IMHO there really should be no reason to manually override Automatic selection of the next gear in D or D3 programmed shift logic under normal driving conditions, but Honda 5AT design flaws dictate otherwise. Notice there are 2 auto gear sequence modes, D and D3, one of these should be used in stop start traffic or when the vehicle is regularly driven at even "slightly varying speeds" below 40mph for any period of time.
The Accord 5AT has often been used as a replacement transmission in a matching TL with paddle shift. It works flawlessly, changes exactly the same and suffers from exactly the same build and failure modes as the TL 5AT because it is the same transmission, with the possible exception of a gear ratio. However I find paddle shifts in an Automatic mostly a waste of time and more a gimmick - but that's just me I guess.
For the most part, a 5AT in good condition and correctly maintained (pressure switches, filter change and connector cleaning) and *good synthetic fluid* will shift really well. The 5AT in my accord shifts perfectly, there are no harsh shifts, no harsh downshifts under grade logic, all shifts are crisp, quick and smooth, it's always shifts up or down to the gear I would normally be in if I were driving a manual and - Shock! Horror! - I'm running with moderately reduced FM (friction modifier) and a fully synthetic fluid which is not (trying to contain hysterical laughter as I write the next 3 words) *Honda precision crafted* Z1 or DW-1.
BTW: IMHO Z1 is dinosaur oil, DW-1 appears to be simillar with slightly less FM, lower viscosity and from the base stock, not a true synthetic fluid.
Now of course you will increase clutch pack wear if you foolishly / needlessly shift up and down (abuse) this transmission. On the other hand you can decrease wear and "reduce needless auto shifting" with the CORRECT use of the - I'd like to automatically shift into gear X - Manual "gear select" override leaver.
In the strict sense you don't *manually shift* an auto transmission, the shift is always automatically controlled by the transmission and TCU. You can manually hold 1st and 2nd gear, you can manually ask for a gear and if it's within the design parameters of the TCU and ECU for that gear and conditions then the transmission will *automatically shift* into the gear for you with the same sequence of clutch pack overlap, timing and control as it would under straight Auto mode - D3 or D.
IMHO there are only a few conditions where this 5AT needs some manual input.
If you need to *very quickly* accelerate from moderate speeds in an auto, you normally press the accelerator to somewhere near WOT to get the trans to *quickly shift down* - this is referred to as a *forced downshift* or kickdown shift.
Do that in this 5AT you may now have a real problem! Depending on your speed you may be in 4th, and allowing the transmission to do this shift automatically will cause a forced downshift into either 3rd or 2nd. If the trans shifts into 2nd it will expose a design flaw in the 5AT that causes accelerated wear in the 3rd gear clutch pack. However it doesn't end there, it takes some time to fully complete a shift due to flawed slush box clutch overlap logic and extremely high FM fluid. Quite often as the shift is in progress you back off the throttle slightly because 2nd gear acceleration at near WOT is too great for the conditions, doing so will *initiate* an auto shift to 3rd and now rip into the 3rd gear clutch pack "even more" as another design flaw causes 3rd gear clutch packs to drag at higher pressure before the shift from 2nd has completed (2nd gear clutch pressure is dropping but it's still locked).
Telling the transmission that you want to automatically shift into 3rd - by not getting hard on the accelerator and selecting D3 - will almost guarantee that the TCU won't perform an automatic (forced) shift into 2nd on a "quick" kickdown. Of course if you have time you can control a forced downshift under throttle by not getting too hard on the accelerator, this will usually result in a shift into 3rd. But if you need to shift hard without a delay then select D3 as you accelerate.
This scenario is even more likely in stop start traffic in *D*. Any time you back off the accelerator at slow speeds (when the trans is hot) it can shift into 4th, any quick acceleration as traffic speeds up will likely cause a shift into 2nd.
When driving below 40mph in 4th (and 5th) the Torque convertor (TC) has a tendency to slightly hunt or rapidity go into partial lock/unlock states due to TCC logic being at the limit of TC programmed control, this is a great way to overheat and burn the TC. If the TC is hot you could have an even greater problem at idle in gear (stop start traffic) as there is very little oil flow through the TC and cooler circuit in the 5AT under this condition and TC-cooler flow is compromised by yet another design flaw, it can literally fry the TC.
You should be doing everything you can to reduce repeatedly shifting 3-2-3-4-3-2-3 when driving in stop start traffic, if you don't you will have one overworked HOT 3rd gear clutch pack and *bulk fluid temperature may not rise much at all* so a temp gauge or external cooler may not help in this condition.
Honda indentified increased clutch pack wear and very high spot fluid temperature in a number of areas when investigating 5AT failures, one was the 3rd gear clutch pack with repeating 2nd to 3rd shifts, this could be encountered in very slow stop-start traffic. It's amazing how often the transmission shifts between 3rd, 2nd and 1st, and especially 3-2-3 shifting. if you are in "D" then add 3-4-3 on top of 3-2-3. In normal slow traffic I am always in D3.
Now you could just lock the transmission in 2nd and avoid any 2-3 shift until traffic started to move a little freely. However if you come to a stop you really need to shift into 1st because the TC will be creating quite a bit of heat with reparative acceleration from a stop in 2nd (TC stall speed). There's no clutch engagement overlap when shifting from 1st into 2nd (no clutch pack dragging), so 2nd gear clutch pack should be under little duress, doing this will eliminate wear and heat in the 3rd clutch pack under this harsh driving condition.
Now of course, looking at forum responses of late, I'm sure most of you are also experts at watching the tachometer and you always know what gear your auto is in and automatically compensate, so please ignore the following. For those like me who spend more time watching what is happening outside the vehicle, like drivers staring at the tachometer and idiot drivers around me in heavy traffic or freeway merging lanes, you may need a way to counter these scenarios.
Below 40mph I shift to D3, usually waiting until the trans has dropped to 3rd or in 4th and about to do so, this does not harm the clutch packs, takes care of TQ logic and stops needless shifts into 4th and 5th and needless 4-3 / 3-4 shifts.
Freeway merging depends on looking ahead traffic conditions, as I'm coming from a slower speed I'm usually in D3 and usually hold D3 until I get a look at merging conditions then shift to D when required. Again shifting into D3 "early" (before having to get on the accelerator) will guarantee that the TCU won't perform an automatic (forced) 4-2 shift with Auto kick-down.
Do you really thinks it's easier on the transmission, clutch packs, engine and gear train to floor the accelerator (Auto kick-down with near WOT) instead of shifting into D3 early, then shifting to D when RPM, speed or conditions dictate? Seriously?
I don't believe it's good practice to use an auto for engine breaking over and above that already controlled by grade logic - You don't want to be needlessly working clutch packs by shifting to lower gears *at speed* just to slow the vehicle. However on steep slow mountain descents, selecting D3 or 2nd (after you have braked and slowed) may be advisable but only if you stay in that gear for a period of time and are still using the brakes, under these condition there is no harm to the clutch packs, the only real load is on the drive-train and TC. But you will have some of that in any case. This is not the same us power downshifting to slow a vehicle, NOT a good idea!
Preformed a quick 3 litre change of trans fluid yesterday after another 24,000 Km (it's not a lot, I know!) including quite a bit of mountain driving. Fluid was like new, not a single metallic "hair or fuzz" on the drain bolt magnet, only a "tiny" smear of black metallic paste. I always inspect the transmission filter and pour old fluid through a white coffee filter, both were clean, the white coffee filter was spotless except for a clean red stain, not a speck of darkness or wear material.
If this style of driving is damaging the transmission you would see it here - unless you believe that Honda transmission fairies hide it somewhere and it only comes out to play if you use "precision crafted" Z1. You can't wear clutch packs, TC or chew up gears and have nothing show up in the fluid, filter or magnetic drain bolt in this 5AT. This is the cleanest change I have had.