Most full-size trucks and SUVs with a 6L80, 6L90 use a JMBX full-size (300mm) style converter. It’s a single-disc, non-captive clutch unit that is somewhat similar to late 300mm 4L60-E converters. When cutting the JMBX open, converter rebuilders report that a high percentage of units show extreme damage due to the clutch piston and front. GM's new Hydra-Matic 6L80 & 6L90 transmissions are the first of a new family of modular six-speed rear-drive transmissions. The transmissions feature two overdrive gears and a wide, 6.04:1 gear ratio spread to improve performance and fuel economy when compared with conventional four- and five-speed automatic transmissions.
The 6L80 Hydra-Matic transmission is a 6 speed automatic transmission manufactured by General Motors. It was created to help GM meet ever more demanding CAFE regulations on their vehicles. By utilizing more gearing, the 6L80 keeps the car in it’s power band longer, improving the MPG of the vehicle between 4-7% (over the previous generation fours speed transmissions) depending on the configuration of the vehicle that it’s in.
It began replacing the 4L60E transmission in many vehicles starting in the 2006 model year. The 6L80E went mostly into large vehicles with V8 motors. For the most part, this transmission has been phased out by the 8L90E already, but is still in prodution.
Unlike the 4L60E and 4L80E, the 6L80 is not always referred to as with the E on the end because it’s been over 25 years since the last non electronic GM transmission has been in production.
The 6L80 was used in trucks, particularly in the GMT 900 platform. The exceptions to this would be the 2006-2014 Corvette, 2006 G8, 2010-2015 Camaro, and the Chevrolet SS. In fact, the only 2017 model year vehicle that still comes with this transmission is the Chevrolet SS.
The 6L80 is a robust transmission and can handle a ton of power. In fact the input torque rating is 440 lb. and it can handle a total gross vehicle weight of 8,600 lb, which makes it a great transmission for LS swaps with no modification needed whatsoever.
It’s a longitudinal transmission (that’s what the L in 6L80E stands for). This means that it’s designed for rear wheel drive vehicles only. It has a line pressure tap for diagnostic purposes.
Here are the basic specs for the 6L80E:
|Manufacturer: General Motors|
|Type: 6 Speed Automatic, 10-12.6 quart capacity (dependent upon application)|
|Max RPM: 6500|
|Input Shaft: Application dependent|
|Torque Converter Lock: Yes|
|Overdrive: Yes, 2 gears|
|Case Length: 23.5″|
|Outer Case Material: Cast Aluminum|
|Controlled by Computer: Yes|
|Dry Weight: 195 lb.|
Wet Weight: 207-227 lb. wet
6L80E Gear Ratios
The 6L80E uses four under drive gears and two overdrive gears. It does not have a direct 1:1 ratio like the 4L80E and 4L60E, which is worth noting. The 6L80E’s gear rations are as follows:
There are two super easy ways to tell whether or not the transmission is a 6L80E. Which one you use is going to depend on whether or not the transmission is in or out of the vehicle. If the transmission is in the vehicle you can use the RPO tag in the glove compartment. If you know the RPO code for the transmission you are golden. It’s like where’s Waldo. Just keep scanning it until you find the one you are looking for.
GM Transmission RPO Codes:
- 6L80– MYC
- 6L90- MYD
- 4L60E- M30
- 4L60E- M30
- 4L60E- M30
- 4L65E- M32
- 4L80E- MTI
Every modern GM vehicle has one of these sheets in its glove compartment. Use it to verify the vehicle has a M30 4L60ENow, if the transmission is out of the vehicle (or if you don’t trust a sticker), the 6L80E has an 18 bolt case. That’s more than almost any other GM automatic transmission. It looks nearly identical to the 6L90. For all practical purposes, these two transmissions are completely interchangeable.
The 6L90 has a beefier set of gears and many internal upgrades. Like most GM automatic transmissions, the easiest way to tell them apart is by using the pan gasket. Conveniently, the main transmission that the 6L80E is going to be confused for all have a different number of pan gasket bolts. See the pictures below to help you tell if you have the right transmission.
They all look really similar, so make sure that you bother to count the pan gasket bolts, especially if you have an untrained eye.
That’s pretty much all that’s to it. If you have any questions that I may be able to help you with, drop a comment or contact me.