't—can indicate failing electrical contacts, corroded wiring, or a dying selector unit.

6. Error Codes from TCM

• Diagnostic scan reveals transmission-related fault codes like:

  • P0705 – Transmission Range Sensor Circuit Malfunction

  • P0880 – TCM Power Input Signal

  • Allison-specific codes like D1, D2, or S on the selector screen.

7. Locked in Limp Mode

• Transmission goes into "limp mode" (only 1st or 3rd gear available) to protect itself.

• Often caused by selector, wiring, or TCM communication issues.

8. No Communication with TCM

• Selector may fail to send signals to the Transmission Control Module (TCM).

• Could be due to internal failure, power loss, or wiring fault.