My bride of 17 years has PMS and handgun.

Dear Car Talk

Dear Car Talk | May 01, 1992

Dear Tom and Ray:

My bride of 17 years has PMS and a handgun, and she's insisting that you answer this question for us. We have a Mercury Sable and a Volvo 740 GLE. Both have automatic transmissions. Both have a "High Drive" position, and a "Low Drive" position. We've had mixed information from salesmen and mechanics on both cars about when to use "Low Drive." Some tell us to use "Low Drive" for any city or hill driving under 35 mph. Others tell us to use "High Drive" all the time and don't worry about it. What should we do? Did I mention my wife has PMS and a handgun, and she wants an answer to this now??

TOM: Tell your bride that this is a great question, Joe. Given the circumstances, we would've said that no matter what she asked. But this actually happens to be a question a lot of people wonder about.

RAY: Your shifter has four forward positions; "1," "2," "D," and "D" with an "O" around it. The "D" with an "O" around it is overdrive----essentially the fourth gear on a four speed automatic transmission. That's what you refer to as "High Drive." And it should only be used at high speeds when you don't need much power.

TOM: If you're driving at less than about 45 mph, and you're changing speeds a lot, or going up and down hills, you should put the transmission in regular Drive--or third gear--and leave it there.

RAY: The transmission's "job" is to get to the highest gear as quickly as possible. It does that in order to maximize efficiency. So even if you're just driving around town, the transmission will keep trying to get into overdrive. The problem is, as soon as it gets there, you'll step on the gas and make it down??shift to a lower gear.

TOM: In effect, the transmission will be shifting all the time--constantly "hunting" for the right gear. This puts some extra wear and tear on the transmission, which is one reason it should be avoided.

RAY: But the more important reason to avoid this sort of "hunting" is that, as you probably know, it tends to be very annoying.

TOM: And given your situation, Joe, you'd be well advised to keep annoyances to an absolute minimum.

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