During the past decade, most vehicle manufacturers have added an array of multi-speed automatic transmissions to their lineup to meet fuel economy requirements and increase vehicle performance. Certain manufacturers have outsourced transmission needs to other companies such as Aisin, Jatco or ZF while other vehicle manufacturers have developed transmission models in-house.
Mazda, for instance, over the years has utilized Jatco and Aisin for various transmission models as well as being involved with Ford in developing others. When Mazda decided to implement new technology affecting not only engines but transmissions as well, engineers started out with a clean sheet of paper and developed the FW6A-EL FWD six-speed automatic from scratch. The overall appearance and layout differs from all other six-speed transmission models to date. From an operational standpoint, though, the FW6A is somewhat in sync with other six-speed transmissions and Mazda had even adopted some of the component terminology such as how the clutch packs are referred to.
The FW6A contains five different clutch packs (two rotating clutches, three stationary brakes) and three planetary gear sets nested together similar to the GM 6T70. The pump assembly is direct drive and the transmission has a bottom pan instead of a side valve body cover that differs from the 6T70. Aside from diagnostic issues and parts availability, working on this new model transmission should not be too bad. From a disassembly standpoint, most components can be removed with the pan and valve body in place. The question becomes, which end to start from: the front or the back?
Bell housing:
Removal of the bell housing is fairly straightforward with few surprises. Before removing the housing, it would be a good idea to unbolt the auxiliary cooler to avoid damage, assuming that the cooler doesn’t require replacement. When it comes to bolts, don’t look for any involving the pump because there are none, due to the design. The first thing to note with the bell housing removed is that Mazda decided on using RTV instead of a gasket. In fact, the FW6A literally does not use any gaskets although a pan gasket is available for service.
The backside of the bell housing is fairly basic but does have an oil baffle that bolts to it and has a couple of flat areas for case O-rings. There are two pockets for the differential and pinion shaft bearing races and selective shims. In addition is the recessed bore for the pump compression seal (Figure 1).
Case (front end):
With the bell housing out of the way, several components are accessible (Figure 2). Items such as the differential and pinion shaft assembly will actually fall out, which is why the bell housing should be facing up during disassembly. Remove the pinion shaft lube tube at this time. The pump assembly bolts directly to the case, which is why the bolts are not visible externally. With the pump removed, the input shaft and rotating clutch assembly can also be pulled out easily, exposing the output gear. Shifter components are accessible as well.
The FW6A uses a traditional differential, pinion (secondary) shaft and main output gear (Figure 3A). There is one little issue with the output gear beyond removal of the big nut that retains the front (output) planet carrier. If an attempt is made to remove the gear, most likely the case bearing will be damaged due to the inner race separating from the bearing cage allowing the steel balls to fly out in every direction.
If the bearing is damaged, the case will have to be replaced because the outer race uses a non-accessible snap ring that holds the bearing assembly to the case bore, similar to a Toyota U660E. Unlike the U660E, Mazda does not currently offer a replacement bearing (Figure 3B). Mazda issued a TSB concerning a whining noise that may be due to the output gear bearing, in which case Mazda does recommend replacement of the entire transmission.
Pump assembly:
The design of the pump somewhat mimics an A4LD, in that the pump gears are actually situated within the stator support instead of the pump body (Figure 4). The pump cover is merely a flat plate that bolts to the stator support and contains the torque converter hub bushing and metal-clad seal. There is also a lip on the front side of the cover that is the pilot for the bell housing compression seal. The stator support contains four sealing rings for the rotating clutch assembly.
The pump gears must be installed facing the proper direction and both gears have a locating mark for identification. When installing the gears into the stator support, the ID marks must face downward, which will ensure that the drive flats of the inner gear and rounded edge of the outer gear are positioned correctly.
Rotating clutch assembly:
The input shaft splines directly to the rotating clutch drum, which contains two different clutch packs, the low clutch (large diameter plates) and the high clutch (small diameter). The drum assembly is fairly basic with one exception: The two main housings are welded together, which prevents removal of the low-clutch piston (Figure 5A). If the piston is defective, the entire drum assembly will have to be replaced; therefore, air-check the low clutch before disassembly. The input shaft is not held in place by a snap ring and can easily fall out of the drum.
Both the low and high clutch packs are pretty straightforward with only the low clutch having a cushion spring. As with other later-model transmissions, the FW6A uses segmented friction material for all clutch positions. The high clutch pack not only has a bonded rubber piston but also uses a bonded rubber retainer as well (Figure 5B). The high clutch hub rotates within the low clutch hub and both hubs extend rearwards into different planetary components. Thrust bearings separate the hubs and in fact are used throughout the transmission with no thrust washers to be found.
End cover components:
Much of the transmission components are accessible by removing the end cover. The end cover bolts to the case like many other transmission types and as with the bell housing uses RTV instead of a gasket (Figure 6A).
In addition to a couple of small O-rings that compress between the end cover and case, there is a long cooler tube that extends from the end cover, through the case and into the bell housing (Figure 6B). The tube, which is for cooler return, uses several different seals and must be assembled correctly or a big-time failure will occur.
Two of the three stationary brakes are contained within the end cover and the reduction planetary assembly is removed at the same time as the cover. The plate that bolts to the top of the end cover is actually a piston housing that is spring-loaded due to the clutch pack return spring. With the piston housing removed the reduction planet and clutch components are accessible.
2-6 stationary brake:
Mazda did decide to use some GM terminology when describing certain components such as the stationary brakes (clutch packs). The first clutch pack to be removed from the end cover is for 2nd and 6th gears and is responsible for holding the reduction planet carrier stationary. The apply piston is bonded rubber and the piston housing apply hole sets directly on top of a valve body passage with a flat seal in between. The piston return spring sets right on top of the piston without any snap ring (Figure 7). There are four frictions and four steels; however, the top steel is selective and will have a number stamped into it. Note the position of the steel plates during disassembly. The backing plate has raised bumps on one side that locate against the piston return springs.
3-5/reverse stationary brake:
The other stationary brake contained within the end cover also applies as the name indicates, just like the 6T70. The bonded piston sets in a cavity in the end cover and the piston return spring rests directly on top of the piston, as with the other clutch pack. There are three frictions and three steels used for the 3-5/rev clutch pack position. The backing plate also has locating bumps to mate with the return springs and must be rotated correctly (Figure 8). The piston apply hole in the cover is fed by a corresponding hole in the case, which also uses a flat seal. When applied, the clutch anchors the reduction internal gear to the end cover.
Low diode (OWC):
Each transmission manufacturer must determine whether a given transmission should have some kind of one-way clutch or not. Mazda chose to add a mechanical diode to the FW6A to be active in first gear. In addition to the component being a one-way clutch, it also acts as the backing plate for the low reverse clutch (Figure 9). As with the other backing plates there are also raised bumps on the teeth to support the open end of the L/R piston return springs. The diode is retained to the case with the largest snap ring in the unit.
Low/reverse stationary brake:
The third stationary clutch pack in the FW6A is for low/reverse and is positioned in the middle of the case making it the final friction element to be removed. With the low diode out of the way the frictions and steels can be removed and special attention should be paid to the positioning of the steels in order to help during reassembly (Figure 10). As with the other frictions in the unit the L/R frictions are segmented with a quantity of four in conjunction with four steels. The apply piston is also bonded and the return springs locate against it. The oil apply hole extends through the case to the valve body and when applied will hold the rear planetary stationary to the case as indicated.
Reduction planetary set:
The planetary gear set at the back of the transmission is referred to by Mazda as the reduction planetary. The planet set is removed along with the end cover but is not accessible without removing the 2-6 piston housing. The ring gear that is splined to the carrier is for the rear planetary set (Figure 11).
The planet carrier itself is splined to the 2-6 friction plates and when applied is held stationary. The reduction ring (internal) gear, which sets deeper into the end cover, is splined to the 3-5/reverse friction plates and is held stationary as well. The reduction sun gear is splined to the input shaft and looks to be installed upside down at first glance. Thrust bearings separate all components; however, a selective spacer is located between the planet carrier and sun gear thrust bearing. Ensure that the stack up is correct.
Installing the planet carrier into the end cover during reassembly can be a chore because the frictions and steels must be installed first with the carrier being rotated into position while engaging the friction teeth. A better option would be to stack the plates onto the carrier and, with the steels aligned, install the setup into the end cover. It’s a matter of choice.
Rear planetary set:
The middle planet set, which Mazda refers to as the rear planet, is what splines to the low diode and low/reverse friction plates. The unit becomes visible once the end cover assembly has been removed and will slide right out of the clutch assemblies. The ring gear, which is splined to the rear carrier, is for the front planet and has both narrow and wide teeth (Figure 12). The rear sun gear has a step at one end that must face forward and is splined to and driven by the low clutch hub. The planet is held stationary in first gear and reverse.
Front planetary set:
The front planet, as Mazda calls it, is actually the output planet carrier that splines to the output (drive) gear. The stub end of the carrier is threaded to accommodate the output gear locknut, which requires 250 lb.-ft. of torque (Figure 13). The front sun gear is bidirectional and also splines to the low clutch hub, just like the rear sun gear. Use caution when removing the planet carrier from the output gear to avoid possible damage to the support bearing in the case.
Bottom pan/valve body:
The bottom pan is a fairly traditional metal pan that utilizes RTV from the factory instead of a gasket. The upside is that there is no stand pipe for fluid level check as other newer transmission models have, since there is an actual dipstick at the side of the case (Figure 14). The all-plastic filter has a large and small outlet that fits up against two valve body ports, although the small outlet is merely a bypass.
Valve body:
The valve body on this transmission is a major chunk of aluminum and contains a lot of stuff to deal with. One noticeable exception from other transmission models relates to the electrical connector case seal. The hole in the case where the connector protrudes through is twice the diameter of the connector itself requiring a top-hat-looking seal (Figure 15A). In addition, where the seal contacts the connector, a hose clamp is actually used to keep it tight. On the connector side of the valve body are two RPM sensors, one for the rotating clutch and one for the output gear. To make matters worse, Mazda chose to have a mechatronic-design valve body that contains an internal TCM. Good luck with component interchangeability.
The bottom side of the valve body not only contains seven solenoids and related harness but also has two different pressure switches that Mazda refers to as A and B, which look similar to GM pressure switches (Figure 15B). As with GM, Mazda has already had some issues with those switches, therefore it may be prudent to consider replacement during a major repair.
The solenoid harness serves two different purposes with one being to connect all of the electrical items together, solenoids, pressure switches, TCM, etc. The other purpose is to retain the solenoid locating pins to the valve body (Figure 16). The metal tabs on the hold-down brackets contact the retaining pins, meaning that if the harness is removed in the vehicle, get ready to go fishing.
Transmission durability, diagnostic difficulties and parts availability will become apparent as time goes on, but from the wrenching standpoint it shouldn’t be too brutal.
September 2016 Issue
Volume 33, No. 9
- Mazda SkyActiv-Drive Six-Speed Automatic
