Other Articles - October/November - 2016

Ring Ring, RE5R05A Calling!

The RE5R05A was first introduced to the market in 2002 in the Infinity Q45. Several other vehicles used it in later years with some models such as the NV, still using this transmission for the 2016 production year. Since its inception, the transmission designer, JATCO has used rigid sealing rings produced with PEEK material in several locations within the transmission assembly depending upon model and year. As well, JATCO designed the Subaru 5 speed also referred to as the TG5C. This unit is based on the RE5R05A with the exception that all of the Subaru 5 speeds are all-wheel drive units with the typical final drive unit incorporated into the transmission.

The sealing rings used in the RE5R05A vary in design and material by model, as well as years within the model. This has led to confusion at repair facilities. Conversely, the rings used in the Subaru 5 speed, are consistent in style as originally designed. All sealing rings used in Subaru applications are made using PEEK material, and are designed with a scalloped inner diameter and a 3D joint (illustration A).

All RE5R05A’s use a scalloped, 3D joint ring made of PEEK material on the input shaft, from the factory. TransTec® engineers have worked with rebuilders and Freudenberg-NOK Fluid Power engineers to redesign a Teflon® ring with a step joint that not only performs better in the vehicle but also bench checks better ( illustration B).

Speaking of bench checks, whether hydraulic or air check a higher leak rate should be expected when testing most OE designed plastic style rings. The rings are originally designed to fit loose in the bore to ease the assembly process during transmission production. This fit helps to eliminate ring breakage caused by the ring hanging out from the ring lands, then catching on the bore during assembly of the components. The loose fit design will work even though the ring doesn’t hug the bore because at cold start of the vehicle, the transmission fluid is thick. This ensures only minimal leakage past the rings. After the transmission heats up, fluid begins to thin but the ring expands in size due to thermal expansion. This thermal expansion provides positive sealing to the bore reducing the leak rate even further. Unfortunately, this design doesn’t provide much confidence for the builder when bench checking the unit. When the OE ring is not available in the aftermarket, TransTec® engineers redesign it with a free-state diameter slightly larger than the bore, ensuring the ring will hold to the bore to produce a better bench check and also perform properly when installed in the vehicle.

The three rings on the reverse brake (center) support pro-vide fluid to the direct and hi-low/reverse clutch assemblies. These rings were originally manufactured in a few different designs. One design is the same as the input rings, made with the scalloped, 3D joint. The second design is a “T” design with a 3D joint (illustration C). According to recent OEM parts film, the center support ring with scalloped design has changed to the “T” design with one exception. The Subaru 5 speed still uses the original scalloped design. TransTec® offers only the “T” design for both the RE5R05A and the Subaru 5 speed. The “T” design has been shown to have less leakage than the scalloped design, especially when the ring land area of the support is showing wear. Of course, this design can’t make up for a support that should be replaced due to excessive wear.

Why are both the “T” and the scallop designs used for the sealing rings in the center support area? Sealing ring manufacturers are always looking for ways to improve the sealing abilities of the ring, as well as looking for ways to reduce wear. Many considerations go into ring design and material selection including fluid, temperature, rotational speeds, bore material, shaft material, surface finish & operating pressures. One design may work well when mating components are new and without wear, but not as well when wear becomes present. One design may be more forgiving than another design after wear of mating components. TransTec® technicians have learned that the center support in the RE5R05A has an issue with wear on the ring lands. After some customer interactions, discussion with Freudenberg-NOK Fluid Power engineers and testing, it was determined that the “T” design would be more forgiving of wear in this area. This prompted exclusive use of the “T” design for the center support in TransTec® kits.

The next set of rings is used on the mid sun gear shaft. Depending on the model of car, the set may contain four of the same rings, or two sets of two rings each. In units using the same four rings, the rings are made of PEEK material and designed with the scalloped 3D joint. In units using two sets with different designs, all four rings are made of PEEK, two rings are designed with the scalloped 3D joint and are located toward the front set of lands. The second set is located towards the rear and the rings are designed with a 3D joint but are not scalloped (illustration D). TransTec® kits contain PEEK, non-scalloped 3D joint rings, because the design is much more forgiving for wear issues.

The last set of rings in the RE5R05A is for the output shaft. The designer chose to use rings made of Teflon® and PEEK, depending on the vehicle model and year. The PEEK rings are made with the scalloped 3D design, and the Teflon® rings are made with a butt cut design. (illustration E). TransTec® kits contain the Teflon® butt cut rings because they bench check better and perform well during normal operating conditions.

Not All Rings Are Created Equal

Not only is design of the sealing ring critical, manufacturing of the ring will also determine quality and ensure proper sealing within the application. Rings produced with low quality tools can display injector pin marks on one side of the ring. These marks are created by pins used to remove the ring from the tool. The injector pins displace material, creating a build-up of excess material or high spots. The displaced, or excess material can be high enough to create an insufficient contact with the ring land. Any area of the ring not making contact with the ring land is a leak path for oil. Conversely, rings produced with high quality tools will ensure a flat surface on the side of the ring because a sleeve, rather than ejector pins is used to eject the ring from the tool. The sleeve evenly distributes pressure across the surface of the ring avoiding material displacement. On two-ring oil circuits, a builder can install the side with the injector pin marks toward the oil feed, which in turn will allow the smooth non-injector pin side to push tight against the ring land from the apply pressure, thus creating a sufficient seal. (The side of each ring that has the injector marks should face each other.) If there are more than two rings because there are multiple oil circuits being serviced, the technician should understand each circuit and install the rings with the injector marks in a circuit that has the least risk. Freudenberg-NOK strives to ensure that all sealing rings are manufactured with quality tooling and production processes, and that materials and designs meet the requirements of the transmission.