Upgrading the 6L80 Transmission in 2015 Silverado 1500 Trucks

Overview of the 2015 Silverado 1500 6 Speed Transmission

The 2015 Chevrolet Silverado 1500 pickup truck comes equipped with a Hydra-Matic 6L80 six-speed automatic transmission. This transmission was introduced by General Motors in late 2006 and is found in many of their truck and SUV models.

Specs of the 6L80 Transmission

The 6L80 transmission is a heavy-duty six-speed automatic designed for longitudinal engine configurations. Key specifications include:

• Six forward gears with gear ratios ranging from 4.03 to 0.67
• Maximum engine torque rating of 664 lb-ft
• Maximum Gross Vehicle Weight Rating (GVWR) of 18,000 lbs

The 6L80 is a computer controlled transmission using electronic sensors and actuators to control shifting. It features clutch-to-clutch shifting for smooth and efficient performance.

Benefits of the 6-Speed

There are several advantages to having six forward gears compared to four or five speed transmissions:

• Better acceleration - Closer gear ratio spacing improves performance
• Increased fuel economy - An extra overdrive gear reduces rpm at highway speeds
• Grade climbing ability - Optimized gear ratios provide more torque when needed
• Towing performance - Improved gearing gives more control with heavy loads

Upgrading the 6L80 Transmission

The 6L80 transmission is built for toughness right from the factory. But for truck owners wanting smoother shifts, better durability, and increased torque capacity, there are a number of upgrades available.

Shift Kits

Shift kits involve replacing the transmission's valves, springs, and clutch plates to optimize the hydraulic pressure. Benefits include:

• Faster, more positive shifts
• Lower operating temperatures
• Increased clamping force and torque capacity

Upgraded shift kits tailored for the 6L80 are offered by companies like TransGo and other brands popular with transmission builders.

High Performance Valve Bodies

Replacing the OEM valve body with an improved aftermarket valve body is another transmission upgrade option. It allows for:

• Smoother, consistent shift feel  
• Proper line pressure needed for performance builds
• The ability to handle increased torque loads

Brands like Sonnax make specialized high performance valve bodies for GM 6-speed transmissions.

Improved Clutches

Upgrading the automatic transmission clutches is crucial for handling additional torque loads from performance engine builds. Benefits of upgraded clutches include:

• Increase torque capacity and clamping force
• Improved durability
• Longer service life

Many companies offer tough steel 6L80 performance clutches to upgrade from OEM.

Common Failure Points

Even with all the upgrades available, there are a few well-known problems on some model years of the 6L80 transmission that owners should look out for.

Harsh 3-4 Shift

Some Silverado 1500 models exhibit a very firm 3-4 upshift, especially when the truck is cold. Most times this is remedied by servicing the transmission and installing an updated TCM calibration.

TCM Connector Issues

On early model 6L80 transmissions, electrical issues at the transmission control module (TCM) connector can appear. This may require inspecting terminals inside the plug for contamination or damage. Replacing the connector or wiring harness may be necessary.

Premature Pump Failure

In some cases, the oil pump has been known to fail prematurely on this transmission. Debris ingestion from a previous failure can cause pump damage. Inspecting the pump screen and replacing it if plugged can help avoid issues.

Installing a 6L80 transmission with all the latest engineering updates and experienced machine work is recommended to avoid any major problems down the road.

Finding a 6L80 Transmission Builder

For Silverado 1500 owners wanting to build an upgraded 6L80 transmission tailored for their truck, finding a quality transmission shop is key. Ideal builders will have 6L80 expertise, OEM engineering knowledge, and the latest blueprinting and machining capabilities to produce a reliable, high-torque transmission. Brands that builders trust for the 6L80 include Alto, Sonnax, TransGo, TCS, and others.

Researching 6L80 transmission builder reviews and reputation can help find the right shop for your needs. Building rapport by talking directly with builders that demonstrate knowledge on optimizing your transmission is also advised.

Investing in a professionally built transmission brings peace of mind knowing you have a personalized gearbox designed for your exact vehicle and performance goals.

FAQs

What are some common problems with the 6L80 transmission?

Some common 6L80 transmission problems include harsh 3-4 shifts, TCM connector issues causing electrical faults, and premature oil pump failures in some cases.

How much horsepower can the stock 6L80 handle?

The stock 6L80 transmission can reliably handle around 550 horsepower. Upgraded builds with improved internals can handle over 800 horsepower.

What causes harsh upshifts in the 6L80?

Harsh upshifts are most often caused by worn transmission fluid, faulty solenoids sticking, or clutch packs that are worn out. A 6L80 rebuild with updated parts is often needed.

Should I upgrade the torque converter when rebuilding?

Yes, installing an upgraded billet torque converter matched to your performance specs helps transfer more power and torque while also aiding transmission durability.