How to diagnose transmission problems?
The moment you feel your car transmission slipping , your heart skips a beat in the same moment then you say to yourself, here go transmission problems ugh . If you’ve been driving for 10 or more years, then the likely hood of you having to repair or replace a transmission before is an expensive experience you’ll never forget.
Your reading this post so you must be experiencing transmission problems. You’re in good hands because today you’ll learn step by step on how to diagnose transmission problems even if you’ve never been under the hood of a car ever.
Today you will learn step by step how to do automatic transmission troubleshooting and manual transmission troubleshooting.
Alright, let’s begin. First, allow me to educate you a little why cars do what they do.
what causes a transmission to slip?
Automatic transmission
- worn mechanical parts i.e transmission gears
- worn electrical parts i.e sensors, car computer, transmission control module
- low transmission fluid
- Lack of maintenance
- Electrical short in car i.e deteriorated wires inside transmission and connected to the exterior of the transmission, car ECU
Manual transmission
- Worn mechanical parts i.e gears
- worn electrical parts i.e sensors, and transmission control module
- worn clutch assembly
- low transmission fluid
- Electrical short in car i.e deteriorated wires inside transmission and connected to the exterior of transmission, car ECU
Automatic transmission troubleshooting
The first step in automatic transmission troubleshooting is verifying that the transmission fluid level is at its full level. Tools needed for checking the transmission fluid is minimal. you just need a napkin or an old rag.
Here’s how to check the transmission fluid. Some cars and trucks have what is called a dipstick. Some cars and trucks don’t have a dipstick and transmission fluid level are checked from underneath the vehicle. To find out if your car has a dipstick or not you will need to look under the hood of the vehicle for a dipstick that will be marked trans.
If you want to take the most precise route of finding out where the where the trans dipstick is located you will need access to an online car repair manual. I’ve been using this easy to understand online car repair manual for the past 12 years. You will need to create an account and pay a small fee to get access to the information for your specific car. The sign-up process has only 10 pieces of information to fill out, it’s really fast . I paid only 25.99 for a year’s access which is fairly inexpensive. Head over there and get the information for your vehicle.
In the past, I’ve tried to use Google to get information on my cars that I was working on, and it took me hours just to figure out simple information, and I was even misled by people that had no idea about what they were talking about. I could have just gone straight to a reputable source.
Once you’ve figured out what the transmission level should be at, the next step is to check to see if the check engine light is on. Warning just because you do not see a check engine light on, that doesn’t mean there isn’t any engine codes or transmission codes.
I know you’re probably saying I don’t have access to a car code scanner, but if you stick with me I’ll show you how to get access to one without breaking the piggy bank.
Transmission fluid low/leaking common areas to check
- Transmission line leak
- Transmission tail shaft seal leak
- Transmission front seal leak
- Transmission axle seal leak
- Transmission leaking from torque converter
- Transmission case leak
- Transfer case leaking transmission fluid
- Transmission cooler line fitting leak
- Transmission cooler leaking into radiator
How to check transmission fluid on automatic transmission
The most general way to check the fluid on an automatic transmission is to start the vehicle put it park and pull the dipstick wipe it off and insert it again to see the fluid level, and color of the fluid. If the automatic transmission fluid has a nasty smell like it’s burned, that’s a sign fluid was overheated.
Some vehicles automatic transmission fluid is checked in neutral while the engine is running. Some vehicles have instructions written on the transmission dipstick on whether to check the transmission fluid in park or neutral. The Honda Acura brand, you have to start the vehicle then shut it off to check the transmission fluid. Remember this is just a general procedure for checking fluid on an automatic transmission, and you’ll need to get access to an online car repair manual.
Types of automatic transmission fluid
There are many types of transmission fluid, but I am going to list the most generally used types of automatic transmission fluid.
- Automatic transmission fluid
- CVT fluid Continuously variable transmission specifically engineered for CVT transmission
Be certain that you do not put the incorrect type of transmission fluid doing so will cause damage to transmission components. As stated before one of the ways to find out what type of transmission fluid your vehicle uses is to use an online car repair manual.
what color should transmission fluid be?
Automatic transmission fluid that is in good condition will be cherry red. Take a look at the image and you’ll have an idea of what to look for in when checking the fluid and after you remove the transmission pan.
Next, you will need to get access to the transmission pan. If you don’t know the first step to removing the transmission pan, then you’ll need to find out through your online car repair manual. What you are going to do is remove the transmission pan and save the fluid for further inspection. Inspect the transmission pan and pan magnet for metal fragments.
I do not own these images their sole purpose is to be used as examples.
(TRANSMISSION OVERHAUL RECOMMENDED)
The image above represents transmission fluid mixed with coolant and is a really bad sign.
(TRANSMISSION OVERHAUL RECOMMENDED)
The image above represents an automatic transmission pan with the worn clutch material.
(TRANSMISSION OVERHAUL IS RECOMMENDED)
This image represents worn clutches and gears.
(TRANSMISSION OVERHAUL IS RECOMMENDED)
This image represents broken transmission components inside of the transmission. If you see any of these examples while inspecting the transmission, then transmission overhaul or replacement is needed.
How to read transmission codes
Knowing how to read transmission codes is vital to your diagnosis. Don’t get discouraged, it not as complicated as people make it out to be. If you can read, you can figure it out trust me. To read any check engine light or transmission codes, you will need a car code reader. Even if you see no codes present, you will still need to scan the transmission anyhow because codes could be pending. THIS STEP IS VERY IMPORTANT. DO NOT SKIP THIS STEP.
Remember earlier when I told you I was going to show you how to get access to a car code reader without breaking the piggy bank? If you have ever seen a code reader that car mechanic use you know that they are bulky and hard to use. This code reader that I am about to recommend to you is called BlueDriver – Bluetooth Professional OBDII Scan Tool for iPhone®, iPad®, Android it’s easy to understand, and you use your smartphone as the car code reader.
This car code reader has all the bells and whistles features that $8,000 code reader has. The blue driver car code reader is an app that you can use on your phone. See today’s technology has allowed us to play with the big boys on a small budget.
All you need to do to use this as a car code reader is download the free app. You also need to purchase the blue driver sensor. The blue driver product has over 300 reviews on amazon with a 41/2 star. All the information about the BlueDriver – Bluetooth Professional OBDII Scan Tool for iPhone®, iPad®, Android is on amazon. just click the image below to read all about it.
False transmission problems
When your vehicle starts to jerk and skip a beat as if it has a transmission problem, it may not be a transmission issue. If the check engine light is on, you need to address the check engine light first. If upon checking the codes and find any codes that say miss fire on the engine side and no codes on the transmission side, the miss fire codes needs to be fixed first. Correction, if there is also transmission codes on the transmission side still fix the miss fire code first.
(Real life case study) How to read transmission codes and repair the problem
(Case study #1)
A 2008 Volkswagen wagon Jetta 2.5 was towed into the shop from a used car dealer. The car was banging in gears while driving. Every car that comes in with a transmission problem is diagnosed in this same order, and I highly recommend you do the same. The first thing we did was check for any error codes or check engine light, and saw the check engine light was illuminated.
We place the car code reader on the car and retrieved a code for the turbine speed sensor. We checked our online car repair manual to see where it was located. We found out the turbine speed sensor is located inside of the transmission ugh. We checked to see if we could access the turbine speed sensor without removing the transmission.
Well, we were in luck. In order to replace the turbine speed sensor, we would have to remove the valve body. In this scenario really, the speed sensor may not even be the issue. There could possibly be a short meaning the wire that feeds the turbine speed sensor with its power or ground could be broken. We thought it was worth a shot because sensor fails all the time. We followed the instructions from our online car repair manual and replaced the turbine speed sensor.
Wen we put everything back together we placed the car code reader back on the car to see if any codes were present and to our surprise, there it was the same code that we started out with was still there. We wanted to be for sure so we erased the code and took the car for another test drive.
The car was still banging in gears while driving. We scanned the car and the code was back now it was confirmed for sure a wiring issue now. The next step we checked the transmission wires and connectors for damage. Bam, we found the problem.
A wire that feeds into the transmission harness was broken completely, and all we needed to do now is order a new main connector and wire pins. We spliced the wires and re-pined wires to its appropriate places. Rescanned the car and test drove it, it drove beautiful.
What caused the transmission wire harness to break?
Under the hood of the car is exposed to extreme temperatures as high as 180 degrees. We all know that anything exposed to that type of temperature over an extended amount of time has an increased chance of deterioration to the wire harness and sensor, it dry rot and fall apart.
In this case, what we usually do is clear the code and test drive the car again to see if the code comes back. If the code comes back then you have a problem for sure. Next, we verified that the transmission fluid level was full.
This car’s transmission fluid level is checked from the bottom of the car. You start the car then remove the plug and while the engine is running and if fluid drip’s out, then it is considered full as it was stated in the online car repair manual. Once the fluid level was confirmed full, and inspection around transmission pan and lines were not leaking, now it was time to get access to the transmission pan to look inside and inspect it.
Next, we removed the transmission pan and found no signs of metal and clutch material on the transmission magnet.
(Case study #2)
My 2005 Dodge Durango 3.7 was shifting harshly through the gears. The first thing I did was check the transmission fluid level. The transmission fluid was at its level. There was no need to check for any leaks. next, I decided to diagnose the problem thoroughly and scanned to see if there were any check engine lights on or pending. To my surprise there was codes tcc code for torque converter clutch and a few others that I can;t remember.
Being that I worked for a transmission shop and had veterans that work there too, the transmission builder assisted me in my diagnosis. He looked at the codes and then at my transmission data. There is this one specific data that he was very adamant on checking to be sure the transmission was not hurt too badly. The data subsection is called the CVI value aka the clutch volume index.
In a simple explanation, the CVI value should not be over 150 total. my CVI value was 157. Not horribly bad but because I had the codes it was not shifting properly so that’s the reason for the extra 7 points. If the CVI value was in the 190 range than definitely the transmission is hurt.
Being that the builder has seen these values before, he knew what to recommend replacing. He recommended that I replace the solenoid pack inside of the transmission. I check my online car repair manual to see if I had to remove the transmission to replace it and found out I could do it without removing the transmission.
There was a known good solenoid laying around the shop. I cleaned it up and changed the solenoid pack, filter and gasket. I inspected the transmission pan and magnet and found normal wear and tear. No big chunks of metal, I was super happy. Reprogrammed the transmission adaptive values. This has to be done to reteach the transmission to drive normal and not duplicate its old condition.
I got in test drove the truck, and it drove as it was brand new again.
Removal of the transmission valve body and solenoid pack
valve body and solenoid pack. solenoid pack is the thing that has green rubber around it.
Old solenoid pack removed from valve body
My transmission pan is pretty clean. The magnet has a little wear and tear metal on the magnet.
Manual transmission troubleshooting
In order to do an accurate manual transmission troubleshooting, you first need to take note of any check engine light on or error warning on the instrument cluster. Remember even though you may not see in error messages or check engine light, you will still need to scan the vehicle with a car code scanner. Why? because codes and error messages could be pending and you will be able to see still see them with the car code scanner.
The next step is to get access to the manual transmission fluid. If you do not have a clue where to check the transmission fluid you will need to get access to the online car repair manual.
How to check transmission fluid on manual transmission
Checking the fluid level on a manual transmission is a much different process. Manual transmission, you do not need to have the car running in order to check the transmission fluid. There is no dipstick to check the transmission fluid.
Most manual transmissions fluid level is checked from the bottom of the vehicle. The manual transmission has two plugs, one to drain the transmission fluid and the other to fill. The fill plug is mounted higher on the transmission case housing than the drain.
To generally check if the manual transmission fluid is at its level, you will need to remove the fill plug to see if any liquid comes out. If fluid comes out its full, If no fluid comes out then its low on fluid or empty. This is just a general procedure to check manual transmission fluid level. To find the process for your vehicle you will need to get access to an online car repair manual.
To get a better prognosis of the transmission’s health you will need to drain the fluid just as we did for the automatic transmission. When the fluid is drained into a clean container inspect the fluid to see if there are any metal shaving in the fluid. What you can also do is strain the manual transmission fluid into another container to see the amount of metal shaving that is collected in the strainer.
Manual transmission fluid color inspection
Take note of the color of the transmission fluid. It all depends if you change manual transmission fluid on time dictates how dirty it will be. Manual transmission fluid should not have a silver lining in it. If it was a silver look to it, the transmission is wearing on the inside.
Types of manual transmission fluid
There are different types of manual transmission fluid. One type of fluid is MTF which looks similar to engine oil, and some manual transmission uses your regular automatic transmission fluid. Refer to an online car repair manual to find which type of manual transmission fluid your vehicle uses.
Should I buy a used transmission or rebuild my transmission?
Based on the amount of damage that is done to the transmission, it is sometimes necessary to buy a used transmission from a salvage yard. If you choose to go this route,you will still need someone to install the transmission for you. If you use a transmission shop to install most like they would source out a used transmission from a salvage yard and give you a warranty. You can still buy it yourself, but the transmission shop will most likely not give you any warranty.
If you want to buy a used transmission from a salvage yard be sure to ask how many mile is on the transmission. I know that salvage yards do exaggerate the truth also so be sure to have that salvage yard remove the transmission pan and let you have a look inside. follow the same criteria for inspecting the transmission pan.
I really can’t say no to buying a used transmission from a salvage yard because every transmission situation is different. I will say this though if you go through the diagnosis process and the pan inspection for the automatic transmission is clean meaning no metal in the fluid, then rebuild the transmission. The same goes for the manual transmission fluid inspection.
How much does a used transmission cost from a salvage yard?
Most salvage yards have transmissions available with prices ranging from $400-$2500. again every car is different. it depends on the make and model of the car. Generally, auto repair shops get the best price so use a repair shop to get a better deal
How much does it cost to rebuild a transmission?
Average transmission repair cost can range from $1800 to $5000. It all depends on the vehicle you are driving.
(Real life example) I have seen a Mercedes-Benz transmission rebuild cost $4000 why because Mercedes-Benz has a valve body that goes bad. To repair the valve body you need a new valve body that cost $1000 and it needs to be reprogrammed with new software, and it cost $2000 to install and program the software. Generally, the European cars parts cost more than Asian and American vehicles.
Conclusion
Transmission problems drain your bank account ,and it drains your energy. it doesn’t have to be that bad now that your arm with information that will give you a piece of mind. Always remember whether it’s a manual transmission or an automatic transmission to diagnose the problem in this order.
- Verify there is check engine light. if no check engine light is lit, still scan to see if there are any pending codes.
- verify fluid level
- check for leaks
- Drop transmission pan/ drain fluid to inspect pan and fluid
- Use your online car repair manual for assistance
- check wire harness and connectors for broken wires and corrosion
- Repair problem is it is not too difficult to get to
Are you having transmission problems? I want to know the year make and model and give me more details about the symptoms. Leave your questions in the comments, and we’ll answer your questions.
