Dear Car Talk:
I have two automatic transmission questions that have plagued me for over 50 years.
1. Is it OK to coast in neutral with an automatic transmission? I am asking from a potential damage problem, not the safety aspect.
2. Is it OK to tow an automatic transmission car on its drive wheels?
My father always taught me that it would ruin the transmission to do either, but I see cars being towed all the time on their drive wheels. Please help clear this up for me! — David
Your dad was one for two, David.
Coasting with the engine running and the car in neutral won’t do any damage to an automatic transmission. The reason it’s discouraged is because if you’re coasting down a long or steep grade, you lose the car’s natural engine braking.
That can allow your speed to get out of control or force you to overuse, and therefore overheat, your brakes. Overheated brakes can fail, which is always bad news, but especially unwelcome when you’re heading down a long hill at high speed.
On the towing issue, your dad was correct that a car with an automatic transmission should not be towed with its driven wheels on the ground, even in neutral. The reason you can’t do it is because the driven wheels on the ground will turn the drive shaft, which will turn the internal parts of the transmission.
And an automatic transmission only gets lubricated and cooled when the engine is running. So if you tow it like that for any real distance at all, you’d likely ruin the transmission.
Fortunately, the majority of tow trucks now are flat beds, which lift the car completely off the ground for towing. That’s in part because so many cars and crossovers are now all-wheel drive. And if all the car’s wheels are driven wheels, there’s no other way to tow it. It’s also just safer than having a car bouncing along behind a truck. So flat bedding is what we’d always recommend if you’re getting towed. That’s always a safe option.
Got a question about cars? Write to Car Talk write to Ray in care of King Features, 628 Virginia Drive, Orlando, FL 32803, or email by visiting the Car Talk website at www.cartalk.com.
