The GMC Sierra is a full-size pickup truck from GM (General Motors) and it’s one of the most popular vehicles in its segment. It’s one of the bestselling vehicles in the USA because of its power.
However, like all vehicles on the road today, there are a few common issues that crop up, especially if you plan to keep your vehicle for the long haul.
As any mechanic will tell you, GMCs are some of the most reliable vehicles on the road, but that doesn’t mean they don’t have their own set of problems. Issues with the transfer case are one of the common problems with GMC Sierra.
The transfer case is a complex piece of machinery that can cause headaches for even the most experienced mechanics. That’s why you should familiarize yourself with this guide for GMC Sierra transfer case problems and how to fix them.
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What is the GMC Sierra Transfer Case?
The transfer case is one of the most complicated parts of a modern truck. Also known as a transfer gearbox, a transfer case is a part of a four-wheel drive or all-wheel drive (4WD/AWD) vehicle that switches between two-wheel drive and four-wheel drive.
This component has a bit of a strange name since it doesn’t transfer anything. Instead, it splits the power between the front and rear wheels.
It’s a dual-drive system that helps the vehicle’s front and rear axles to transfer power to the wheels. If the transfer case breaks, it can cause the front and rear wheels to have different speeds. You will usually notice a grinding or a clicking sound from the drivetrain when the transfer case is broken.
In some vehicles, the transfer case is integrated into a gearbox. Transfer cases are used in both on-road and off-road vehicles such as pickup trucks, sports utility vehicles (SUVs), off-road vehicles, full-size vans, and heavy equipment.
The transfer case on your GMC Sierra has two main jobs. It helps your truck climb steep inclines, and it allows you to shift between two- and four-wheel drive. If your GMC Sierra is having trouble climbing hills or shifting gears, it might be time to install a new transfer case.
GMC Sierra Transfer Case Problems and Solutions!
Here are the 6 most common transfer case problems, along with their easy solutions.
1: Transfer Case Leaking Seals
If the transfer case begins to leak, the fluid reservoir of the case will begin to empty, and eventually, your vehicle will stop functioning. If you’re having transmission fluid leaking from your GMC Sierra transfer case, you probably don’t want to wait around for it to destroy your transmission.
A faulty transfer case seal can cause a lot of damage if it isn’t taken care of immediately. The good news is that you don’t need to replace the entire transfer case just because of a faulty seal.
Finding the source of the leak is essential to fix the leak properly. The best way to find the source of the leak is to remove the transfer case and put it in a bath of ATF (Automatic Transmission Fluid) and distilled water to check for any leaks.
The GMC Sierra transfer case leaking seal problem may be caused by the following conditions.
- Worn or damaged rubber seals that allow the lubricant to escape.
- A damaged or worn seal inside the transfer case or transfer case motor.
- An improperly installed seal.
- A defect in the transfer case or encoder motor.
Solution
If your transfer case is leaking, you’ll need a new transfer case seal. You can replace the seal on your own with a few simple tools. If the leak is around the front pump, you might be able to fix it by tightening the bolts on the pump.
2: Transfer Case Noisy Gears
The transfer case has gears that can make some grinding noise. The noise is usually the result of the gears grinding when you move the shifter from park to drive or reverse.
The most common reasons for a transfer case to make noises are a worn front/rear pump shaft bearing, worn or damaged front pump gears, or worn out or damaged rear pump gears.
Solution
First, check to make sure that your oil is full and changed regularly, as this will be key to ensuring quiet operation for many miles to come. If your gears are old and worn out, you’ll need to replace them with new ones for smooth running.
3: Loose Bolts
Loose bolts are a major problem in the transfer case of a GMC Sierra. If these bolts are loose and don’t go back into place, the entire transfer case can come out of the back of the truck and onto the road.
A loose bolt, or a missing bolt, in the GMC Sierra Transfer Case, can cause a warning light on the dashboard, and in some cases, it can also lead to a failure of the transmission to shift gears.
Solution
Looking at the underside of the transfer case is the best way to determine if this problem exists. Gently pull out the rear end of the transfer case to inspect for loose bolts.
If there are any loose and worn-out bolts, replace them with new ones. If they’re in good condition and just loose, then tightening them will do the job. In order to work around loose bolts in the transfer case, you’ll need to use the proper torque wrench.
Since loose bolts are usually caused by corrosion, the best thing you can do to avoid loose bolts is to keep your GMC Sierra transfer case clean and dry.
4: Fluid Problems
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The fluid in the transfer case acts as a lubricant for the gears, bearings, and seals. If the fluid in the transfer case is low, then the gears won’t be lubricated and will wear out prematurely. Additionally, If the fluid is too thick, it can lead to the transmission not being able to shift gears smoothly.
The PCM (Powertrain Control Module) monitors the fluid level of the transfer case through the speed sensor. If the PCM senses there is not enough fluid, it’ll set a code and illuminate the Check Engine Light.
Solution
It’s important to make sure that you check your transfer case fluid level regularly. If it’s low, fill it up and add fluid until it reaches the ‘Full’ mark on the dipstick.
You’ll need to replace the transfer case fluid with the new one if it’s dirty or muddy. Most auto manufacturers and professional mechanics suggest that you should replace your transfer case fluid every 50,000 miles.
However, the frequency of fluid change will depend on how you use your GMC Sierra. If you use your vehicle to tow large loads regularly, you’ll need to replace the transfer case fluid more often. You can consult the user manual of your truck to find out how often you should change transfer case fluid.
5: Problem Staying in 4WD Mode
If you are having trouble keeping your truck in 4WD mode, you are most likely experiencing a transfer case failure problem. When the transfer case is in good operating order, it’ll automatically transition between 2WD and 4WD modes as needed.
If it is not operating properly, you’ll notice that your car frequently shifts between the two driving modes, and it won’t be able to stay in 4WD mode at all. This can be a dangerous safety hazard since it might lead you to lose control of the truck while driving.
Solution
The best way to solve this problem is to take your vehicle to a professional mechanic and get it checked as soon as possible.
6: Clogged Lines in Transfer Case
A clogged transfer case can cause a variety of different issues. For example, if your transfer case is clogged, you may not be able to shift into a four-wheel drive. Additionally, you might also notice that your truck doesn’t have enough power when you try to accelerate.
When you’re dealing with a clogged line, it’s important to take action right away. If you don’t, you’ll have some serious problems down the road.
The most common cause of transfer case failure in GMC Sierra is the use of motor oil that does not meet the requirements of the transfer case.
Check with your local auto parts store to ensure the oil you are using is labeled for use in your transfer case. You can also check the owner’s manual for additional information.
FAQs About GMC Sierra Transfer Case Problems
Q: How Do You Replace a Transfer Case?
Replacing the transfer case can be quite a daunting task. Therefore, it’s recommended that you take your vehicle to your local mechanic for repair or a dealership for replacement. You can also DIY if you have the right tools, patience, and basic know-how on transfer case replacement.
Q: How Much Does It Cost to Replace the Transfer Case?
The cost of transfer case replacement will vary depending on the parts that need replacing. If you’re planning to get it replaced by a mechanic, it’s best to call local mechanics and get quotes. If you notice there are problems after the vehicle has been in an accident, it’s recommended that you take it to a mechanic or dealership for diagnosis.
Q: How Long Does It Take to Replace GMC Sierra Transfer Case?
The Chevy Silverado transfer case replacement can take between 1-5 hours depending on your experience with the mechanic and the model of your pickup. The majority of repair shops should be able to replace it for you within a couple of hours.
Q: How Do I Know If a Transfer Case Replacement Is Needed?
You should be able to figure out whether you need to replace the transfer case based on the symptoms you are experiencing. For example, if the engine is not getting enough power, or your vehicle is having trouble shifting gears, then you might need to replace the transfer case.
Final Thoughts
The GMC Sierra is a popular and powerful truck, but it has some issues with the transfer case even after years of improvement.
The transfer case does not require much maintenance. However, when there is a problem with the transfer case, you will need to fix it right away. The problem could be severe and could cause a lot of damage to the car.
If you know what to look for, you can fix many transfer case problems on your own and save yourself some money in the long run.
However, you should keep in mind that the transfer case is a complicated part of the GMC Sierra’s transmission system, and it can malfunction if not handled correctly.
Like many automotive systems, the transfer case consists of several parts that can break or fail over time. You can repair a faulty transfer case yourself with a few tools and some basic knowledge of car repair.
But if you’re not sure what’s wrong with your transfer case, it’s best to go to a mechanic or dealership that has the right equipment to diagnose the problem.
We hope you found this article helpful and informative. We wish you the best of luck in solving your transfer case problems in your GMC Sierra.
My name is Tom Harris, founder of this blog. I’m a mechanical engineer with 20 years of experience in the automotive industry. I’m here to help you with your vehicle’s problems, easy fixes and share my insights and experience so that you can enjoy your rides more.