If you’re having trouble with your automatic transmission, there are a few things you can try before taking it to a mechanic. Always bear in mind that it’s important to know your way around a vehicle before trying to do anything to fix it. If you are not mechanically inclined, exercise caution in trying to teach yourself how to do any kind of repairs.
These tests can help you figure out what the problem is, or is likely to be. Try them out for yourself if you have the skillset and are so inclined.
The Stall Speed Test: Transmission Problem vs. Engine Problem
If you think you have a problem with your automatic transmission, it might be a good idea to check and make sure it isn’t a problem with the engine first. The test is actually very simple: you need to run the engine while the car is braked so that you can get a reading of the stall speed from the tachometer.
To conduct the test, make sure you’re in a safe area with a lot of open space, so you won’t run into anything if something goes wrong. The parking brake needs to be set. Turn on the engine, go into drive or reverse, and then floor the gas and hit the brake. Watch the tachometer and note how high the RPMs go. Do not exceed a few seconds!
The main thing here is to discover if the problem is with the engine or with something else, perhaps the transmission. If the engine is at fault, the problem will manifest during this test. If it is not the issue, the problem should not manifest—and you can conclude that there is a good chance that it is the transmission. The RPMs, while good to note, are actually a secondary consideration.
The Filter and Pump Test
If your transmission simply will not budge, there is something else you might want to try. It is possible that the issue is your pump, and you can test whether this is the case by giving your pump a chance to prove itself.
First, find a transmission cooling line and loosen it. Don’t take it all the way off, just loosen it enough to allow it to leak. Take a rag and wrap it around where you’ve loosened the line so that you don’t spray fluid everywhere. Now, start your engine and run it for a few seconds. If your pump is working, it will spray automatic transmission fluid. If there is no spray, your pump is probably the issue.
One last thing to try is checking the transmission filter. A filter that has been plugged by detritus could also be responsible for the low pressure situation. For more information visit Trans Works Transmissions.