6l80 vs 6l90: Difference Between 6l80 and 6l90 Transmissions

6l80 vs 6l90

When it comes to automatic transmissions, the 6L80 and 6L90 are similar transmissions  found in GM vehicles Both transmissions are members of General Motors’ 6L series of transmissions, known for their durability and efficiency.  While there are a lot of similarities between the two, we’re going to compare them and help you better understand the differences between the 6l80 and 6l90 transmissions.

Key Differences Between 6l80 and 6l90 Transmissions

Size & Weight

One of the key differences between the 6l80 and 6l90 transmissions is their size and weight. While nearly identical, the 6l80 is a slightly smaller transmission, with a total weight of around 195 pounds dry and 23.4″ in length. In comparison, the 6l90 transmission is about 1.5″ longer

6l80 and 6l90 Transmission Fluid Type and Capacity

Both the 6L80 and 6l90 transmissions requires around 13.5 quarts of transmission empty. When it comes to transmission fluid, both the 6l80 and 6l90 transmissions use Dexron IV  transmission fluid that is designed to provide optimal performance and protection for the transmission.

  • Backward compatible with previous Dexron automatic transmission fluids and can be used as a much-improved replacement for older vehicles/transmissions originally using previous Dexron fluids
  • Improved performance over previous Dexron fluids in: friction durability, viscosity stability, aeration and foam control, and oxidation resistance
  • Potential to enable improved fuel economy and longer transmission life
  • Provides for extended drain intervals. Provides consistent shift performance, even in extreme conditions.

What Vehicles Are They Best Used In

One of the key differences between the 6l80 and 6l90 transmissions is the type of vehicle they are intended for. The 6l80 transmission is commonly found in medium-duty vehicles such as half ton and smaller trucks, vans, SUVs, and cars where its size and weight are better suited to the vehicle’s capabilities.

The 6L90 transmission is found in heavy-duty vehicles such trucks and vans used for towing and hauling.

Which Transmission is More Durable?

In terms of performance and durability, both the 6l80 and 6l90 transmissions are capable of being reliable and long-lasting depending the situation. However, the 6l90 is the stronger of the two transmissions.

The 6l90 has about a 220 ft lbs output torque rating over the 6l80 with a 885 ft lbs rating.  The strength increase of the 6l90 is largely in part due to the change from a smaller diameter 32 spline output shaft to a larger diameter 29 spline shaft.

Fuel Economy

The fuel economy differences between the 6l80 and 6l90 are minimal at best and are dependent on the vehicle that each is is.  Girven the fact that the 6l90 is in heavy duty vehicles that weight more, you would expect these vehicles to get worse fuel milage compared to a 1500 truck with a 6l80 due to their weight.

Towing Performance

Both the 6l80 and 6l90 are capable of towing within their weight range, but between the two, the 6l90 is a much better option.

The 4l60e is at a real disadvantage when towing anything more than a car on a trailer.  Since the 4l60e is somewhat inconsistent on its own, towing with it isn’t the best, especially as it ages.

The 4L60e has four forward gears and a single reverse gear, while the 6L80 has six forward gears and a single reverse gear. This allows the 6L80 to use more gears to improve the towing experience which  may provide more precise control over the engine’s speed and torque output, potentially allowing for smoother, more efficient acceleration and deceleration when towing heavy loads.

Third, the 6L80 is equipped with a more advanced, electronically-controlled hydraulic system that allows for faster, more precise shifting and improved fuel efficiency. This means that the 6L80 can potentially provide better performance when towing heavy loads, especially when operating at higher speeds or in challenging driving conditions.


Ultimately, the answer to the question “which transmission is better, the  6l80 or 6L90” is it depend on the specific needs and requirements of the vehicle and the driver While the two are designed to be used in very similar cars and trucks, and many feel that the 6l80 is a better transmission for your every day vehicle. However, when it comes to towing or heavy hauling, the 6l90 is the better option given its output torque rating and overall strength increase over the 6l80