Just how serious is a transmission leak? For the most part, how quickly the transmission fluid is leaking is going to play a large part in that. It also matters a great deal where the transmission is leaking from.
Please be aware that transmission fluid is flammable, and will flash if it hits the exhaust manifold or header. So if you have it leaking onto there (usually out the dipstick) it should be dealt with immediately. Thankfully, this scenario usually happens only while towing or if the transmission has been over filled. Here’s a great resource on ATF flammability.
If you are leaking transmission fluid from the pan directly onto the ground, the transmission leak is not that serious unless the vehicle is hemorrhaging it. If it is, than it’s serious because running out or running low can cause some serious problems. Here are some common signs of low transmission fluid.
Don’t let your transmission run out or low
If the transmission is losing a quart or so every thousand miles, that’s going to be manageable. But, if you’re losing a quart every time you drive the car, that’s going to be a real problem, especially if you let the fluid level get too low.
When the transmission fluid level gets too low the transmission will begin to slip. This means that there is no longer enough fluid in the transmission for it to do its job as a hydraulic fluid that conducts energy from the crank through to the axles/driveshaft. Here’s more on transmission slipping diagnosis.
Once it begins to slip, the transmission will begin to wear at an unusually high rate. This is due to the transmission fluid also being a lubricant and acting as a coolant as well. Once you take away the lubricant and you let the transmission overheat, it begins to wear at an incredibly fast rate, and will soon not work at all.
Is it safe to drive with leaking transmission fluid?
If the transmission is leaking directly from the transmission pan (far and away the most common area) than it is safe to drive. That is unless it is just totally going through transmission fluid. Enough transmission fluid leaking anywhere can be dangerous. But, if you have a few drops showing up on the garage floor, and it only needs topped off now and then, it’s going to be safe. When in doubt, don’t drive a vehicle that you don’t feel comfortable driving, especially if you are smelling a burning smell.
A little leak now will often become a big problem later. Do yourself a favor and have it fixed. It’s not as difficult or expensive to fix a leaking pan gasket as you might think!