What happens when you accidentally shift into neutral, at 60 mph? It's not pretty.

Dear Car Talk

Dear Car Talk | Aug 01, 2008

Dear Tom and Ray:

I accidentally shifted my 1999 Plymouth Grand Voyager (SE 6-cylinder) into neutral while the car was in motion at 60 mph. I put it back into gear and heard a loud noise, and the car bucked like I had rolled over something. I know, not good. I pulled over because the car had shut off. I started it again and stepped on the accelerator. The engine just revved. I got out and saw transmission fluid leaking onto the ground. What the heck happened? And please tell me I don't have to get a second mortgage to fix it! Thanks in advance, and cheers! -- Greg

TOM: Oh, Greg. Why don't you go grab the home equity loan application, and then come back and read the rest of our answer?

RAY: I'll tell you exactly what happened. When you "accidentally" shifted the transmission into neutral while you were traveling at 60 mph, you also "accidentally" overshot neutral and shifted it into reverse.

TOM: That's what happened, Greg. That explains the loud noise, the bucking sensation and the subsequent and immediate lack of a functioning transmission.

RAY: When you shifted into reverse at a high speed, you probably blew apart the spider gears in the differential and blew a hole in the differential casing -- which is part of the transmission housing. That's why transmission fluid was pouring out under the car.

TOM: So, you're looking at spending somewhere north of $2,000 on a rebuilt transmission if you ever want this car to move under its own power again, Greg. This is one powerful reason not to shift the car into neutral while your car is moving, unless it's an emergency -- like your throttle is stuck.

RAY: Right. We've heard from a lot of people who think they're improving their mileage by "coasting" in neutral occasionally. But the few cents they save on gasoline will pale in comparison with a new transmission if they accidentally push the shifter a smidge too far.

TOM: Actually, not all cars will suffer the same fate as yours, Greg. With all of the electronically controlled automatic transmissions these days, there are a lot that simply won't allow the transmission to shift into reverse when it's not safe to do so --like when you're going forward at 60 mph.

RAY: Unfortunately, we now know that the '99 Voyager wasn't one of those. But the truth is, we don't know exactly which transmissions will protect themselves and which won't. We can't really experiment on the brand-new test cars we drive, can we?

TOM: So, if any of you readers have "accidentally" experimented on your own car, let us know what happened (at www.cartalk.com). And next time my brother lends me his car, I'll tell you what happens when you put a '97 Honda Odyssey in reverse while going 60.

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