Honda/Acura Automatic Transmission Design - Unique?

daysailerdaysailer Member Posts: 720
edited March 2014 in Honda
As I've come to grips with the idea that, to please my wife, our next car will have an auto' transmission, I've looked closer at a technology in which I've previously had no interest. I've learned that Honda's automatic design departs from most everything else on the planet (but then, they've never been shy about different technology). My info on Honda transmissions comes primarily from old, Accord and Acura Legend shop manuals but I've found nothing to suggest a radical departure later. Please correct me if you know differently. Are there any other manufacturers that employ a similar automatic design?

The following comparison ignores the torque converter since it is common to all automatics. While most (all?) other automatic (not CVT) transmissions use planetary gear-sets, Honda has used a mainshaft/countershaft arrangement of spur gears, not unlike a manual transmission. Advantages of planetary gear designs for automatics include constant-mesh gears and that multiple ratios, including reverse, can be derived from a single planetary gear-set. They have the disadvantage of being larger and more complex than paired spur gears and not as flexible in configuration, typically resulting in designs with a single shaft-axis that is not ideal for front wheel drive packaging. Consequently, automatic transmissions are usually large and heavy in comparison to manuals even without considering the torque converter and in spite of the fact that they usually have fewer ratios.

Honda design differs from a manual transmission in that the mainshaft gears do not form a single "cluster" gear but instead rotate independently on the mainshaft and are linked to it (or to other gears) as needed by individual clutches. In this arrangement the gears remain constant mesh (reverse is a special case) and unlike typical automatic transmissions, there may be only one pair of gears per transmission ratio (planetary gear-sets may be used in series in typical designs, reducing efficiency). Unlike a typical automatic where reverse is accomplished by stopping rotation of the planet carrier in one planetary gear-set, Honda uses a manual-like shift fork and collar to engage a separate reverse gear (does this relate to the metallic sound when engaging/disengaging reverse that some people comment (complain?) about?). Brake bands as used in planetary gear designs are not needed, but the number of clutches may be greater. This arrangement results in a more compact (and presumably lighter) automatic transmission, although it is still larger than a manual to accommodate the clutches (one per forward gear ratio) and control hydraulics.

An apparent challenge posed by the Honda design regards the clutches. Since the clutches cannot be larger in radius than the distance between shafts, they are necessarily smaller than in typical planetary designs where the clutches may be nearly the full diameter of the transmission (although perhaps with a narrower annulus). This means that a given torque must be handled by a smaller diameter clutch, which suggests higher operating pressure, greater component (and lubricant) stress and interesting control challenges. I'm not surprised that Honda ATF is "special".

I don't know whether Honda's design is inherently better or worse, but cars with this design have been in service for decades and Honda's reputation for quality has remained among the top in the industry. OTOH, in perusing the Internet, I have encountered references to Honda/Acura V6 transmission failures. Has engine power increased to the point that it exceeds some inherent design limitation? Are the transmission failures related to Honda's design or are they a QA issue? Was there a design change that caused a problem? OR, is the "problem" merely an artifact of an Internet that gives voice to a few who have experienced anomalous failures? How does one know?

I am a long-term Honda/Acura fan and owner (at least one has been in my "fleet" since '84), and I am now in the market for a new car, unfortunately with the dreaded "slush box" (although Honda's seem tighter than many). The Internet is a great place for information but it can be difficult to determine the acuracy and significance of what you find and those with complaints may be the most vocal so I hesitate to draw conclusions from forum discussions. Who has THE answer??


  • anselmo1anselmo1 Member Posts: 163
    The 6th Generation V-6 Honda Accord automatic transmission has had its share of failures. Honda salesmen do not want to admit to the ongoing problem so I personally suggest that anyone buying an Accord V-6 buy the Honda Care extended warranty.
  • lancerfixerlancerfixer Member Posts: 1,284
    You've gone way farther in your research than 99.9999% of drivers out there. I think if you end up with a Honda and an automatic, you'll be disappointed after having owned manual-equiped Hondas for so long. Honda engines just "feel" right with a manual tranny attached to them. I had entertained, a while back, the notion of getting a new family sedan to replace my '94 Accord (5 speed, of course.) I tested many, many cars, both manual and automatic (usually because there was no manual-equipped car on the lot) and thought that cars like the Maxima, Passat, and Camry felt a little better with autos than did the Accord. (Of course, had I bought one of those cars, it'd have had a 5-speed.) Interesting, though, reading your comments on the Honda automatics; it doesn't surprise me at all, knowing Honda's history, that they be setup like manuals.
  • spokanespokane Member Posts: 514
    I don't believe you will find THE answer, daysailer. Your assessment of the transmission design, and comparison with the conventional planetary automatics, is thorough and accurate. I understand that the Saturn automatics are similar to the Honda design but I don't know of any others. As you would expect, the Honda shifts are historically more harsh than those of a planetary drive system. The Civic transmission was updated for 1996 but the mechanical power-transmission details changed very little. The significant change at that time was the addition of speed sensors on each of the two transmission shafts. Their signals are used by the PCM to achieve soother shifts - involving brief fuel injection and/or timing changes to facilitate the shift quality improvement. Honda called this feature "grade logic" and it does minimize gear "hunting" on upgrades and provides some engine braking on certain types of downgrade. Those were the features that Honda touted but I thought the most significant change to be the shift quality improvement. Sorry I can't provide specifics on the Accord. It's my impression that the reliability of the Civic auto transmission is generally quite good even though the torque capacity of the clutches, as you point out, would appear to be questionable. Based on reliability over the course of a great many miles, I would not hesitate to depend on a Civic automatic ... but that doesn't mean I would choose it over Honda's excellent standard transmission. Sorry I can't offer any information of the recent Accord V6 transmission controversy.
  • barnonebarnone Member Posts: 118
    upon arriving at a stop light (turned red),
    is it advisable to put the gear in Neutral while
    in idle, then in Drive when light is green?

    i'm just concerned about wear and tear on the
    auto tranny.
    i know that for manual trannys, your pressure
    plate would have a reduced life if you were a
    clutch driver.

    kinda stupid question but i have been driving
    manuals for over 10 years and it's my 1st time
    to own an automatic tranny vehicle. i'm also
    used to the fact that when a manual stalls, you
    can use the "push n throttle" method to start
    the car (n/a on autos)
  • andre1969andre1969 Member Posts: 25,539
    ...I don't know about shifting the tranny into neutral at a traffic light. However, I HAVE heard that if you're at a traffic light on an uphill grade, and just let the engine idling hold the car still, as opposed to keeping your foot on the brake, that is supposed to be bad for it.

    Only time I've ever shifted into neutral is when I'm slowing down and the car feels like it's about to stall out. I'll shift into neutral and rev the engine a bit to keep it from stalling.

    The best way to make an automatic transmission last, though, is to make sure it's maintained properly, and when it's serviced that they put the correct fluid in. Even on cars where they have 50K, 100K, or even "tranny fluid for life", the stuff still has to be checked. And if it ever looks sooty, discolored, or smells burnt, it needs to be changed.
  • barnonebarnone Member Posts: 118
    thanks for the info!
  • 79377937 Member Posts: 390
    barnone, I also thought at one time that it would be a good idea to shift the auto transmission into neutral at a traffic light. But then you have to have a good memory! It's quite easy to forget what you have done. Mine was in neutral when the light turned green. I gunned the engine and nothing happened. So I moved the shifter into drive and was rewarded with mighty lurch forward and a lot of complaining noises from the transmission. Seems as though the engine was still at high speed when I slammed it into drive.

    Just do what andre1969 says and your transmission will last.
  • barnonebarnone Member Posts: 118
  • 79377937 Member Posts: 390
    Yeah, double DOH!! We aren't all geniuses. I know I'm stoopid. However, somebody more stoopid than me might get the idea and not do what I did.
  • barnonebarnone Member Posts: 118
    i'm not saying you're stupid. i was glad to
    read your post so i can learn from it =)
  • alcanalcan Member Posts: 2,550
    Saturn uses a parallel shaft automatic transaxle design similar to the Honda/Acura.

    Barnone: wear occurs in auto trans clutches and bands as they're applying. Shifting to neutral then drive at every traffic light will reduce their service life.
  • timadamstimadams Member Posts: 294
    Well, I know it's only anectodal, but I have a V6 Accord with auto tranny and have had no problems through 55,000 miles. Yeah, I know it's not 155,000 miles so I'll have to wait and see. But I also didn't have the problems at 2000 miles some complain about. I'm not saying there are no problems with any Honda V6 trannies, but keep in mind that it may not be as widespread as it appears on Edmunds.

    My opinion on my Honda AT: I love the grade-logic. I can't recall it ever hunting back and forth for the right gear; it always seems to be in the correct gear given the speed, incline and throttle position. I also like the fact that you get some engine braking when you take your foot off of the throttle, just like in a manual transmission car. I never knew that it was due to the somewhat unique design until I read the first post in this thread - thanks daysailer!

    After driving my Honda, I particularly notice in other cars that they remain at the same speed after I take my foot off the go pedal, and I have to use the brakes a lot more.

    I also like the "abrupt" shifts in my Honda, although I realize a lot of people don't, particularly those used to GM and Toyota automatic cars. The shifting seems hard to some people.

    I would have loved to get a stick shift with Honda's great V6 engine, but they don't offer that. I certainly hope they do with the next generation Accord. Otherwise, I will probably look at the competition that does.
  • barnonebarnone Member Posts: 118
    have you done a fluid change on your honda tranny?
    have you used additives of some sort?
  • chikoochikoo Member Posts: 3,008
    actually, I think it would be easier if somebody made an automatic out of a manual transmission. Just let the computer shift the gears for you by the use of solenoids and the like.

    what say?
  • timadamstimadams Member Posts: 294
    I did a transmission fluid change at 30,000 miles and will do again at 60,000 miles. Haven't used any additives at all.

    Chickoo: the type of transmission you describe is showing up on some high-dollar sports cars like Ferrari, Porsche (and BMW?). These are take-offs on the transmissions used on Formula 1 race cars. The driver uses little paddles to upshift and downshift, or you can have the car's computer do it for you automatically. But they differ from an automatic transmission because there is a clutch and manual gearbox. The paddle (or computer) actuates the clutch and gear changer to upshift or downshift, only much much faster than you or I can do with a clutch pedal and stick shift.

    I don't know how quick (or if) this type of shifting system will work its way down to cheaper cars. It's expensive as heck now.
  • chikoochikoo Member Posts: 3,008

    I would love to have that tranny come down to affordable cars.....will bring back th thrill of driving a car w/o getting laborious.....and maintenance would also be darned easy.
  • bburton1bburton1 Member Posts: 395
    Use only honda atf and do not use any additive/snake oil. The manual says to change at 90K on my 97 I4-however changing at 30K is a good idea. Make certain to get it hot before draining the tranny. You will need a funnel with a long hose attached to it-cheap. Be careful when taking off the drain plug from the tranny-you should drive it at least 30 miles to get it good and hot and it is really hot-will burn you to a crisp so be careful.
This discussion has been closed.