GM Truck 6 Speeds

Let’s talk about GM truck 6 speeds. 6L80’s, 6L90’s

I’m going to touch base on the most common problem that I see with this transmission. It is a worn pressure regulator valve. This valves in the pump and the transmission needs to be removed for access.

The role of the pressure regulator valve is to regulate the hydraulic pressure overall inside of the transmission. There are many more valves that take this pressure and move it to certain areas. When the main valve fails or starts to fail, there becomes a lack of pressure that should be there. This will cause all sorts of problems. One of the most common problems is a torque converter clutch shudder. It feels like a washboard road while you’re driving down a dirt road. This can be very subtle at first, but gets to be quite violent as time goes on.

Catching this early can definitely determine the cost of the repair. If let go too long, there is a lot of internal damage that is expected to happen. One of the main items is the torque converter. Clutch fails due to lack of pressure applying the clutch. The pressure regulator valve is a main component of this process.

Also, the programming of the transmission computer has a factor in how long that clutch will last in a vehicle. To gain better fuel economy, the manufacturer will apply this clutch, sometimes as low as second gear. That can be a problem. More on that later.



The valve shown here is only slightly worn. The issue with this transmission was caught very early.