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Transmission Digest

Serving the aftermarket since 1981, Transmission Digest is dedicated to the powertrain industry.

07/24/2025

Thinking like a transmission means understanding what information the transmission has, how it interprets that information and how it uses the information to select the correct forward gearing. You also have to understand how the transmission prioritizes performance when it is compromised.

Let’s go over three rules for transmission diagnosis.

Even with codes and datastream information, you must be able to think like the transmission to find the correct transmission diagnosis.

07/22/2025

In today’s digital age, your shop’s reputation is no longer just based on the quality of the repairs or the friendly in-person interactions between service advisors and customers. Increasingly, customers turn to the internet to research and decide where to take their vehicles for service. The power of online reviews and word-of-mouth marketing has grown to unprecedented levels, and ignoring these factors can significantly hinder your shop’s ability to grow and thrive.

The power of online reviews and word-of-mouth marketing has grown to unprecedented levels, and ignoring these factors can hinder your shop.

07/18/2025

The seven-speed DCT is like having two manual transmissions shifting together with two clutches. While one clutch and sub-transmission is engaged to the wheels, the other sub-transmission is selected and waiting to be shifted. The DCT is shifted with electric motors that move the shift forks. One actuator controls the odd gears, while the other actuator controls the even gears and reverse. Another set of actuators engage and release the dual clutches.

Read our story on servicing this DCT here:

When there are issues with the actuators in the Hyundai/Kia Dual Clutch Transmission, the DCT will slip and have harsh shifts.

07/16/2025

Building a legacy takes more than just skill. It takes dedication, resilience and a willingness to carve your own path.

Chris Harmon, owner of Harmon Performance Transmission in New Richmond, Wisconsin, is a third-generation transmission builder, following in the footsteps of his father and grandfather. From tearing down transmissions at just five years old to forging ahead to create his own company, the trade is in his blood. Even so, stepping out on his own to start his shop wasn’t easy.

With industry challenges, rising costs and the pressure to provide a quality build, Harmon had to prove that he could not only continue the tradition but take it to the next level. Read his story here:

Chris Harmon, owner of Harmon Performance Transmission in New Richmond, Wisc., is following in the footsteps of his father and grandfather.

07/14/2025

On this episode of The Builder’s Bench, we’re discussing the P0871 fault code: overdrive pressure switch. Specifically, we’re talking about why this code pops up on the Chrysler 68RFE transmission, model years and 2019 and newer.

Watch the video for more:

On this episode of The Builder's Bench, we're discussing the P0871 fault code: overdrive pressure switch. Specifically, we're talking about why this code pop...

07/11/2025

On this episode of Powertrain Perspective, our guest is Jim Dial, who manages the transmission mechanical line for. Sonnax Sonnax. Jim has been a frequent contributor to TD as part of our TASC Force Tips series we provide in partnership with Sonnax. The most recent article in that series was on the recent GM 10-speed recall, and Jim goes into a bit more detail on that in this interview.

Watch our conversation with Jim here:

Jim Dial of Sonnax details the recently announced GM 10-speed recall: How the issue starts, what causes it, and what shops should know.

07/09/2025

In March, GM issued a Safety Recall for the GM 10L1000 and Gen. 2 10L60, 10L80 and 10L90 transmissions. The recall states that vehicles with the listed 10-speed transmissions may experience a “Momentary Wheel Lock-up” condition at higher speeds that could also include a downshift back to second gear. It also states that a control valve in the valve body can be susceptible to excess wear over time, resulting in a gradual loss of control pressure.

Here's what you need to know about this recall:

In March, GM issued Safety Recall N242480630 for the GM 10L1000 and Gen. 2 10L60, 10L80 and 10L90 transmissions.

07/07/2025

Third-generation transmission builder Chris Harmon is making a name for himself in the performance sector. In this story, read what makes him a Vehicle Care RockStar.

Chris Harmon, a third-generation transmission builder, is making a name for himself in the performance sector.

07/02/2025

This article addresses an intermittent issue encountered with a 2016 Ford Explorer Police Interceptor with a 6F35 transmission, which was reported by a local first responder. The vehicle was towed in after the customer indicated that the wrench light had illuminated, and that the vehicle had a no-move condition. Upon initial inspection, I was surprised to find that there were no diagnostic trouble codes, and when I placed the vehicle in gear, it moved without issue.

For the rest of the story, read our article here:

The customer took back his vehicle but returned one month later, saying that the no-move condition had recurred while at the station.

06/30/2025

DTC P2714 is still somewhat of an elusive code. Why? We are all too familiar with performance codes indicating a mechanical failure of a solenoid, or a compromised valve or valve bore in the valve body, or an internal transmission problem causing a clutch to not engage properly—in this case, the K2 clutch.

But before Dominick went down the wrong diagnostic path due to this unit having a solenoid performance code, he made a very important observation.

Read that observation, and what followed, in our story here:

A generation two Volkswagen 09G transmission recently came into AC Transmissions with DTC P2714 stored in the system.

06/27/2025

The interactive and easy-to-use digital edition of Transmission Digest’s June issue is ready for viewing now. Read it here:

Transmission Digest - Transmission Digest June 2025

06/25/2025

In the past 20 years, 4MATIC has become an option on every vehicle Mercedes-Benz sells. The current generation of the Mercedes-Benz 4MATIC system is mechanically bulletproof. But what can go wrong are the electronics that manage the system, and the seals that keep the fluids inside the transfer case and differentials.

Read the full story here:

What can go wrong on the Mercedes-Benz 4MATIC system are the electronics, and the seals in the transfer case and differentials.

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