Is low gear a no-no... and is the transmission in Marilyn's minivan now toast? Find out.

Dear Car Talk

Dear Car Talk | Feb 01, 2007

Dear Tom and Ray:

Is my transmission destroyed? My daughter-in-law drove my minivan in low gear at speeds of up to 40 mph for several hours yesterday. I was giving her a driving lesson, and she thought I said it was "safer" to drive in low gear. I actually had told her to put it in low gear while we were coming up the steep hill of her driveway out of her backyard. I learned about this at the end of the day when I asked her to put it in low gear to drive back down the driveway hill. She told me she had been driving in low gear all day. I have never driven the car faster than 5 mph in low gear. What damages should I be looking for? -- Marilyn

P.S.: My son says it was all my fault.

RAY: Well, it is all your fault, Marilyn. That's the bad news. The transmission is automatic. That means it goes into low gear automatically whenever it needs to -- it doesn't require driver input to tell it what to do.

TOM: Especially for a new driver. There's enough to think about without toying with the transmission. So if it's an automatic, just put it in drive and leave it there.

RAY: The only time you'd want to put an automatic transmission in low gear yourself is when you're going down a long, steep hill and you want to keep the brakes from overheating. But your average driveway is not what we'd consider a long, steep hill. We're talking about hills that are miles long, not feet long.

TOM: But the good news is that your daughter-in-law didn't do any damage. Modern cars are electronically prevented from going over the maximum engine speed in any gear. In fact, some transmissions are even smart enough to ignore stupid human input.

RAY: For instance, on all DaimlerChrysler four-speed transmissions that have "D3" and "LOW" on the shift indicator (which is what you'll find on their Dodge and Chrysler minivans), when you put it in low, it'll automatically shift to second gear at 35 mph to prevent someone from accidentally leaving the car in low gear and ruining the engine or overheating the transmission.

TOM: So my guess is that no damage was done. But since you guys drove around for hours, running the car at fairly high rpms, it wouldn't hurt to ask your mechanic to check the transmission fluid. If it smells like my brother's cooking -- i.e., burnt -- then it turns out you did heat it up pretty good, and it needs to be changed, along with the filter. In that case, I'd change the engine oil and oil filter at the same time.

RAY: But I'm guessing it's fine, and you can forget all about it.

TOM: Don't worry about the kids, either. Despite your son's ire, I'm sure your daughter-in-law is very grateful that you took the time to try to teach her how to drive. That was a loving gesture. And I'm sure that in a decade or two, she'll allow you to speak to the grandchildren again.

Get the Car Talk Newsletter

Got a question about your car?

Ask Someone Who Owns One