Fun With Transmissions - March - 2018

The FW6A-EL: Mazda Does It In-House and My Daily Driver

The new Mazda FWD 6-speed comes in the following vehicles:

  • 2012–present — Mazda 2.0L–2.5L
  • 2014–present — Mazda 6 2.5L
  • 2013 — Mazda CX-5 2.0L–2.5L

In this edition of Fun with Transmissions, we’ll check out the in-house designed-and-built Mazda FW6A-EL.

The newly developed SKYACTIV-DRIVE automatic transaxle with cable operation, six forward gears, one reverse gear, and internal TCM (Transaxle Control Module) has been introduced. SKYACTIV-DRIVE combines all the advantages of conventional automatic transmissions, continuously variable transmissions, and dual-clutch transmissions.

A dramatically widened lockup range improves torque transfer efficiency and provides a direct driving feel similar to a manual transmission while achieving a 4.7% improvement in fuel economy compared to the current transmission.

The SKYACTIV-DRIVE automatic transaxle comes in two basic variants. Differences are in gear ratios and the number of friction plates based on a gas or diesel engine.

The Converter

First, if you check out the clutch apply chart (figure 1 — no bands in this unit) you see the torque converter is applied in all forward ranges and engages at about 7 mph.

Many OEMs are moving toward the clutch-pack style torque converter clutch and Mazda is no exception. This arrangement has a couple advantages to the traditional, single-plate converter clutch. The most obvious is more clutches! More friction area equals more durability.

It’s also necessary for the torque converter to be equipped with an enhanced damper mechanism to prevent shift shock due to torque converter clutch engagement at low speed. As a result, the torque converter is downsized for the space for a newly designed multi‐disc torque converter clutch and contributes to a downsized transmission and reduced weight.

The damper spring is designed to suppress noise vibration harshness (NVH) effectively. Two springs are used in combination: an inner spring and an outer spring. They’re different in diameter, winding pitch, and wire thickness (figure 2).

Mazda hit the mark with this design. The only time I’ve experienced any type of vibration is on a very light throttle, tip-in acceleration between 15 to 35 MPH (25 to 55 km/h).

What’s in There?

While basic converter operation is outside the scope of this article, there are many great articles and videos on the web you can watch to get a sense of how the torque converter functions.

The converter clutch consists of four, single-sided friction plates. Two plates have internal teeth and two plates have external teeth. This is all contained in the drum, which is part of the cover held in by a pressure plate and retaining snap ring (figure 3).

Just like any other driving clutch in the transmission, it has an apply piston and piston seals (figures 4A and 4B).

The Controls

The input and output devices are connected by the lower harness, located in the transmission or integrated in the TCM. These input and output devices and their connectors aren’t accessible from outside the transmission case. This design and arrangement reduces the wiring and enhances reliability (figure 5). This unit has seven solenoids: One on/off solenoid and six PWM solenoids used to control clutch apply, line pressure, and TCC apply (figures 6 and 7).

As with most electronically controlled transmissions, there’s one solenoid for each apply component. The one exception is the low/reverse/ high clutch solenoid. This solenoid does double duty, depending on the status of the on/off solenoid.

The valve body also has four pressure switches (figure 8). These pressure switches allow the computer to verify that the action — clutch on or clutch off that was commanded by the computer — actually happened.

If you haven’t seen them yet, you can be sure the FW6A-EL will be headed to your shop very soon. Look for a rebuild article in part 2 of our FW6A-EL series. We’ll cover some interesting points of the rebuild procedure, including some special tools that are a must-have when rebuilding this unit.

As always, the more you know, the more fun with transmissions you have!