Case Study: General Motors Automobile Wave Plate Failure

2009 Chevrolet Traverse – 6T70 / 6T75

Our customer found information about the inherent failure of the wave plate in a particular clutch drum in his transmission. A problem we are well aware of. The failure of this particular wave plate results in the total failure of the transmission. However, in this instance our customer wanted to see if he could have the wave plate replaced before it broke, saving him thousands of dollars down the road, as well as a tow bill. We were more than happy to go along with his train of thought. We are always interested in legitimate methods to saving our customers money.

More Background on the Issue:

As a result of the myriad of premature transmission failures, GM with much pressure decided to extend the warranty on this particular transmission to 10 years and 120,000 miles. However, most fail just outside of that. The design of this particular transmission was a joint effort between Ford and General Motors. However, we don’t see the wave plate issue with Fords version of this transmission. 

What is a Wave Plate:

A wave plate is a mostly flat disc that is used in the stack up in a clutch drum. It’s a cushion (spring) for the transition when the clutch drum is applied/engaged. It is 1-2 mm in thickness a probably costs all of about $0.50 to manufacturer. However, when the wave plate fails, it becomes like throwing a handful of change down a garbage disposal. Hopefully that paints the picture in leading to the total failure of the transmission and your vehicle no longer moving.

Wave plates are used in almost all clutch drums in automatic transmission design. 

In this particular transmission, known as the Hydra-Matic 6T70 and/or 6T75 the particular drum is the 4,5,6 drum. It specifically affects 3rd, 5th and reverse. 

Pre-Emptive Repair:

Our customer’s line of thinking was right on the money. He had no symptoms or evidence of a problem, but, replace it before it breaks and save thousands of dollars. It’s not a matter of if, but a matter of when it will happen. With the exception of this wave plate, we found this model of transmission to be very solid and worthy of a preemptive repair. GM and Ford did a great job. However, the machining of the particular part, the wave plate, must have somehow been substandard or the control of the transmission could have somehow been different from the cousin transmission in the Ford version (6F55). 

This transmission is not only used in this Chevy Traverse, it’s also used in

  • 2007-2009 Buick Enclave
  • 2008-2009 Chevrolet Equinox, Malibu
  • 2009 Chevrolet Traverse
  • 2007-2009 GMC Acadia
  • 2007-2009 Pontiac G6
  • 2008-2009 Pontiac Torrent
  • 2007-2009 Saturn AURA, OUTLOOK
  • 2008-2009 Saturn VUE

Equipped with FWD or AWD and 6-Spd Automatic Transmission, (RPO MH2, MH4, MH6, or MY9)

How We Handle it at Tri-City Transmission

No two set of circumstance are the same. We always start with a good diagnosis in order to verify the overall health of the transmission. If the transmission checks out healthy, sometimes we are able to access and service this wave plate without removal of the transmission. However, this is not practical or recommended in all situations depending on age, mileage, transmission performance and accessibility to the transmission in the car. This transmission is used in many different vehicles with different option packages, certainly effecting access in vehicle.

In situations where we have to remove the transmission as a whole, we are then able to verify the health of the rest of the transmission. We can replace the wave plate, address any other worn components in the transmission and provide a warranty for the transmission as a whole. This is the most ideal and still saves a ton of money.

Also Partial Failures

In this case, the vehicle has become symptomatic in 3rd gear, 5th gear or Reverse but the vehicle still drives fairly normal. In this case, that handful of loose change has not quite made it to the blades in the garbage disposal. This certainly needs transmission removal, but will still save money if they don’t wait. We can fix it before your vehicle quits moving and it gets real expensive.