Cause and Solution for Allison Transmission No Forward or Reverse Gear

Vehicles that stall and cannot move forward or reverse have significant transmission problems.

Sometimes the vehicle moves forward without reversing or reverses without going forward.

With a few minor differences, these 02 problems have almost similar causes.

This article explains these problems separately, along with their causes and solutions.

Read also:

Allison Transmission No Forward Or Reverse Gear [Causes, Symptoms and Solution]

07 Factors cause Allison transmission no forward or reverse gear, including incorrect gear, blown transmission, dirty or low transmission fluid etc.

These 07 factors are:

  1. The vehicle may not be in the correct gear
  2. Transmission might be blown
  3. The air-fuel ratio may be incorrect
  4. Dirty transmission fluid
  5. Very low-level transmission fluid
  6. Shifter mechanism problems
  7. Problems with ECU (Electric Control Module)

These problems are caused by Allison transmission, no forward or reverse gear.

But sometimes, the transmission won’t go forward but reverse or the opposite.

Usually, the problems listed above are the causes.

But there is very little difference between forward and reverse issues.

Causes of Allison Transmission No Forward Gears

Causes of Allison Transmission No Forward Gears

Whenever there is a problem with a vehicle, it should be addressed immediately.

A transmission with no forward gear is a major problem.

The possible causes of Allison’s transmission having no forward gear but will reverse are given below.

There are some reasons why cars will not move forward but reverse.

Damaged or incorrect transmission components can cause no forward problems, especially automatic transmissions.

The transmission problem is the main reason a vehicle won’t go forward or reverse.

01. Cracked Fluid Tube

If the fluid tube is cracked or broken, it may cause no forward movement.

If the forward fluid tube cracks, fluid leaks, and the vehicle reverse instead of going forward.

Replacing the part is the right solution.

02. Transmission Fluid

Forward gear problems may occur if the transmission fluid is low or dirty.

So it is important to maintain an appropriate fluid level.

03. Speed Sensor

A speed sensor is a tiny component of a vehicle’s transmission system.

If the sensor is damaged or faulty, many problems arise.

No forward transmission is one of them.

Symptoms of Allison Transmission No Forward Gears

There are 05 symptoms of no forward gear:

  1. Grinding and shaking
  2. Fluid leaks
  3. Burning smell
  4. Won’t shift into gear
  5. The car shifts into limp mode

Solution to Allison Transmission No Forward Gears

You should identify the causes and determine why transmission is not working.

Then follow these 05 steps:

  1. Check the gear; if it is in the neutral position, change it
  2. Fill the fluid level if it is low; check it regularly
  3. Replace the fluid tube if it is cracked
  4. Replace the speed sensor if it is damaged
  5. Whenever you notice problems with the inner parts of the transmission, consult a professional mechanic.

Cause of Allison Transmission No Reverse Gears

The reverse gear is usually the first gear to fail when there is a problem with the transmission system.

The reverse gear may not work properly if you are parking in a garage or parking lot.

When the reverse gear isn’t working, a dangerous situation may occur.

In other words, it involves the safety of your driving.

So, make sure the reverse gear works before driving.

04 different reasons usually cause reverse gear problems.

Few problems are easy to fix, but some require the services of a qualified mechanic.

Here are the reasons:

Cause of Allison Transmission No Reverse Gears

01. Faulty Transmission Selector Sensor

To activate the reverse gear, the control module needs a sensor signal.

A faulty transmission selector sensor may prevent the signal from being transmitted, resulting in a check engine light.

Faulty transmission selector sensors cause both forward and reverse gear problems.

02. Transmission Fluid Level

An engine can overheat if the fluid level is low, preventing the reverse gear from working.

The same problem occurs with dirty fluids.

Transmission fluid should be changed every 25,500 miles or 41,038 kilometers.

03. Broken Teeth

No reverse gear problem occurs if the reverse gear teeth are broken.

In addition to manual transmissions, it also affects Allison automatic transmissions.

04. Wrong Shift Mechanisms

An Allison transmission switch fails to get an accurate signal if there is a problem with the engine control module (ECM) or sensor connections.

And it causes no gear problem.

Symptoms of Allison Transmission No Reverse Gears

08 Symptoms of the No reverse gear include the following:

  1. The vehicle fails to shift to park mode
  2. The car goes into limp mode in a single gear
  3. Inaccurate vehicle transmission shifting
  4. Whining, grinding noise from the transmission when trying to reverse mode
  5. Gears begin to slip
  6. Engine overheating
  7. Hard to switch to reverse mode
  8. You can’t change gears once your vehicle is in reverse.

Solution to Allison Transmission No Reverse Gears

The following steps must be taken to solve the no reverse gear issue:

  1. Check the transmission fluid; if it is dirty, drain it and refill it with the correct fluid. You can follow the owner’s manual to identify the appropriate fluid.
  2. Check the fluid level, and ensure it is at the required level.
  3. Check and replace the faulty sensors.
  4. If the reverse gear teeth have been broken, replace the teeth. It is a complicated procedure, so hiring a skilled mechanic is better.
  5. If there is a problem with the shift mechanism, take your vehicle to the dealership to check your ECM. They will fit it properly and resolve the issue.

The following video will help you to solve the no reverse gear issue

How Much Does It Cost to Rebuild an Allison 1000?

Rebuilding an Allison 1000 is a time-consuming and expensive project.

Since rebuilding includes inspecting, cleaning, and replacing defective parts, an Allison rebuild will cost between $2,000 and $5,000.


What would cause an Allison Transmission to not shift in gear?

The reasons that cause Allison transmission not to change gear are:

  • Transmission sleep
  • Dirt or debris in the transmission fluid
  • Low transmission fluid
  • Wrong air-fuel mixture.

How do I know if my Allison Transmission is bad?

Some symptoms indicate Allison transmission is bad.

The symptoms are:

  • Leaks
  • Delay response or no response gear
  • Grinding or clunking noise while shifting gears
  • Check engine light appears sometimes
  • Engine overheating is a probable symptom

These are the signs of your transmission going out.

Can a clogged transmission filter cause no reverse?

Yes. When the transmission filter gets clogged, it causes difficulty in the reverse gear.

A clogged transmission filter causes a slipping transmission, shifting problems, grinding gears, and other possible symptoms of transmission issues.

Can A Dirty Transmission Fluid Cause No Reverse?

When transmission fluid gets dirty, it fails to flow smoothly.

Dirty transmission fluid fails to lubricate the transmission parts properly.

That’s why cars cannot shift into reverse.

Can a speed sensor cause no reverse?

Yes, the speed sensor sends signals to the transmission to shift the gears.

When a false signal comes from the speed sensor, the power control module will fail to control the gears correctly, and there will be no reverse problem.

So, faulty speed sensors need to be replaced.


Vehicle transmission is the most complex component.

The cost of repairing or replacing a transmission is high.

Therefore, it is crucial to identify the possible causes of the no forward or no reverse problem before trying to fix it.

Problems can sometimes be fixed with a simple repair.

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