What's Up with My Scanner? Why You May Have Issues Clearing Some DTC's
As most are aware, a transmission is not just a transmission anymore, in fact it has not been a stand-alone component for several decades now. A lot of the discussions I get involved in these days have to do with issues outside of the transmission which manifest themselves as transmission problems. This may be electrical issues, drivability related issues or even issues such as DTC’s setting in ...

Slowing Down: Diagnosing a Grade Braking Issue
Grade braking was introduced in the 2006 Allison applications. It’s a feature that many customers have learned to value, especially for those that use their vehicles to tow or carry heavy loads. There are two types of grade braking used today: normal grade braking and cruise control grade braking (which was introduced in 2009). And like regular grade braking, it’s transparent to the custome...

An Introduction to the 2020 10-Speed Allison
The name “Allison” immediately conjures up a picture in the mind of the consumer of transmissions that exemplify quality, durability, and longevity. Allison, as most of you are aware, was a division of General Motors for decades. Even after being split off from GM, the GM/Allison relationship continues to this day. The Allison applications are thought of as units used in medium and heavy-du...

Looking for a Needle in a Haystack - P0747 on 9T Applications
So much of what you work on today is challenging, to say the least. Many shops lament, regarding the days when life and the transmission business were much simpler, customers were much easier to please and transmissions were much less of a challenge to repair. Sad to say, I do not think that the turbo 350 or the C6 are going to make a triumphant return any time soon. So, what is in the mix for ...

Looking for Gremlins in a 9 Speed: When is a Transmission Problem NOT a Transmission Problem?
Those of you who attend seminars and classes that I have taught through the years have heard me “preach” about how important it is to look for issues outside the transmission before you start looking for what’s wrong inside the transmission. More times than I can count, the problem or the cause of that tough problem that a shop is trying to diagnose ends up being something outside the transm...

No PUN Intended: Changes to Valve Body Calibration on Some GM Transmission Applications
One thing about this industry is that change is a constant thing. In the ATRA seminars over the last few years, we have included detailed information regarding the processes that need to be followed when servicing the GM 8, 9 and 10 speed applications. As we have seen, some technicians that have not attended the seminars have struggled to get the units to shift correctly. The 8, 9 and 10 speed ...

It Looks Good!! Operation, Inspection, Diagnosis of System/Circuit Grounds
Decades ago, when I started in this profession, electricity was one of those areas that most shops, technicians and even engineers, avoided when at all possible. Today’s vehicles are changing at a rate never before seen in the history of the automotive industry. With the advent of more speeds, more electronics, as well as most manufactures announcing that they have or will shortly unveil fully e...

Where Did Those Extra Numbers Come From? A Look at 7 Digit DTC Diagnosis
For more than 50 years, the EPA (Environmental Protection Agency) has been in charge of making sure the vehicles you repair meet all the federal emissions and fuel economy standards set forth by the federal government. The liaison between the EPA, the US department of Transportation (DOT) and the automotive/ truck manufacturers is an engineering organization known as SAE (Society of Automotive Eng...

What is Causing that? A Look at the GM 8L90's Most Common Concerns
Introduced in 2015, with a major update in 2018/19, the 8L90 is starting to appear in shops around the country. Used in numerous GM car and light truck applications, the 8L90 transmission and its little brother the 8L45 are a challenge even for the most experienced dealership or repair shops. The 8L90 can be identified by the following RPO codes, M5Q, M5X and new for 2019, MQE while the 8L45 is...

Heavy Duty Shifts: Another Look at the Duonic 6 Speed DCT
Things that seemed impossible just a few short years ago are now common place in our industry. Eight, nine, and ten speed units as well as Hybrid and Dual Clutch applications are entering the market at a rapid rate. In a joint venture between Mercedes and Mitsubishi, the Fuso brand was born. Fuso is sold worldwide and has quickly become one of the leaders in the class 3, 4 and 5 small/medium duty ...

Sipping Fuel
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A Look at the New Dynamic Fuel Management System and How it Affects Your Transmission Product changes; some technicians love them, some technicians hate them, but we all have to deal with them. As I’ve preached for decades, a transmission isn’t just a transmission, it’s part of a complete vehicle propulsion system. Today we’re seeing more and more operational characteristics from differen...

Tackling Clutch Failure in the GM 6L80/90
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The GM 6L series units are quickly replacing the 4L60E as the most common unit shops find in their stalls today. Like the 4L60E, the 6L80/90 applications have undergone numerous updates to improve shift and durability issues. A lot of updates have occurred to the parts to address the problems you may be experiencing. Like the 4L60E, trends have developed that make diagnosis and repair easier as...

Just Lock Me Up, A Look at E LOC: A Different Type of Lockup System
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I’m often asked, “When are the constant changes in vehicle technology going to slow down?” The answer is quite simple: They won’t! 10 years from now, you’ll look back at today’s technology and think, “Wow! That stuff was simple when compared to what we’re working on today.” Technology has permeated every part of today’s vehicles. It’s easy to wonder, “What was wrong with...

Moving Right Along: A Look At The Latest CVT, The VT40/CVT-250
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Like many of you, I’m far from a fan of most CVTs. I guess I’m just set in my ways but I often wonder if people really test drive CVT-equipped vehicles prior to purchasing them. But, like other things in life, the CVT is evolving. The progression over the last couple of years from some of the manufacturers has been impressive, to say the least. Subaru and now GM have developed units that tr...

Make It Stop Shaking! Isolating Vibration Issues
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Vibrations can be one of the most frustrating things that you can have to repair. Finding the source of the vibration and then eliminating the cause can be a challenge for even the most seasoned technician. Several years ago, I wrote a selection of GEARS articles explaining the theory, diagnosis, and repair for common vibrations faced by most shops. The nice thing about vibrations is that they...

Bushings: How Critical Can They Be?
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Like many components used in the transmission industry, the term bushing can be described using various other names. A plain bearing, sliding bearing, solid bearing, or friction bearing are all terms used to describe what many of us refer to as a bushing. Bushings, like bearings, have been around longer than the automobile and are used in various industries. Bushings are compact, lightweight, h...

Cool It: What You Need to Know about Your Vehicle's Cooling System
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A recent study found that up to 40% of all engine failures were a direct result of cooling system issues. As the vehicles we service continue to evolve, the coolants and systems designed to keep our transmissions and engines operating at the correct temperature are also changing. Many of the changes have led to confusion at the repair shop level. For decades, vehicles used ethylene glycol (gree...

What's Causing That Shudder? A Deep Look at a Misfire Issue
As today’s vehicles continue to become more complex, the problems we face also tend to increase in complexity. Several years ago I wrote an article about the “new direct-injected gasoline engines” that were just being introduced. Since then, most direct injected engines have added turbochargers, superchargers, variable cam timing, and now variable lift camshaft technology. Volumetric effi...

A Common Sense Approach to Charging System Diagnosis
In the previous article, we discussed the issues and operations related to the charging systems in common use today. Charging system problems may cause various vehicle issues, such as transmission shift and pressure control problems, DTCs, and driveability-related complaints. Testing the charging system is fairly straightforward if you understand how the system operates. A voltmeter, scan tool,...

High Output: A Look at Today's Charging Systems
The longer I’m around, the more I realize the importance of the basics. How many times have you tackled a complex vehicle issue, only to find the problem was something really basic? With each year’s seminars, I find that we likely have some information that deals with system powers and grounds. The more complex the system, the greater the need for a proper power supply and ground. Vehicl...