What to Do When Your Allison Transmission Won’t Go Into Gear

This indicates an issue with the Allison transmission, and it may require servicing to repair it.

Allison Transmission Not Going Into Gear

A major issue that can arise with Allison transmissions is when they wont go into gear. This issue can arise suddenly and, if not addressed properly and quickly, lead to permanent damage to the transmission. Those familiar with diagnosing and repairing Allison transmissions have expertise to identify potential causes and make any necessary repairs. Common issues include a faulty shift solenoid, insufficient fluid pressure or a broken input clutch hub. However, there are many other potential causes of the transmission not engaging properly.

Good diagnostics requires comprehensive knowledge and experience with Allison transmissions, such as the four stages of operation, torque converter clutch actuation, manual shift valve operation, filter service procedures and lube oil system function. The diagnostician needs to first inspect accessible components for obvious problems such as loose connections or damage. In most cases, component replacement or repair is necessary depending on the diagnosis. Any malfunction in the electronic control module prevents shifting; therefore accurate diagnostics is key to determining whether component replacement or module reprogramming is needed.

Properly functioning Allison transmissions are complex pieces of machinery that require expertise for troubleshooting when they fail to shift properly into gear. The challenge arises when trying to accurately diagnose the exact cause in order to determine the corrective action needed to prevent further damage or future failure.


Having issues with your Allison transmission not going into gear can be a worrying experience, especially if it’s something you’re not familiar with. There are several possible causes of this issue, and each one will require a different approach to fix it. In this article, we’ll cover the different potential causes of an Allison transmission not going into gear, as well as what you can do to troubleshoot and repair the problem.

Common Causes

One of the more common causes for an Allison transmission not going into gear is a faulty solenoid. The solenoid is responsible for controlling the flow of fluid in and out of the transmission, so if it’s not working properly, it can cause shifting issues. Another potential cause is a worn shift cable or linkage, which can cause the transmission to not engage properly. It’s also possible that there could be an issue with the pressure control solenoid or governor pressure sensor, both of which can affect how the transmission shifts.

Diagnosing The Problem

In order to diagnose which of these potential problems is causing your Allison transmission to not go into gear, you’ll need to take your vehicle in for an inspection by a qualified technician or mechanic. They will be able to use specialized diagnostic tools to identify any faults that may be present in your vehicle’s drivetrain system.

Once they have identified any potential issues with your vehicle’s drivetrain system, they will be able to provide advice on what needs to be done in order to rectify the problem and get your car shifting properly again.

Repairing The Problem

If it turns out that you do need to replace parts on your car in order to get it shifting properly again, then this may involve replacing the faulty solenoid or shift cable/linkage. It may also involve replacing other components such as the pressure control solenoid or governor pressure sensor if these are found to be defective.

In some cases, it may even be necessary for you to have your entire drivetrain system replaced in order for your car to shift correctly again. This can be quite costly but may be necessary depending on how much damage has been done by the faulty components or drivetrain system.


Once all repairs have been made and your car is shifting correctly again, it’s important that you stick with regular maintenance schedules in order to ensure that any further issues don’t arise down the line. This involves changing fluids regularly and having regular inspections done on all components related to the drivetrain system such as filters, gaskets and seals etc., as well as checking all cables/linkages for signs of wear/damage over time.

By doing this regularly you will help keep any future problems at bay and ensure that your car is running optimally at all times.


If you are having trouble getting your Allison transmission to go into gear, there are a few things you can check before taking it to a mechanic. First, make sure all the fluid levels are correct and that the fluid is in good condition. If the fluid is dirty or low, it could be causing the problem. Also, check the shift linkage to make sure it’s properly adjusted and lubricated. If everything looks normal and you’re still having trouble shifting, then it may be time to take it to a professional for further diagnostics.

Check Fluid Levels and Condition

The first thing you should do when trying to diagnose an Allison transmission that won’t go into gear is check all of the fluid levels and condition. Make sure the transmission oil level is correct, as well as the coolant level and brake fluid reservoir level. Its also important to make sure that all of these fluids are in good condition – if theyre dirty or low, this could be causing your transmission problems.

Check Shift Linkage

The next step is to check all of the shift linkage and make sure its properly adjusted and lubricated. This includes checking all of the bellcranks, shift rods and other components in order to ensure they are functioning properly. If any of these components are out of alignment or not adequately lubricated, this could be preventing your transmission from going into gear properly.

Have Professional Diagnose Problem

If you have checked all of these items but your Allison transmission still won’t go into gear, then it’s time to have a professional diagnose the problem for you. A qualified technician will use specialized diagnostic equipment to pinpoint exactly what is causing your transmission issues so that they can get it fixed quickly and correctly.

FAQ & Answers

Q: What is the most common cause of an Allison transmission not going into gear?
A: The most common cause of an Allison transmission not going into gear is a faulty shift solenoid or a problem with the transmission control module (TCM). Other possible causes include low transmission fluid level, worn clutch plates, dirty transmission filter, and faulty shift linkage.

Q: How do I check the fluid level in my Allison transmission?
A: You can check the fluid level in your Allison transmission by locating the dipstick located on the side or bottom of the transmission and removing it. Wipe off the dipstick and reinsert it fully into the tube. Pull it back out and look at the markings to see if you need to add more fluid.

Q: What should I do if my Allison transmission will not shift into gear?
A: If your Allison transmission will not shift into gear, you should first check to make sure that there is enough fluid in the system. If there is enough fluid, then you should check for any mechanical issues such as worn out clutch plates or a broken shift linkage. If none of these are present, then there may be an issue with either a faulty shift solenoid or a problem with the TCM.

Q: How can I tell if my Allison transmission has a bad solenoid?
A: You can usually tell if your Allison has a bad solenoid by checking for codes on your vehicle’s diagnostic scanner. Additionally, you may also experience symptoms such as shifting delays, unexpected shifts, and harsh shifts when trying to change gears.

Q: What should I do if my Allison Transmission still won’t go into gear after checking all these things?
A: If your Allison Transmission still won’t go into gear after checking all of these things then it may be time to take it to a professional mechanic for further diagnosis. They will be able to pinpoint any problems with your vehicle’s system and recommend repairs that are necessary for getting your car running smoothly again.

In conclusion, if your Allison Transmission is not going into gear, the most likely cause is a faulty shift solenoid. Other possible causes could include a malfunctioning transmission control module, electrical issues, or low fluid levels. It is important to inspect the transmission and its components before attempting any repairs. If you are unable to diagnose and repair the problem yourself, it is recommended that you take it to a certified technician for service and repairs.

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