6 Common GM 6.6 Gas Problems | Expert Solution

As you know gas engines are better at accelerating than diesel engines. GM 6.6L gas engine is not an exception. Though some users find many issues with this engine.

Poor transmission speed, and knocking noise are most commonly found issues with GM6.6L gas engines. They can be fixed if you react as soon as the problem arises. A quick reaction can help you not to lose too much money fixing it. 

So here in this article, We will be covering the fixing of GM 6.6 gas problems, the cost of fixing, common problems with it, etc. You will get a clear idea about the GM6.6L gas engine’s repair cost and at last, some FAQs will be answered.

6 Most Common GM 6.6 Gas Problems and Solutions

General Motors unleashed two cars with GM6.6L gas engines in 2020. Few problems are randomly found in the new model by the users.

1. Poor transmission speed

To have the best performance from the six-speed option you need an appropriate transmission.GM6.6L gas engine reported a lack of proper transmission.

So many people contend that the ten-speed transmission will outrun the 6.6/6-speed combination. Moreover, many people believe that the ten-speed is very much occupied with its upshifts and downshifts. This can draw some new set of problems.

What happens?

The poor transmission speed can cause several problems such as misfiring, acceleration problems, and poor performance. Ultimately the reliability of the engine reduces.

How to fix Poor transmission speed?

The reason behind this problem can be a dead battery, filter problem, or lack of transmission fluid in the engine. So make sure all of them are perfect. If not, changing them will fix your problem.

But most commonly users found GM6.6L gas engine design is the problem itself.

 2. Knocking Noise

It is the most frequently found GM 6.6L gas problem. It is a very simple problem. But the challenge is to find where the sound is coming from.

Knocking noise is only heard when the engine is stopped. And you can’t hear them while the engine is new. After a few months of use when you change the engine oil for the first time this problem arrives.

What happens?

A knock kind of sound always comes out from the engine. It can cause a rough run of the engine.

Many users reported they first met this issue after approximately 6600 miles of driving when they changed their engine oil for the second time.

How to fix Knocking Noise?

Specialists suggest an upgrade in engine oil will solve this problem. But it is not always the case as many GM6.6L gas engine users reviewed oil changes that didn’t solve their problems.

The root behind the issue needs to be found. To do that check your engine parts carefully. It can be the transmission case or valve springs that are causing the knocking noise.

3. Anonymous tick sound

Sometimes the engine’s parts are not properly lubricated as a result a random sound like tick tick is heard. You can’t hear it when the car is stopped.

The engine is made with many rotating parts. As the engine drives, a little problem can cause big ones because the parts are interconnected.

What happens?

You can hear the sound nonstop as if something is not right. Not solving the issue as soon as possible can cause a direct engine failure or higher use of gas.

How to fix the Anonymous tick sound?

You need to find where the sound is coming from and your instinct should tell you that. After finding out, you will find ways to stop it like changing some wire or springs.

4. Lifter issues

Lifters are significant parts of a gas-powered motor since they aid the kickoff of interior valves. 

What happens?

A flawed motor lifter could keep one of the valves from working properly. It can make the engine run rough. The PCM looks for motor-related issues that could cause an expansion in vehicle discharges, for example, a misfire caused by breaking down a lifter.

How to fix Lifter issues?

If you are facing this problem there’s not much hope of repairing it. Replacing the valve lifter is the only solution.

5. Engine using high gas

The GM6.6L gas engine has a 10. 8:1 compression ratio thanks to direct injection, which is a class-restrictive trademark. There’s likewise another dynamic oil pump to assist with temperature guidelines.

But after all the improvements are done, high gas usage is still reported by the customers. Sometimes this engine uses too much gas to operate.

What happens? 

Performance of the engine reduces, acceleration problems, rough engine running can be found due to this problem.

How to fix the Engine using high gas?

The fuel pump should be checked properly. If there is any broken part it should be replaced. Sometimes cleaning the filter can also improve the result.

6. Lower torque

The diesel engine of Duramax has greater power and authority than the 6.6L gas engine. It is a very big problem with this engine.

If you see the facts you will find that the GM 6.6L gas has less hp and comparatively lower torque. But most of the customers are happy with its acceleration.

What happens?

Lower torque is a drawback for GM 6.6L gas engines. It can be affected by skillful driving but most commonly it’s the problem with upshifting and downshifting. 

How to fix Lower torque?

The design is a big factor in this problem. So you cannot do anything about this problem. It is doing what they made it do.

What Are The Signs of GM 6.6L Gas Problems?

An engine doesn’t fall apart in a day. Before going to a full breakdown it always gives us some indication. So if you have a GM 6.6L gas engine that has some issues you will notice the following things:

  • Acceleration Issues 
  • Weird sounds from the engine 
  • Reduction of transmission speed 
  • Noisy valves 
  • Engine stalling and other issues 
  • Misfiring the engine
  • Poor performance
  • Injector failure
  • The abs and StabiliTrak light come on

If you face any of these issues it’s better to check your engine properly and fix the problems as soon as possible.

How Much Does It Cost To Fix GM 6.6L Problems?

It is not possible to say a specific amount that will fix your GM 6.6L. The cost management can be done in two steps.

Mechanic cost

It is the charge a servicing center charges for their service but not the parts. There is a wide range of servicing centers with different service charges.

The charge depends on the model of your engine you want to be serviced. You are Normally $400-2000 for servicing this GM6.6L gas engine.

Parts cost

The cost totally depends on what items should be repaired and how bad their condition is.

In the beginning, problems are not that serious and most of the time they can be fixed by cleaning the engine. Sometimes a wire change or addition of some tiny parts can make a big difference. That will not be that costly.

But a big problem can cost you more than $1000 like full replacement of different parts. Here is a thing that must be mentioned: ‘Gas engines are comparatively cheaper to fix than diesel engines.’


We have discussed GM 6.6L gas engine capability, problems, solutions, and some other aspects. We will be answering some of the FAQs about the 6.6L gas engines. Find out if they can help you.

What is the MPG on a 6.6L GM?

The EPA doesn’t have any more test engines that are attached to heavy vehicles. Local reports say the GM 6.6L gas engine managed to score 19 MPG on the highway.

Is the Chevy 6.6 a good engine?

The GM6.6L V-8 gas motor with direct infusion, appraised at 401 hp and torque 464 lb-ft.In comparison to the previous gas motor, this represents an increase of around 11 percent in horsepower and a 22 percent increase in maximum force. So yes, the Chevy 6.6 is a good engine.

How much oil does a 6.6 gas engine take?

The engine can take approximately 8 quarts(7.5liters) with the filter. But without the filter, it can take approximately 10 quarts(9.5liters).


After the latest modification has been done most of the GM 6.6L gas problems are sorted out and the overall performance improved. The customers are mostly satisfied but critics say several things. 

Whatever, you know the problems of the GM 6.6L gas engines and what critics say about them. If the problem is not solved you must go to a mechanic and look for solutions to protect your engine from further damage.

Related Posts:

Similar Posts