How to Tell if Your Diesel Truck Needs a New Transmission

Diesel trucks are becoming increasingly popular on the roadways. In 2020, new car sales saw a 14% decline in sales. However, diesel truck and SUV sales increased a whopping 28%

Your diesel truck takes care of so much. They’re reliable, heavy-duty, high-mileage, transport vehicles used for both personal and commercial needs. But as much as these trucks take care of our jobs and families, take some time to care for them as well. 

Being extra cautious with precious cargo like your diesel truck is never a bad thing. If the transmission blows, and you need a new transmission, the truck won’t work. This won’t be a problem that allows you to drive on through it.

It’ll simply cease to work.

The average cost of installing new transmissions on a diesel truck ranges from $2,500 to upwards of $8,000. Don’t allow a serious transmission issue to sneak up on you and your budget. Look for these telling signs that your truck might need a new transmission so you’re prepared for what comes your way.

Pay Attention to the Gears

You don’t have to be an expert mechanic or a technician to pick up on signs that a transmission is showing signs of trouble. Transmissions don’t usually blow up out of the blue. They generally give warning signs that they need repairs.

If the gears on your diesel truck have been sticking or slipping while driving, this means you’re suffering from irregular gear shifting. Irregular gear shifting is a sure sign the transmission is having issues.

If the gearbox refuses to shift or is becoming increasingly more difficult to switch from one gear to another, the gears are sticking. Gear slipping can occur alongside this or by itself. This is when the gearbox suddenly shifts from 3rd gear into 4th possibly, or even neutral, which can be dangerous.

The noises and physicality coming from the gears are also indicators of a transmission’s overall health. The gearbox of manual diesel trucks will audibly grind when you’re shifting from one gear to another.

In an automatic, the sign isn’t auditory, but it’s felt. Automatic diesel trucks will shake when moving up or down in gears when the transmission is faulty.

A faulty gearbox not only makes your vehicle unreliable and potentially dangerous, but it can also be a clear sign that your diesel truck needs a new transmission.

Struggle for Power

For a diesel truck to accelerate smoothly, the transmission must be strong. If the truck is taking longer than usual to accelerate or the acceleration is rough and delayed, that shows the transmission is not working as intended.

If this is accompanied by whining sounds or knocking noise, it’s time to get it checked out. Even if it may not be the transmission, proper maintenance and awareness of your truck’s health is crucial for a longer-lasting vehicle overall.

Listen to the Noises

Diesel trucks are generally louder naturally than other trucks out on the roads. The average decibel levels for diesel trucks is 100 dB while gas-powered passenger cars emit 65dB. 

This can make hearing irregular noises more difficult. The best way to check for noises, if one isn’t screaming at you while driving, is to place the truck in neutral. Once it’s in neutral, leave it running for a little to hear if it’s noisier than usual.

Noisier than usual means any buzzing, clunky, or whining sound coming from the truck might be your transmission speaking to you, asking for help.

What Do You See?

Take some time to closely look for specific things that can be indicators of your transmission’s health. The transmission fluid is a great place to start.

Generally, healthy transmissions will have a bright red fluid color. Throughout using the truck, this may fade to a deep or light pink, which is normal.

Health transmission fluid is fairly easy to see through and does not have a burnt smell. If you look at the transmission fluid in your diesel truck and it’s murky with a dark red to brown color and smells burnt, your transmission needs to be checked.

Checking transmission fluid health is quick and easy to do so while changing the oil on your diesel truck.

The familiar panic that sets in when you see the check engine light come on, or worse yet, start flashing, isn’t necessarily only tied to the engine. The sensor for this light is sensitive enough to pick up abnormal vibrations and problems before they’re noticeable. Even if no codes are picked up from it, it may be worth asking an experienced technician to look at the transmission.


When after accelerating or parking, pay attention to how the truck smells. If there’s a distinct burning smell coming from the truck, it could be that transmission fluid is burning.

If the gears are grinding or causing the truck to shake, the friction motion they engage in could cause a burning smell as well.

Thinking About a New Transmission?

If any of these signs seem familiar because you’re experiencing them regularly, it’s time to give your diesel truck some TLC and get it checked out.

Anticipating a costly expense, like potentially replacing old transmissions with a new transmission in your diesel truck, is crucial for budget planning and maintaining stress levels lower.

Contact us and make an appointment to ensure that the transmission of your diesel truck is cared for by trusted professionals.

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