Join the Car Talk Community!

Discussion Rules

Welcome to the Car Talk Community!

Want to ask a question or join the discussion? Great! Join now.

Sign In Register

Should I downshift my automatic transmission?

I grew up with a stick shift, and always downshift on freeway offramps. My brakes just got replaced at 50K miles, which is good. But am I putting extra wear on my engine? I almost never make it rev over 3,600 rpm, drive it easy and get good mileage. I want it to last. Any opinions? Thanks.

Comments

  • edited February 2010
    I don't see how it can hurt anything. Look at it like this. If you were going down a steep incline and didn't want to overheat the brakes, what would you do? You'ld put the transmission into lower gear and get the assist of engine braking.

    Tester
  • edited February 2010
    You're not putting any extra strain on the engine, but you might be putting extra wear on the transmission.

    You're trying to save inexpensive brakes by using a very expensive transmission. I don't see the logic.

    I generally get 50K miles out of my brakes, and I never downshift (manual or automatic) as a means to slow down.

    Brakes are for slowing. Drive train is for going.

    I agree with downshifting on long downhill sections, to avoid too much speed, but I can't see doing it every day under normal driving conditions.

    It is, however, your car, so you can drive it as you see fit.
  • edited February 2010
    Why bother? It's not called an "AUTOMATIC" transmission for nothing. The only time you should need to downshift it manually is when descending a long grade.

    For that matter, why downshift a manual? Brakes are far cheaper than clutches and transmissions. I say that, and I can double de-clutch downshift with the best of 'em. Unless you're in a really tight situation where engine braking is needed to stop shorter, it's just not needed.
  • edited February 2010
    Don't. The transmission will downshift on its own when necessary thus you still benefit from the gear reduction. Also there's the possibility that you get on the throttle at the bottom of the ramp and forget to put the car back in forward drive first. Use your imagination on that one.

    Oh, no harm done to the engine as long as it's had a chance to warm up before putting that kind of load on it.
  • edited February 2010
    We live in a mountain area and dowshifting is highly recommended when you descend several thousand feet. The same is true when going up a mountain pass; at least take the car out of overdrive. On very steep passes we shift down to 2nd on a 4 speed automatic. It even says so in the owner's manual.
  • edited February 2010
    Go price the cost of new brake pads and then price the cost of a new transmission.

    OK now that you get the basic part right (leave it do its own thing) you can look at the exception. On lone downhill runs, you don't want to have the brakes do all the work. So only on long steep down grades downshift the auto to provide some braking.
  • edited February 2010
    I appreciate all the input. Yes, I have shifted to 2nd while slowing, and then after starting out (when the RPMs got high) said "OOPS, I forgot AGAIN!" and bumped it back to Drive. And I have noticed how smart the computer is (after light braking for several seconds on a downhill, it will disengage the overdrive by itself, with no input from me via the shifter or O/D button). So, unless descending a long downhill grade, I'll forgo any moves to lower gears, and let the computer decide.

    What about SHIFTING TO NEUTRAL while approaching a stop light that is red? It bugs me that long, gradual stops (like freeway offramps) that would be effortless in a "shifter car" require much more braking with an automatic transmission (especially as the speed gets lower). Shouldn't I shift to neutral approaching a dead stop from 40 mph, use the brakes to stop the car, and then (when it's green, either stopped or slowly moving forward) bump the shifter back into Drive?

    Again, input is welcome. Will shifting from Drive to Neutral at about 40 mph, stopping, and then (while at a stop), shifting to Drive also cause more wear and tear ('cmon, it's all computer controlled, right?) than just leaving it alone?

    As has been pointed out, brake pads are cheap compared to engines and transmissions. I want to do whatever makes the most sense in terms of maintenance costs for the long term, and good gas mileage. Thanks for all the input!

    Alan McCornack
  • edited February 2010
    If used sparingly in limited situations I don't see a problem with it. If it's chronic it might be a problem.
    While shifting it manually may come across as a smooth and barely noticeable operation, inside the transmission fluid pressure is being released and applied whenever you move the lever. This means clutches are going to be getting slammed around a bit so my vote is no unless necessary.
  • edited February 2010
    OK, I think the consensus is pretty clear. Like most of my friends, I think I'll just leave it in drive (unless I'm disengaging the overdrive for a hill where I need more power but don't want to "floor" the gas pedal). Thanks for all the input!

    Alan McCornack
This discussion has been closed.