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Automatic Transmission

Honda 6-Speed Automatics: How little certain things change

In an age of vehicles with seven-, eight- and even nine-speed automatics, Honda is the one constant in an ever-changing world. Transmission manufacturers have achieved the goal of extreme-ratio transmissions (a 10-speed is on the horizon), without adding iron, due to the advent of Lepelletier planets and advanced computerization. Honda, however, has stuck with its traditional architecture.

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Technically Speaking

  • Author: Mike Riley, Technical Editor
  • Subject Matter: Automatic transmission
  • Unit: Honda six-speeds
  • Vehicle Applications: Honda, Acura
  • Issue: Design changes

In an age of vehicles with seven-, eight- and even nine-speed automatics, Honda is the one constant in an ever-changing world. Transmission manufacturers have achieved the goal of extreme-ratio transmissions (a 10-speed is on the horizon), without adding iron, due to the advent of Lepelletier planets and advanced computerization. Honda, however, has stuck with its traditional architecture.

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Honda first released the Hondamatic two-speed back in the mid-’70s, and it was a departure from a regular automatic in that gearing was standard-transmission in nature, not a planetary design. There was even a synchronizer assembly for forward and reverse. How did the two-speed become a three-speed and then a four-speed? By adding more gears (iron).

Back then, even planetary-type transmission ratios were added by increasing the part count (e.g., 200 to 200-4R, TF6 to A500 etc.). Computers started to change all that in the mid-’90s by cycling components differently (e.g., 4R55E to 5R55E). Today, computers and planetary design can provide engineers with the ability to get more with less.

The Honda four-speed was launched in 1983 and had a seven-year run before getting any substantial changes. Beginning in 1990, the four-speed went from a two-shaft design to a three-shaft design, primarily to provide engine braking. By the mid-’90s, increased computer controls changed the approach somewhat, but the gearing remained the same.

The three-shaft design enabled Honda to launch a five-speed transmission in Y2K (2000), again by adding more gears and clutch packs as well as electrical stuff. A three-shaft design consists of the mainshaft, secondary shaft and countershaft.

In 2003, Honda made another quantum leap by releasing a four-shaft, five-speed transmission. No more speeds, just a different arrangement from the three-shaft. Was the goal to add more weight? Probably not.

Throughout the 2000s, other car companies participated in “the battle of the gears,” but not Honda. Four- and five-speeds with the occasional CVT were it. Then, in 2010, Honda unleashed a six-speed automatic, although on a limited basis.

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The 2010 Acura MDX and ZDX and certain 2011 Odysseys were equipped with the six-speed. The Accord and other models have also started to get a six-speed transmission. There will be more.

Externally, unlike other Honda units, there is no mistaking a six-speed (Figure 1). There are a lot of do-dads that are visible. Model variations also exist. For instance, not only is an AWD MDX different from a 2WD Odyssey, due to a transfer case, but the bellhousing-to-case configuration is different as well.

The first component to focus on would be the solenoid block (Figure 2). Previous four- and five-speed single and dual linear solenoid sets can only stand in awe of this monster. Not only are there seven solenoids attached, but there are also several pressure switches to boot. In all, a six-speed has eight solenoids and six pressure switches scattered around. There are also input/output speed sensors to deal with. For some reason, the SSC solenoid got mounted to the case instead of the solenoid block. It must have been naughty. There are eleven tubes with screens that connect the solenoid body to the valve body, all of which require O-rings. The solenoid body is not cheap to buy either.

Once the solenoid body and case half are out of the way, the guts of the unit are exposed. The Honda six-speed automatic is basically a four-shaft transmission. There is an additional idler gear, beyond the reverse idler, which drives the secondary shaft. On top of the four shafts with a ton of gears, including a one-way clutch, are – guess what – six clutch packs. Six speeds, six sets of clutches; how simple.

Disassembly and reassembly may be somewhat of a chore and should follow a uniform procedure. As with most Hondas, pay attention to the shaft nuts for left- or right-hand thread direction. Even the shaft-nut washers are not normal. Once the nuts are removed, certain bearings and gears will need to be taken off the shafts by using a bearing puller. Use caution not to break any gears.

The mainshaft (input) contains the third and sixth clutch-pack assembly, which looks like a normal fourth/fifth drum on a five-speed (Figure 3). Gearing and clutch-pack design and quantity are model dependent as well as having the normal number of Honda thrust and caged bearings. Note how the mainshaft components come apart for proper reassembly. Sixth gear also doubles as an idler gear while the transmission is in fourth.

The secondary shaft is comparable to 1990-up four-speed, three-shaft setups, except for a little more stuff on the six-speeds. The common clutch drum contains the second and fifth clutch-pack assemblies. The second clutch is toward the back and the fifth clutch is toward the front. The additional clutch-pack assembly on the secondary shaft is for first gear (Figure 4). The additional fixed gear is what drives the secondary shaft off the idler gear and mainshaft. Use caution to ensure that bearings, O-rings and sealing rings are correct and are not damaged during reassembly, just like with the mainshaft.

What separates the Honda six-speed from most five-speeds is the third-shaft assembly. The third shaft contains the fourth-clutch drum and related gears. Another departure from a four-shaft five-speed is that the forward/reverse selector components were moved to the third shaft from the countershaft (Figure 5). In fourth gear, the third-shaft sixth gear drives the countershaft via the mainshaft sixth gear (idler). The reverse drive gear is also part of the third-shaft assembly.

The last shaft on the menu is what all Honda trannies have: the countershaft. The Honda six-speed countershaft actually has fewer components than those of other Honda units. There is a left-handed 12mm allen end plug that retains the bearing and gears. The low sprag is also positioned onto the countershaft between park and first gear. Note the rotation before disassembly (Figure 6).

Valve-body design is fairly comparable to that of other Hondas, which means different chunks of bodies. The Honda six-speeds have several accumulator pistons, so make sure to mark the springs. There are also air bleeds that must be open.

Last, the torque converter uses a multiple-disc captive clutch like Mercedes or ZF. Time will tell whether they work any better. Lockup can apply in all forward gears.

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Computer controls and electronics aside, doing the six-speed should not be much different from a five-speed. Just count the gears.

Thanks to TransTec for providing the transmission.

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