Yoram Levy from Israel gave us a call with a 2022 Chevrolet Traverse using a 9T65 that suddenly lost reverse. He had found a check ball missing in his valve body which he points out in figure 1 (above).
Figure 2, below, shows how bad the plate was where this ball passed through. GM usually provides the function of check balls in their Technician Guides; but with the 9T series transmissions, we could not find that information. What we could find, however, is the holes in the spacer plate with circuit number identified that correspond with their hydraulic circuits as seen in figure 3.
So, it took going to the hydraulics and trace the circuit to determine the function of this missing ball. In doing so, it was discovered that this was the number 9 check ball. This ball blocks 5-7-R (24) from entering the Drive 2 Circuit (18) in Reverse. In forward it blocks Drive 2 from entering the Rev/57R circuit which is the reverse feed circuit from the manual valve. With this ball missing, not only where there be a no reverse complaint, both fifth and seventh gear will be compromised as well. (See Figure 4).
Interestingly enough, we received another call from Chuck at Wholesale & Auto Repair having an intermittent no-reverse complaint with a 2020 Chevy Malibu using the 9T transmission. It too had an issue with the same ball. At the time, a spacer plate wasn’t available, so he deburred the plate and put in a slightly larger ball to remedy the problem. As the saying goes, “Necessity is the mother of invention.”
Since these two occasions we have received several others with the same issue, so this is a common problem you will very possibly encounter if you haven’t already. A new spacer plate is now available from GM using part number 24293403 (figure 5). Of course, you will need to find your own ball!