[tongli]

I had my GG MDX for about a month and I love it. When I bought the car, the sales man told me I should use D5 for most of the driving. Same said on the manual. I never drove a manual transmission car before and all the cars I had before only had one D there. Now I have three choices D5/D4/D3 and am wondering if and how I can use all three. I had the impression that changing gear while driving mountain road will help braking and control, but not sure if it is right.

Any suggestion/experience is appreciated.

 

[DaleB]

Go by the manual to start. It gives you the basic purpose of each gear, and when to use it.
One main advantage of slipping down to D4, and even D3 is to save some wear on the brakes when descending a steep grade, and you want your speed reduced for safer handling, or when towing a load.
Of course the lowest gears are intended for SLOW driving, especially when pulling a heavy load, descending or ascending steeper than typical grades, poor road surfaces, etc.
Myself, I always keep my automatics out of the overdrive range in stop and go traffic, where the transmission tends to shift needlessly in and out of overdrive. To save some wear on the tranny. The higher engine revs tend to offer more cooling also.
You might do the same on a winding road where there are a lot of switchbacks, and you can never attain high enough speed to use the higher gear(s).
For just running down the avenue and jumping on the freeway, I just keep it in the highest gear.
I think the principles are the same for most all vehicles, the top two gears in the MDX are higher (overdrive) than most though.
Of course I am not covering all conditions like, uh.. well, racing (ill advised!!) where depending on the vehicle it is better to shift manually though the gears, or let the automatic do it's thing. The automatic in the MDX was not designed to be a 'sport shifter'.
How it gets used, is another story....

 

[tongli]

Thanks, DaleB. This answers my question. Sorry to see that your order was delayed to 5/11. But I am sure you will like your GG once you get it. I just posted a link to my GG website in Gallery section. In case you have not see it, Here it is

http://homepage.mac.com/tong_li/GG.html

This should help you out in waiting another extra week for your GG. It is beautiful, isn't it?

 

[DaleB]

Fantastic fotos! Yes, I am very anxious. Actually, that very vehicle may have been mine! I jumped off of Michael Andrew's list over a month ago. My original request was for a Base + Navi. I told him near the end I would consider going with a touring + navi. I think there was a communication breakdown. Oh well, no hard feelings, Michael was a gentleman as always, and I would not hesitate to recommend Hopkins Acura to anyone.

BTW, others on here can fill you in on grade-logic which from what I can tell is a feature of the MDX where you don't have to manually shift as often like when descending grades, etc.

 

[DaleB]

This should help you out in waiting another extra week for your GG. It is beautiful, isn't it?

I had not really considered the BSM that seriously. In fact ifeldman and I were just corresponding about that. But now I see it on yours it doesn't look bad at all. That's what makes GG such a great color, things blend in so well.

 

[roadrunner]

One main advantage of slipping down to D4, and even D3 is to save some wear on the brakes when descending a steep grade

I seem to remember hearing (it may have been on Car Talk) a discussion of this - and the conclusion was that it is a very questionable practice to put extra strain on a transmission (very expensive to repair) in order to save wear and tear on expendable and easily replaced brake pads. I have no expertise but I find this argument logical and compelling. Any of our more mechanical folks care to comment?
Meep Meep

 

[msu79gt82]

I believe the primary reason to use D4 ...

... vs. D5 is to prevent frequent unneccessary shifting in hilly terrain. If you are cruising at interstate speed in hilly country you may not want your transmission shifting frequently between D5 / D4 while going up and down the hills

 

[DaleB]

I seem to remember hearing (it may have been on Car Talk) a discussion of this - and the conclusion was that it is a very questionable practice to put extra strain on a transmission (very expensive to repair) in order to save wear and tear on expendable and easily replaced brake pads. I have no expertise but I find this argument logical and compelling. Any of our more mechanical folks care to comment?
Meep Meep

I think like anything else, you use it with some discretion. While moving sluggishly through traffic, I can't believe keeping the tranny in next lower gear is going to hurt anything. In fact, the tranny will be working less.
In other 'activities', I think it just depends on the conditions. I am not proprosing using it like a stick shift during everyday driving. Towing, and dealing with adverse road conditions are not everyday events for most of us.
And grade-logic appears to do a lot of that work for us. And for sure, I wouldn't downshift an automatic everytime I was starting to slow down to save the brakes. Besides, the tranny does that on it's own.
Brake work, while not that cheap these days, certainly pales compared with transmission repairs.

 

[renov8r]

Automatics freewheel when braking...

The downshift does not occur until you begin to accelerate from a lower gear. Torque is not braking against engine compression in normal operation.

Using any automatic tranny to "slow" a vehicle DEFIANTELY leads to high fluid pressures & heat -- and this WILL cause WEAR to the EXPENSIVE transmission!

The comments about keeping in D5 in all except UNUSUAL circumstances are accurate. The circumstances are consistent with what any automatic transmission was designed to do: help the engine spend the most time in an efficient rev range. The "hilly" terrain that would force a tranny to shift more than is optimium would have to include lots of changes in speed too. Just moving up a hill and then coasting down would not trigger shifting -- you need to motor up, coast down, motor back up to HIGHER speed, coast down, motor up REPEATEDLY.

Ditto for "stop-and-go in town traffic". The typical "in town" motoring will NOT see 5th gear (or even 4th). Unless by "stop & go" you mean "get to 45+ MPH, slow briefly, get back to 45 +MPH". Change 45+ to 35+ and THAT becomes the criteria for D3.

Of course, none of this holds for a "true sequential manual" 'auto' gearbox with an electro-mechanical clutch (ala BMW M3) BUT it would hold for even MOST "manually selectable automatics" because they have a TORQUE CONVERTER, and that is what allows freewheeling during braking/idle.