There comes a time in the life of any mechanical device, no matter how well maintained, that it’s going to go out. Transmissions are certainly no exception. They are full of complex parts that just wear out eventually. Knowing when your transmission may be going out is a great way to keep from getting stranded somewhere.
Here are the prime signs that a transmission is going out:
This is a general term for when a transmission is revving faster than it should be at any given vehicle speed. This could be a sign of a bad torque converter, or it could be the clutches in the transmission itself are going out. There can be other less common issues that cause this as well.
There could be a number of reasons why it would slip. I always advise people to explore their diagnostic options weighing cost/difficulty. If your automatic transmission is slipping, you should get it to a flat surface and check the transmission fluid.
Now if the fluid is barely registering on the dipstick, you’ve found your problem. Even if it is full, you may have cooked your transmission fluid. make sure you understand what transmission fluid color means. If it’s dark or sooty, you may need to change it out.
For more on this: Transmission Slipping Diagnosis
The Smell of Rotten Eggs
Beware an egg like or sulfury smell coming from your transmission. This is one way to know your transmission may be going out. The egg smell is the smell of clutches slipping and burning.
If this is the case for you, as quickly as it is safe, check your transmission fluid level. If there isn’t enough fluid to meet the minimum needs of the transmission, parts can burn quickly. A few minutes of driving can cause years of wear and tear on the vehicle. For more about low transmission fluid, here are the signs of low transmission fluid.
If you have a manual transmission, the smell of eggs comes when you burn up the clutch. Burning up the clutch does not mean that you’ve necessarily ruined it though. It could mean that it has been slipped enough that it’s too hot. This can occur from driving to aggressively, or when a person first starts driving stick. Give it a bit to cool off and see if the clutch grips good again.
On the other hand, if the slipping occurs at highway speed (or under a heavy load) with your foot off of the clutch, this is a huge sign that the clutch is going out. The clutch is certainly part of the transmission, but is made to be replaced and is certainly cheaper to replace than an entire transmission.
With an automatic transmission, if the transmission fluid is full, than the slipping can either be the clutch packs going out in the transmission, or it can be a bad torque converter.
Limp Mode and/or Faulty Sensors
Often, a transmission will bring itself into limp mode to save itself from really getting hurt. Depending on the vehicle, limp mode could mean one of many things, but it usually means that some sensor in the transmission is picking up a pressure reading that is very much off.
The best thing to do if this has occurred in your vehicle is read the trouble code that the ECM throws. You can use an OBD III scanner, or you can run your vehicle up to an auto parts store. They almost always scan these trouble codes for free (they get paid when you buy the part). They’re also pretty cheap on Amazon.
Now if you’re lucky, the sensor in question is located on the outside of the transmission and you won’t have to drop the pan in order to replace it. Japanese cars are great about keeping many sensors on the outside, for instance.
It could always be a shorted out wiring harness too. The good news about that is that they are super cheap to repair. The bad news is that finding shorts is an incredibly difficult task. If the transmission problems seem to come and go at different times with no apparent rhyme or reason, you should look into whether it’s a short. Here’s a great resource on just that from Popular Mechanics.
Here’s more on limp mode causes.
If your transmission is dumping fluid all over your driveway, it’s a pretty good sign that something is wrong. Leaking fluid can be a symptom of many problems. Such as:
- Loose torque converter- Usually if this is the case you may have noticed some sort of vibration at highway speed. Depending on the vehicle, this may or may not be easy to check. For more on bad torque converters check out Signs of Torque Converter Problems.
- Loose lines- There are coolant lines that carry transmission fluid to the radiator from the case in every automatic vehicle. They are usually hard lines and not prone to breaking, but it is possible. They can also work loose. If you detect a leak from one of these lines, make sure that you clean it and find exactly where it is coming from. Trans fluid can travel a long way on the bottom of a line until it reaches the lowest point to fall off.
- Pan gasket failure- Over time it is possible for the transmission pan gasket to fail. This was really a problem whenever manufacturers relied upon cork gaskets. If you have to replace one, go ahead and make sure to put a rubber one in.
Hesitation Going Into Gear
If the car or truck has a couple mississippi delay before going into the gear that you have just selected, than it is very likely there is something wrong with the transmission.
A service engine soon light is not a “dummy light” as some people like to call them. It is a way for the intelligent and complex electronics that control your engine and transmission to let you know that there is something wrong. Don’t ignore it.
It can be really tough to determine if your transmission is going out. The signs listed above can certainly help you make a decision about whether yours is.
You know your car better than anyone. Typically, if you feel there is a problem, there is. Don’t ignore it.