Introduced in late 2005 to become the 6-speed replacement for the 4-speed transmissions such as the 4L60E, the 6L presented several new challenges. The early release of this product line was introduced in Cadillacs and Corvettes, but before long it became mainstream for GM’s light duty pickup and SUV lines.
What does this mean to all of us in the industry? Well, if your focus is domestic torque converters, you’ve probably touched a lot of these by now, and because of that, you’ve faced several challenges along the way. This converter was first presented at the seminar in 2014 and followed up in 2015; so why write another article about it now?
We’re all aware that it’s common for converters to evolve. As a converter’s lifecycle continues, we often find ourselves having to do more during the rebuild process to get it back to an acceptable level of quality. In addition, the manufacturer will often make running changes to their product to solve quality issues they’ve identified, or to adapt it to a new application.
In this article, we’ll review some of the issues we’ve seen and identify a few changes we’ve noticed.
One common early failure with this converter was loss of friction material. This was often related to rivet failure, but not always. If not a broken rivet (figure 1), then maybe a leaking rivet (figure 2), that contributed to a shudder.
Because of these issues, it appears there has been a change to the rivet. Figure 3 shows the early rivet that fails. Although there doesn’t appear to be a lot of difference in the two; you can tell the difference when you have them side by side or by measuring the thickness. The early rivet head is 0.040” (1.016 mm) thick (figure 3), while the later rivet head (figure 4) is about 0.065” (1.651 mm) thick.
Another common early failure with this converter was a cracked damper cage (figure 5). Is this a design flaw or a failure that results from a harsh shudder?
I don’t know the answer to that, but regardless, it’s broke, and we’ve all seen the results when that occurs. The piston and cover become collateral damage associated with all these failures.
The good news is there’s a replacement cover available, a piston is on the horizon, we’ve seen fewer broken cages than in the past, and word on the street is there are solutions for this problem being worked on.
Now that we’ve identified the common failures you need to address with this converter, there’s one more twist: The converter changed around 2014. It still uses the JMBX alpha code (of course there are several numeric codes), and it still fits the common GM models.
The differences start with the impeller. When looking at the internal fin angle, you’ll notice the late model design now has a kickback to a more neutral position instead of the early, low-stall angle.
The stator has changed from 18 blades to 14 blades, and the piston damper now has four single springs and two doubles instead of the six single springs that were common in its early years.
Needless to say, this converter has created many challenges or opportunities, depending how you look at things. Either way, keep your chin up and remember: If you’re tired of these, there are 8-, 9-, and 10-speed opportunities right around the corner.