Other Articles - July - 2020

6L80/90E Park Rod: “A Closer Look”

Have you ever had part that you’re not sure about, and wonder if you should use it? It looked good, but there was just something about it! At some point in time, we have all encountered situations where a part was in question. It looks good enough to use, but you didn’t feel right about it, so you ask a coworker to take a closer look at it. Let’s take a closer look at the 6L80/90E Park Rod!

GM updated the original Park Rod in 2008 to a heavy-duty Park Rod. The failure was the rivet, or end of the Park Rod, would wear out. The vehicle would lose park and/ or have a noise in reverse while backing up. Even the updated heavy-duty rod and rivet end still wore out. It was not until 2018 when the manufacturer got the hardness correct at the end of the Park Rod.

According to industry sources, the hardness was off by only 2 numbers on the Rockwell Harness scale. The Rockwell scale is a hardness scale based on the indentation hardness of a material. The Rockwell test measures the depth of penetration of an indenter under a large load (major load) compared to the penetration made by a preload (minor load).There are different scales, denoted by a single letter, that use different loads or indenters. The result is a dimensionless number noted as HRA, HRB, HRC, etc., where the last letter is the respective Rockwell scale. When testing metals, indentation hardness correlates linearly with tensile strength.

That might not seem like a big deal, but when it comes to safety, it does. Unless you are the Incredible Hulk, you are not going to stop a vehicle when park suddenly stops holding. Let’s take a closer look at the wear you’ll see on the rivet end of the Park Rod, and what is not usable and what is useable.

The rivet end wears from the spring pushing the actuator or the actuator slamming against it numerous times whenever park is engaged or released.When you’re inspecting the Park Rod assembly, use the reference chart to identify any failures or damaged parts (Figure 1). IMPORTANT: Every Park Rod on the 6L80-90E units MUST be inspected.

When the rivet end wears out, the Park Rod bullet and spring separate from the rod due to wear at the rivet end (Figure 2). You might see that the spring is extended and not preloaded (Figure 3).

Park is the most important part of any rebuild. It’s critical that it works and holds every time. If it doesn’t, the vehicle can cause severe damage, not just to property, but to lives.

The Inspection can be done with the Park Rod still installed in the transmission, but it’s easier if you remove it. To inspect the Park Rod in the transmission, the internal components should be removed. Move the rooster comb to the manual low position, and then pull the Park Rod towards the Park Pawl. You can now move the Park Pawl out of the way (Figures 4 and 5).

Now compare your Park Rod to the chart in Figure 1 to see if your Park Rod is good or needs replacing. Many technicians replace the Park Rod on every 6L80/90E unit they rebuild.

The Park Rod can be replaced without removing the actuator guide, to remove the guide, all internal components must be removed. With the parts removed from the case, you can better inspect the rivet end, and replace the two O-rings on the actuator guide.

Every technician that removes these parts has their own method to get the roll pin out of the case. Use the GM puller (Figure 8), or tack weld a nut to the roll pin and use a slide hammer. Some technicians simply use a pair of side cutters and work it out. Welding a nut to the pin using a slide hammer seems to be the easiest method.

Part Numbers for the updated heavy-duty rod are:

• 6L80-E: AC Delco 24280048 12.5 inches long

• 6L90-E AC Delco 24280048 14 inches long

Special thanks to Steven Spence, Newnan, GA., for the photographs used in this article.