by Sam Dillinger (comments: 0)

Why Are Transmission Repairs So Expensive?

internal transmissio repair

This is a question that I get asked on a pretty regular basis, why are transmission repairs so expensive? There is a long answer (really long, technical, and boring, actually) and there is a short answer. First, the short answer: difficulty. By difficulty, I mean the difficulty of diagnosing the failure in a transmission. Believe it or not, taking a transmission apart, and putting it back together, isn't as hard as you think. It’s similar to a jig saw puzzle. There are a bunch of strangely shaped pieces that don’t appear to have any intelligent design, and don’t seem to fit together at all. Once you get passed that, and the monumental task of removing the transmission from the vehicle, rebuilding a transmission is a cinch! In all actuality, rebuilding a transmission is slightly easier than the diagnosis, but it’s still pretty complicated. Back to the question at hand though, the difficulty in diagnosing a transmission problem stems from the fact that you have 3 systems working together to make the transmission operate. Any of the 3 can fail and act exactly like one of the other 3 is at fault. Let me explain.

First, there is the electrical system of the transmission. In older vehicles there was either no electronics, or they were very limited. In the transmissions of today’s vehicles, everything is electrical. You've got a computer that watches all of the sensors, commands the shift solenoid to change the clutches that are being applied, learns the driving habits of the person driving (no I’m not joking, they really do learn your driving habits), and a bunch of other tasks. As well as, speed sensors, shift solenoids, range sensors, neutral safety switches, fluid pressure switches, and much more. When any part of the electrical system fails, you get what’s referred to as “limp mode”. This means that you've got one forward gear, and reverse. A quick note about reverse, it’s always hydraulically or mechanically controlled, so if reverse doesn’t operate, you've got a serious internal failure. Back to the electronics. When you're transmission goes into “limp mode”, the check engine light will come on, and you'll get a vague sounding DTC that gives you next to nothing, as far as helpful information. Something like this “P0750- Shift Solenoid A Malfunction”. That’s not going to be very useful to you to know that code. To make things even better, there are usually several codes present. They may all refer to the same problem, but it’s also somewhat likely that there is more than one problem being represented by these DTC’s. All you need to do is figure out how many issues are present, and how to fix them. More about that in a minute.

Second, is the hydraulic system of your transmission. This is a part of your transmission that is extremely technical and boring. I won’t waste much of our time together, making your brain hurt with all of the technical information contained in hydraulic operating theory. There are a few important things to know about it though. The main one is this: a liquid cannot be compressed. This is the entire idea behind making a fluid do your bidding. You can squeeze it as hard as you want, and it won't shrink in size or volume. Instead it will move to the area of the least resistance. So when you pressurize a liquid, and give it a defined path to travel, it will be able to accomplish a variety of tasks like: clamping, moving an object, inflating a bladder, and one of the most important, lubrication, to name a few. The fluid in your transmission is it’s life blood. Without it, you won't be going anywhere.

Third, is the mechanical system. This is the part that most people have seen, at least a little bit. This is all of the actual metal pieces of the transmission itself. The gears, the clutch packs, the valve body, the pump, the torque converter, the case itself (most likely this is the piece you've seen), and a few more. The mechanical side of the transmission is just as complex as the other 2 pieces of the transmission. There are planetary/sun gear/annulus gear assemblies that allow the transmission to use different gear ratios. The different gear ratios are how the transmission computer, or TCM, electronically knows what gear is being used.

Now that I’ve given you the brief description, and trust me it is brief, I’ll circle back around to the main point of discussion. Transmission repairs are so expensive because of the diagnosis involved in figuring out which part of the transmission has failed. For instance, assume you're driving along on your way to work, and you've come to a stop at a red light. When you take off from the light, you make it from first to second gear smoothly, but when your transmission tries to shift to third gear, the engine revs really high and you can feel that you're not accelerating anymore. After all the cuss words, and the tow truck as well, there has to be an answer for what happened. It can literally be any of the 3 systems that have caused you this heartache. The shift solenoid could've failed (electrical), a valve in the valve body could've gotten stuck, causing third gear to go into hiding (hydraulic), or the seal for the piston that applies third gear in your particular type of transmission, could've just blown out (mechanical). Any of these 3 scenarios is just as likely as the other. All can cause the check engine light to come on, or not. Realistically, the check engine light should come on if the solenoid were to fail, but it won’t always. As an added bonus, there are somewhere around 50 types of transmissions in use in cars today. They all share some of the same components, and some of the same theories of operation, but they all have differences as well. An engine is an engine no matter what. Whether you've got 4 cylinders, or 12, it’s still an internal combustion engine, and they function the same across the board with very little internal difference.

So when you've found yourself encumbered with a transmission problem, you'll find there are a lot of people with guesses and opinions, but surprisingly few that have valid answers. Unfortunately, this is true for a lot of so-called experts as well. Guessing seems to be the most popular way to fix transmission related issues because it’s drastically easier. To properly diagnose the failure, you've got to use fluid pressure testers, electrical diagnostic tools, plenty of brains, and a healthy dose of experience. It can take several hours to correctly diagnose a problem with any of these 3 systems, and the parts alone are almost never cheap. For these reasons, you’ll find that anyone who's good at transmission repairs will not be cheap with their labor. With this in mind, I can tell you that it’s worth the money to pay a certified, trained, professional to diagnose and repair your transmission correctly, the first time.  You may spend a little more than you would if you had the local “Joe’s garage” attempt the repairs, but in the long run, it will be cheaper for you to only pay for the repairs once instead of paying for someone to guess at what might've happened. Thoughts? Comments?

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Meet Sam Dillinger

My name is Sam Dillinger. I've been a professional, dealership technician for 18 and a half years. My first introduction to mechanical repair was when my own vehicle broke down in the fall of 1995. I was 18 and couldn't afford to pay to have it fixed. So I borrowed tools and asked a ton of questions and, eventually, was able to replace the clutch on my truck by myself. During the course of that project, I found that I really enjoyed having a wrench in my hand and figuring out the puzzle of disassembly and reassembly of a motor vehicle.

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