Identifying GM 6T70 Series TEHCM Generations Using VIN & RPO Codes

There is a 2012 Buick Regal in the shop with a strange no-shift condition and pressure switch codes. Suddenly you realize to question whether the correct TEHCM is installed. That is our subject. We will discuss how to identify the GM 6T70, 6T75, 6T80 generations by using the Regular Production Option (RPO) code and the VIN.

Knowing the unit generation is important for programming and TEHCM usage, not to mention geartrain parts in various units also differ generation to generation. Figuring out what unit variant you have and therefore what TEHCM should be installed ONLY going by the serial ID (i.e. OE part number) of the TEHCM you pull out of the tranny is not always a good idea. I have seen more than a few cases of a wrong TEHCM installed in vehicles by that method — one after another, usually! That is called the Follower Syndrome: “Someone else installed the wrong TEHCM, so we will, too!”

What happens if the wrong TEHCM is installed in a vehicle? Well, that can vary wildly. It may program like nothing is wrong. But afterwards, you may think you are venturing down the rabbit hole, as some call it. Think how frustrating it would be to discover your problems weren't caused by a bad TEHCM, but because someone ELSE put the wrong module in your customer's vehicle. This applies whether you're installing a new OE TEHCM or Sonnax Gen. 2 remanufactured module GM6T70-G2-TEHCM. Even if you've done your due diligence to match the OE part number on the old TEHCM to the ones listed for the replacement, a module designed for Gen. 2 6T70, 6T75, 6T80 units won't work properly in a Gen. 1 series build. Not a fun experience!

The VIN & RPO Process

Regardless of this RPO article, let’s clarify the fact that you can’t go wrong ordering OE parts by VIN only… unless parts are packaged wrong, and that does happen occasionally!

The RPO codes can be found on a placard labeled “Service Parts Identification” in the glove box. If not, look in the trunk or the door jamb! Transmission RPO codes all start with the letter M, but not all M codes are transmission RPO codes. One odd occurrence I experienced: the RPO code “MNK” is the same for both a 5-speed Allison and a GM Gen. 3 6T40. So, RPO codes require attention to the details!
See features below:

• RPO codes are not necessarily distinct per generation or year model.
• There may be more than a singular RPO code per transmission generation and year model.
• RPO codes may be repeated occasionally.
• A different year/model vehicle with the same transmission and the same RPO code may use a different TEHCM part number as indicated in the table below.

Let's get started!

1. First secure the VIN from vehicle and RPO code for transmission. If for any reason you can’t find the RPO code, then use the VIN only to look up the code. There are a few ways to do this:

a. Go to ACDelco TDS website shown in Figure 1 and to this link www.acdelcotds.com/rpolookup and input VIN, it will produce RPO codes for that vehicle VIN. If you do not have an account with ACDelco, you must create an account first.

Figure 1 – Input VIN to Find RPO

b. Secondary method: If you have Snap-on^® Shop Key/Mitchell 1^® ProDemand, then input per VIN and ID vehicle. The application will show RPO data under the “Service tab/General Information/RPO codes/Introduction/RPO CODE DESCRIPTION”. You may view more than one transmission RPO code, and the reason is that vehicle may have several engine options along with different transmission options. When that occurs, match the engine and year range to the transmission RPO code.

c. Another option is to input VIN on a website such as RepairLink^® to view VIN attributes, and it will generally have exact RPO codes for the transmission shown per the VIN. RepairLink and most web sources will require you to create an account first.

2. Once you secure the transmission RPO code, match the code to the available selections shown in Figure 2.

Figure 2 – Identify Appropriate 6T70 TEHCM Using RPO Code

Hopefully now you can see that RPO codes can be a great inclusive tool: when combined with year/model data, they allow you to narrow down information and select the proper TEHCM for a vehicle. Have a great time with RPO codes and keep in mind these same techniques work for other GM transmissions and parts.

Jim Mobley is a Sonnax technical communication specialist. He is a member of the Sonnax TASC Force (Technical Automotive Specialties Committee), a group of recognized industry technical specialists, transmission rebuilders and Sonnax Transmission Company technicians.