6L80 vs. 6L90; What’s the difference?

The 6L80 and 6L90 transmissions are both great gearboxes. This article will break down the differences between the two. Let’s start with the 6L80, the transmission on which the 6L90 transmission is based.

Understanding the 6L80 transmission

First brought to market in the mid-2000s, the 6L80 transmission is a 6-speed auto transmission made by GM at their main transmission engineering center in Michigan, and at their other transmission center in Ohio. The 6L80 transmissions are built for RWD as well as AWD/4WD applications. These transmissions offer clutch-to-clutch operation in addition to a wide-range gear ratio for great performance and efficiency.

What vehicles will you find using a 6L80 transmission gearbox?

You’ll see the 6L80 mostly in GM vehicles such as Cadillac’s Escalade, Chevrolet’s Silverado 1500, Camaro, Suburban, Tahoe, GMC’s Sierra 1500, and Yukon.

Is the 6L80 transmission effective?

Like most things in life, you get out of the 6L80 what you put into it. If you maintain it well, consistently replace fluids, and keep it tuned up, the transmission will run well for a very long time.

What are the main differences between 6L80 and 6L90 transmissions?

While they are very similar systems, the 6L90 transmission can be considered a higher-demand and heavier-duty version of the 6L80 6-speed auto. What makes it heavier duty is its fortified input gear set that comes with two additional pinion gears compared to the 6L80 (for a total of six), as well as a fortified output gear set that uses significantly wider gears compared with the 6L80. The 6L90 has gear flexibility that goes directly to the clutches; in addition, the 6L90 has an extra clutch plate in each clutch compared with the 6L80 for help with higher-demand usage. You can find a 6L90 version without this extra clutch plate if you want to more closely match the 6L80 for certain transmission situations, however.

All in all, the 6L90 shares about three-quarters of the same parts the 6L80 has, with the main difference being that the 6L90 case sits about 35 mm longer compared with the 6L80 case. The 6L90’s case also gives space for additional fastening between the transmission and transfer case for when you might want improved drive noise and vibration control.

To sum this up a bit more concretely, the biggest difference between the 6L80 and 6L90 transmissions is how fortified the internal components are, with the 6L90 being built to handle more stress overall for heavier-duty loads. The 6L90 transmission case is longer by about 1-3/8”, which is designed to create extra space to house the two extra pinion gears (for a total of 6). The 6L90 also has fortified input/output gear sets, and the heavy-duty uses for the 6L90 receive an additional clutch plate in each pack. When it comes to price differences between the 6L80 and 6L90 transmissions, they can vary but normally remain within a few hundred bucks as you can see here, https://reman-transmission.com/transmission-codes/?code=6L80, and here, https://reman-transmission.com/transmission-codes/?code=6L90, through their 6L80 and 6L90 price comparisons.

Is there any extra output for the 6L90 as a result of these upgrades?

These combined upgrades boost the 6L90 maximum output torque to 885 lb-ft, with a GCVW increase up to over 21,000 lbs.

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