Symptoms of a transmission problem. There are may different symptoms that you might experience when your transmission is having problems, some of them are specific to manual transmissions, some of them are specific to automatic transmissions and some of them can kind of span the two. A common problem in manual transmissions is that the syncromeshes can wear out and what will happen is that between gear changes you can get a grinding or the gear may not stay in if you're coasting or under loaded and will try and pop out of gear. These are usually an indication that the syncromeshes are worn. You might be getting excessive gear noise or difficulty shifting and that can often indicate that either you are due for a fluid change or the fluid level itself is too low. If that situation is not dealt with ultimately you can damage the transmission and then it will require a complete overhaul. In the case of automatic transmissions you can experience similar issues where if you are getting excessive gear noise coming from the transmission there is the likelihood that the fluid is either low or contaminated and it is ready for a service. If the transmission is slipping then it could be related to the fluid. It could also be a problem with the clutch bands. They might be excessively worn or out of adjustment so they are not able to engage the gear properly. You could also have debris in the valve body which is preventing it from sending the fluid where it needs to go. Lastly with an automatic transmission if the fluid is burnt you can actually smell a burnt smell if you pull the dipstick out and smell the fluid. That is an indication that there is excessive friction occurring within the transmission, either the transmissions is being used harder than it was originally designed to be used or there are components that need to be serviced. If you are towing with a vehicle or racing a vehicle you want to make sure that the transmission has been built to handle those circumstances and has sufficient cooling so that the fluid remains at its optimal operating temperature.