I traveled about 30 miles out of town yesterday to take my kids sledding, and when we got there it smelled like something was burning(not oil) then we tried to put the truck in 4wd and it seized for a minute and made a loud clunking noise. When we finished sledding we started the truck again and drove we were able to go back to into 2wd but it started to make this whining noise. We stopped at the nearest auto shop and the guy said we needed another transfer casing but seemed like he was unsure on what was causing the noise!!! Please help if you can my husband needs to check the transfer casing but does not know how to remove it please if anyone knows help me please this is our only vehicle and we are far from rich!!!
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I have a 1999 GMC Sierra 4wd how do you remove the transfer case?
- Thread starter brinabee
- Start date
Too much information required to give a quick answer here.
First off, this is some major maintenance to remove a transfer case. So I hope he is at least moderately mechanically inclined. If he starts this project and half way into it he discovers this is beyond his capabilities he could end up having to tow a basket case to a mechanic. A professional mechanic will usually charge extra to repair a basket case.
He needs a repair manual before he starts a project like this. See the link below.
Also, the Auto Zone website has an excellent Do It Yourself section. You must register, but I never received any SPAM by registering here. Here you will get free access to an online service manual. You can not download the manual. However you can print any pages that you need.
I have some other suggestions if your husband wants to attempt this project.
With any major maintenance the first step is to disconnect the battery. If your radio has a security code set make certain you know the code before you start. Better yet reset the code to all zeros before you start. This disables the security on the radio. This way you will not have problems getting the radio to work after the maintenance is complete.
Most people have access to a digital camera. Before he starts crawl under the truck and take some pictures of the transfer case area from several different angles. This could be used later to jog his memory if he forgets how something goes back together.
Get some 1 quart and 1 gallon zip lock bags, generic will do. Get a couple of sharpies. Get a roll of 2 inch masking tape.
Each time he removes a component put all of the fasteners, brackets, and loose parts in a zip lock bag and label it with a sharpie. If the part is small enough bag the part also. If the part is too big to be bagged keep the small parts bag with the part. This keep things more organized. It will be less likely he will lose parts or have parts left over when the project is finished.
Each time an electrical connection is disconnected or a line is disconnected label it with some masking tape and a sharpie. This will be helpful when putting things back together.
A transfer case will be heavy. Usually you would use a transmission jack to raise and lower the transfer case. It also helps to hold the transfer case on place then it is unbolted from the transmission or to hold it in place while bolting it back into position. Check with your local tool rental store.
Sucks to have something like this happen over the holidays. Good luck with your project.
First off, this is some major maintenance to remove a transfer case. So I hope he is at least moderately mechanically inclined. If he starts this project and half way into it he discovers this is beyond his capabilities he could end up having to tow a basket case to a mechanic. A professional mechanic will usually charge extra to repair a basket case.
He needs a repair manual before he starts a project like this. See the link below.
Also, the Auto Zone website has an excellent Do It Yourself section. You must register, but I never received any SPAM by registering here. Here you will get free access to an online service manual. You can not download the manual. However you can print any pages that you need.
I have some other suggestions if your husband wants to attempt this project.
With any major maintenance the first step is to disconnect the battery. If your radio has a security code set make certain you know the code before you start. Better yet reset the code to all zeros before you start. This disables the security on the radio. This way you will not have problems getting the radio to work after the maintenance is complete.
Most people have access to a digital camera. Before he starts crawl under the truck and take some pictures of the transfer case area from several different angles. This could be used later to jog his memory if he forgets how something goes back together.
Get some 1 quart and 1 gallon zip lock bags, generic will do. Get a couple of sharpies. Get a roll of 2 inch masking tape.
Each time he removes a component put all of the fasteners, brackets, and loose parts in a zip lock bag and label it with a sharpie. If the part is small enough bag the part also. If the part is too big to be bagged keep the small parts bag with the part. This keep things more organized. It will be less likely he will lose parts or have parts left over when the project is finished.
Each time an electrical connection is disconnected or a line is disconnected label it with some masking tape and a sharpie. This will be helpful when putting things back together.
A transfer case will be heavy. Usually you would use a transmission jack to raise and lower the transfer case. It also helps to hold the transfer case on place then it is unbolted from the transmission or to hold it in place while bolting it back into position. Check with your local tool rental store.
Sucks to have something like this happen over the holidays. Good luck with your project.
crawl under the truck you will see the t-case there is a bolt pattern facing the front of the truck should be 15mm and they will be in a circle pattern between the trans & t-case that is were you remove it. you will have to take things off as needed ot remove the t-cast.
Molson02536
New member
New Process Model 246 Part -Time Transfer Case Electric Shift, 1999-On GM 1/2 & 3/4 Ton Trucks, Suburban, Tahoe & Yukon. Recommended fluid for NP246 part number 12378508 Autotrack lI 2 Quarts. The NP246 has a design problem, the pump can wear out the case causing premature failure and leaking. Magnesium cases are soft; aluminum pumps are harder. But before we think it's the transfer case we need to look at the big picture. On the full size, the front actuator is electric, not vacuum.
When in 4wd mode, a switch on top of the transfer case conducts 12 volts out to the actuator. Wire #50 (brown) is the 12v feed, and it conducts to the light blue wire (#900) to the actuator.
When shifted out of 4wd, the switch opens up and no voltage goes to the actuator.
Check voltage at the connector for the front actuator (at the front differential - it looks like a large bullet that threads into the front diff.) If it has 12 volts, the actuator is the problem. If it does not have 12 volts, check the transfer case switch and the power feed to the transfer case.
I'll assume it is the actuator, if the plug to the actuator is getting 12 volts when in 4wd.
The way this actuator works, is it is a sealed chamber that gets heated by voltage. When it heats, the pin in the end swells and pushes a shift fork in the front differential. The shift fork engages a spline on the passenger side of the differential, and boom! you have 4WD.
GM offered an upgrade to this actuator that is a motor instead of a heated device. However, it requires a small harness addition, a spacer, and a new actuator. It is about a $150 to $200 option.
If I were you, I would buy a new heated actuator. They are available at most auto parts stores, and are about $90. They are also on eBay for about $55 plus shipping. These are very easy to change - just thread out the old one, and thread in a new one.
Good luck, That actuator is usually the problem 90% of time. But also check the fluid level in the transfer case and front differential which would help indicate where the problem is.
When in 4wd mode, a switch on top of the transfer case conducts 12 volts out to the actuator. Wire #50 (brown) is the 12v feed, and it conducts to the light blue wire (#900) to the actuator.
When shifted out of 4wd, the switch opens up and no voltage goes to the actuator.
Check voltage at the connector for the front actuator (at the front differential - it looks like a large bullet that threads into the front diff.) If it has 12 volts, the actuator is the problem. If it does not have 12 volts, check the transfer case switch and the power feed to the transfer case.
I'll assume it is the actuator, if the plug to the actuator is getting 12 volts when in 4wd.
The way this actuator works, is it is a sealed chamber that gets heated by voltage. When it heats, the pin in the end swells and pushes a shift fork in the front differential. The shift fork engages a spline on the passenger side of the differential, and boom! you have 4WD.
GM offered an upgrade to this actuator that is a motor instead of a heated device. However, it requires a small harness addition, a spacer, and a new actuator. It is about a $150 to $200 option.
If I were you, I would buy a new heated actuator. They are available at most auto parts stores, and are about $90. They are also on eBay for about $55 plus shipping. These are very easy to change - just thread out the old one, and thread in a new one.
Good luck, That actuator is usually the problem 90% of time. But also check the fluid level in the transfer case and front differential which would help indicate where the problem is.