Silverado & Sierra Transmission Cooler Line Replacement & Repair - Transmission Cooler Guide (2024)

If you’re a Chevy Silverado or GMC Sierra owner, then you know that your truck is a workhorse. But even the toughest trucks need routine maintenance to stay in good condition.

One often overlooked item that many Silverado owners end up needing to change are the transmission cooler lines. This is a common item that that takes a great deal of abuse in areas where rust is common.

The transmission cooler lines play an important role in keeping your transmission running smoothly. They help to cool the transmission fluid, which prevents overheating and damage to the transmission.

When they’re clogged or leaking, it can cause all sorts of problems with your truck.

If you’re noticing problems with your transmission, such as slipping gears, delayed acceleration, or a burning smell, it might be time to change your Silverado’s transmission cooler lines. The good news is that this is a relatively easy job that most people can do themselves.

Here are the steps you need to take to change your Silverado’s transmission cooler lines:

1. Jack up the truck and place it on jack stands.

2. Remove the skid plate and the splash guard.

3. Disconnect the transmission cooler lines from the transmission.

4. Remove the old lines and replace them with new ones.

5. Reconnect the transmission cooler lines and reattach the skid plate and splash guard.

It’s important to note that there are a few different ways to do this job, so be sure to follow the instructions that came with your new lines. Also, be careful not to damage any of the other components in the area when you’re working on the transmission cooler lines.

If you’re not comfortable doing this job yourself, then you can always take your truck to a mechanic. But it’s a good idea to know how to change your Silverado’s transmission cooler lines, just in case you ever need to do it yourself.

Silverado & Sierra Transmission Cooler Line Issues

As we went over in our guide to transmission coolers for Silverado or Sierras, you should check your transmission lines if installing an aftermarket transmission cooler or if your truck is older and in an area where rust is problematic.

If you’re installing a transmission cooler you will need to work with your factory transmission cooler lines, so now would be the time to see if your Sierra or Silverado’s transmission lines are leaking or they will need to be replaced.

It is common that you will find your transmission lines are leaking due to rusting out over time, especially if you live in an area that is more prone to causing your truck to rust. The most common area for this is typically the section of line that runs on the passenger side by the engine as shown below.

How To Remove & Replace Transmission Cooler Lines on Silverado or Sierra.

Replacing the trans cooler lines on your truck is not to hard of a task. The hardest part will be removing the lines from the transmission. These fittings are typically held in by clips that go into fittings, which can make things easier or harder depending on how you choose to remove the lines.

Typically it is easier to remove the clips that hold the metal lines in place rather than messing around with a wrench in a tight space.

How To Remove Transmission Lines From Radiator on Silverado or Sierra

Removing the transmission lines from the radiator on your Silverado or Sierra is pretty straight forward and easy. Just like the lines going from the transmission, the lines at the radiator are held in by C clips into fittings that route fluid to the cooler inside the radiator. The image below shows what the fittings look like on your truck’s radiator.

To remove these lines first peel back the small plastic cover on the fitting and simply use a pick or small screw driver to pop the clips out. It is always best to have a couple of extra C clips around when removing old ones due to the fact they tend to pop off with force and fly elsewhere.

Silverado & Sierra Transmission Cooler Line Diagram & Routing

The design of the transmission cooler lines on most GM trucks is fairly straight forward. If your truck has setup without a transmission cooler from the factory, you’ll only have 2 transmission cooler lines going to and from the transmission to radiator, the send and return. If your truck does have a factory cooler, then the return line at the top of the radiator will then go to the front of the truck to the cooler, rather than straight back to the transmission.

This often confused people who aren’t familiar with transmission cooler line orientation, and they confuse the send and return lines.

Below is a basic Silverado and Sierra transmission cooler line diagram showing the standard hot (send) and cool (return) lines as the flow through a factory cooler setup.

So whether you have a 4.8, 5.3, or 6.0 LS powered truck , an older 5.7 small block, or a more modern truck with an LT motor, the transmission cooler flow is very similar.

Note: Newer trucks with the 6l80 transmission have their cooler lines coming from the driver side of the transmission, but the same idea applies.

1999 – 2006 Silverado & Sierra Transmission Cooler Line Replacement

The 1999 – 2006 “NBS” Silverado and Sierra is extremely common, and so are their old, rusty transmission cooler lines. The video below shows you how to remove and replace transmission cooler lines on your 99-06 Silverado or Sierra easily in your own driveway or garage.

1999 – 2006 Transmission Cooler Lines

The following transmission cooler line part numbers work on Chevy Silverado and GMC Sierra applications for model years:

1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2006.5

Dorman part numbers:

• 624-117
• 624-124
• 624-153

2007-2013 Silverado & Sierra Transmission Cooler Line Replacement

The 2007 – 2013 “NNBS” Silverado and Sierra is another extremely common version of the truck, and while there may be a high percentage of NBS trucks with transmission coolers that need replacing, the NNBS style trucks are not as bad due to their age. The video below shows you how to remove and replace transmission cooler lines on your 07 – 13 Silverado or Sierra easily in your own driveway or garage.

2007 – 2013 Silverado & SIerra Transmission Cooler Lines

The following transmission cooler line part numbers work on Chevy Silverado and GMC Sierra applications for model years:

2007, 2008, 2009, 2010, 2011, 2012, and 2013

Dorman part numbers:

• 624-117
• 624-124
• 624-153