Patent Publication Number: US-2022228660-A1

Title: Transmission input housing forward piston sleeve

Description:
CROSS-REFERENCE TO RELATED APPLICATION DATA 
     This application claims the benefit of and priority to Provisional U.S. Patent Application Ser. No. 63/138,122 filed Jan. 15, 2021, titled TRANSMISSION INPUT HOUSING FORWARD PISTON SLEEVE, the disclosure of which is incorporated herein in its entirety. 
    
    
     BACKGROUND 
     The following description relates generally to a transmission input housing forward piston sleeve to increase the strength of the transmission input housing at the input shaft to housing spline interface. 
     The General Motors 4L60 series (4L60, 4L60E, 4L65E) and 4L70E automatic transmissions have an input housing that is an aluminum casting. The input housing accepts an input shaft with a press fit splined connection. The input housing contains a number of pistons that apply clutch packs to transmit torque to gearsets within the transmission. 
     Pistons within the input housing are engaged using fluid pressure to apply or engage the clutch packs. The pistons have inner and outer seals (diametrically inner and outer) to hold fluid pressure. The seals slide on smooth surfaces at locations along diameters of the housing and along the inner diameters of mating components in a direction parallel to the axis of the input housing. The clutch packs all have loose fitting splined connections with the input housing. These components, e.g., pistons, clutch packs, seals, are all nested together inside the input housing with minimal extra space. 
     Referring to  FIGS. 1A-1C , there is shown an original equipment (OE) 4L60 transmission input section  10  and input shaft  12 . The input section  10  transmits torque from the shaft  12  to any of a number of clutch packs in the input housing  14  and the transmission depending on gear selection. Fluid pressure is exerted on pistons to apply (engage) the clutch packs. Among these pistons are the forward piston  16  and the overrun piston  18  which engage the forward clutch  20  and overrun clutch  22 . The forward piston  16  is captured in the forward piston housing  24  and has an inner fluid seal against the input housing, and an outer fluid seal against the forward piston housing. The overrun piston  18  likewise has an inner fluid seal against the input housing  14  and an outer fluid seal against the forward piston  16 . 
     The forward piston housing  24  has an O-ring fluid seal against the input housing  14  on the inner diameter (inner seal). The forward piston  16  and overrun piston  18  are both able to move along the axis of the input housing  14  to enable clutch pack apply of the forward and overrun clutches  20 ,  22 . 
     These transmissions are often used for high performance applications. As such they may transmit more torque than originally designed to accommodate. In these high performance applications failures have been found to occur. One failure location is at the interface of the input shaft and input housing at the axial location of the overrun piston, as indicated at  34 . Extreme torque input will cause the spline to fail on the input housing. This failure mode was addressed by use of a steel sleeve pressed onto the input housing in the overrun piston area to increase the spline burst strength. Other components and kits have been developed in the aftermarket to increase the torque capacity of these transmissions. For example, components and kits for the input housing have been developed. Subsequently the 4L60 family of transmission has been used for even higher torque levels, which has led to the input housing failing at the next largest diameter near the splined connection in the forward piston area. It has been found that the 4L60E transmission input housings that utilize an overrun sleeve upgrade fail at the axial location of the forward piston diameter. This is due to the stresses imparted by the input shaft torque through the splined connection in that the torque levels are increasingly higher in high performance application, which torque levels are well in excess of the original OE design specifications for the input housing. 
     Referring to  FIGS. 2A-2C , there is shown one prior aftermarket kit and components that include a steel overrun sleeve  50  installed onto the input housing  14  with an interference fit to increase the housing  14  strength for the torque imparted by the input shaft  12  at the press fit spline connection. An aluminum piston  52  replaces the OE overrun piston with a larger inner diameter as at  54  to fit the overrun sleeve  50  and uses an O-ring  56  for the fluid seal at the overrun piston sleeve  50 /overrun piston  52  interface. The outer diameter, as indicated at  58 , of the overrun piston  52  uses a lip seal  60  for the fluid seal at the interface with the forward piston  16 . A small amount of overrun piston apply area (the piston area on which fluid pressure is applied) was sacrificed for the additional overrun sleeve  50  strength. The loss of overrun clutch apply force from the overrun piston was not found to be a concern for the target high performance applications. However, as noted above, increasing the strength (e.g., torque capacity) with the aftermarket overrun piston sleeve  50  shifted failure to the input housing  14  near the splined connection in the area of the forward piston  16 . 
     Accordingly there is a need for a kit and/or components to strengthen the input housing near the splined connection in the forward piston area. Desirably, such a kit and/or components work in conjunction with an aftermarket kit and/or components that strengthen the input housing near the splined connection in the overrun piston area. More desirably still, such a kit and/or components can accommodate torque levels in high performance applications in excess of the original OE design specifications for the input housing. 
     SUMMARY 
     According to an embodiment, a kit for modifying a transmission input housing is disclosed. The input housing has an outer case portion and an inner stepped conical portion. The input housing is configured to receive an input shaft at an inner surface of the inner stepped portion. The inner stepped portion has a wall thickness that decreases from a forward piston area inward and has an overrun piston region and a forward piston region. 
     In embodiments the kit includes an overrun piston sleeve fixedly positioned on an inner surface of the input housing inner stepped portion at the overrun region. The kit further includes an overrun piston having an inner diameter configured to mate with the overrun piston sleeve. The inner diameter of the overrun piston is larger than an inner diameter of an OE overrun piston. A seal is positioned between the overrun piston and the overrun piston sleeve at an inner diameter of the overrun piston. 
     In embodiments a forward piston sleeve is fixedly positioned on the outer surface of the input housing inner stepped portion adjacent the overrun sleeve. A forward piston having an inner diameter configured to mate with the forward piston sleeve has an inner diameter that is larger than an inner diameter of an OE forward piston. 
     Seals are positioned between the forward piston and the forward piston sleeve, between the overrun piston and the forward piston at an outer diameter of the overrun piston, and between the forward piston outside diameter and the forward piston housing. 
     In embodiment, the seal between the overrun piston and the overrun piston sleeve can be an O-ring seal and the seal between the forward piston and the forward piston sleeve can be a lip seal. The seal between the overrun piston and the forward piston can be is a lip seal. 
     In embodiments, a fluid apply area of the forward piston is about equal to a fluid apply area of an OE forward piston. The kit can further include a forward piston housing. 
     The forward piston sleeve and the forward piston housing can be formed from steel. The forward piston can be formed from aluminum. 
     In another aspect, the kit can include a replacement forward piston housing, a forward piston sleeve fixedly positioned on the outer surface of the input housing inner stepped portion, and a replacement forward piston adjacent the replacement forward piston housing. The replacement forward piston can have an inner diameter configured to mate with the forward piston sleeve, and the forward piston can have an inner diameter that is larger than an inner diameter of an OE forward piston. The kit can further include seals positioned between the forward piston and the forward piston sleeve. 
     In embodiments, a fluid apply area of the forward piston is about equal to a fluid apply area of an OE forward piston. 
     In another aspect, a kit for modifying a transmission input housing, which input housing has an outer case portion and an inner stepped conical portion, and which input housing is configured to receive an input shaft at an inner surface of the inner stepped portion, the inner stepped portion having a wall thickness that decreases from a forward position inward, the input housing having an overrun piston region and a forward piston region, the forward piston region having a forward piston housing, includes a forward piston sleeve fixedly positioned on the outer surface of the input housing inner stepped portion, a replacement forward piston adjacent the replacement forward piston housing, the replacement forward piston having an inner diameter configured to mate with the forward piston sleeve, the forward piston having an inner diameter being larger than an inner diameter of an OE forward piston, and a seal positioned between the forward piston and the forward piston sleeve. 
     The kit can be configured such that a fluid apply area of the forward piston is about equal to a fluid apply area of an OE forward piston. The forward piston sleeve can be formed from steel, and the forward piston can be formed from aluminum. 
     A method for increasing the strength of a transmission input housing includes installing a replacement forward piston housing, installing a forward piston sleeve on the outer surface of the input housing inner stepped portion adjacent the overrun sleeve, installing a forward piston on the forward piston sleeve, the forward piston having a larger inner diameter than an inner diameter of an OE forward piston, and installing a seal between the forward piston and the forward piston sleeve. 
     The method can further include installing an overrun piston sleeve on an outer surface of the input housing inner stepped portion at the overrun region, installing an overrun piston on the overrun piston sleeve, the overrun piston having a larger inner diameter than an inner diameter of an OE overrun piston, installing a seal between the overrun piston and the overrun piston sleeve at an inner diameter of the overrun piston, and installing a seal between the overrun piston and the forward piston. 
     These and other features, and advantages of the disclosure will be apparent from the following description, taken in conjunction with the accompanying sheets of drawings, wherein like numerals refer to like parts, elements, components, steps, and processes. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIGS. 1A-1C  are sectional and partial sectional views of an original equipment (OE) transmission input housing and direct and overrun clutch packs; 
         FIGS. 2A-2C  are sectional and partial sectional views of a transmission input housing, forward and overrun clutch packs, and includes an aftermarket overrun sleeve kit; and 
         FIGS. 3A-3C  are sectional and partial sectional views of a transmission input housing, forward and overrun clutch packs, and includes an aftermarket overrun sleeve kit and input forward housing sleeve components in accordance with an embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     While the present disclosure is susceptible of embodiment in various forms, there is shown in the drawings and will hereinafter be described one or more embodiments with the understanding that the present disclosure is to be considered illustrative only and is not intended to limit the disclosure to any specific embodiment described or illustrated. 
       FIGS. 1A-1C  illustrate portions of an OE transmission, showing among other components, an input section  10 , having an input housing  14 , and input shaft  12 . The shaft  12  is splined to the housing  14  to effect transfer of torque from the input shaft  12  to the transmission via the housing  14 . The input housing  14  has an outer case portion  70  and an inner stepped conical portion  72 . Some of the components within the transmission are disposed between the outer case portion  70  and an outer surface  74  of the stepped conical portion  72 . The components include, for example, the forward piston housing  24 , the forward piston  16 , the overrun piston  18 , the forward clutch pack  20  and the overrun clutch pack  22 . 
     The input shaft  12  is splined to the input housing  14  at an inner surface  76  of the stepped conical portion  72 . As seen in the figures, the wall thickness of the stepped portion  72  is greatest at a location at about the forward piston housing  24  and decreases moving inward, to the location at which the overrun piston  18  is positioned to the housing  14  opposite the input shaft  12 . 
     As noted previously one prior aftermarket kit and components include a steel overrun sleeve  50  installed onto the input housing  14  at about the overrun piston  52 . The sleeve  50  is installed on the housing  14  with an interference fit. The overrun sleeve  50  increases the strength of the input housing  14  to withstand the torque imparted by the input shaft  12  at the press fit spline connection. 
     To accommodate the sleeve  50  (now oversized at the input housing  14  at the splined connection), a replacement overrun piston  52  replaces the OE overrun piston  18 . The replacement overrun piston  52  has a larger inner diameter as indicated at  54  to fit over the overrun sleeve  50 . A known aftermarket overrun piston  52  is formed from aluminum. The inner diameter at  54  includes a flange  64  having a circumferential groove  66 . The seal  56 , such as the illustrated O-ring seal is positioned in the groove  66  at the overrun sleeve  50 /overrun piston  52  interface  54 . The lip seal  60  is positioned at the outer diameter  58  of the overrun piston  52  at the overrun piston  52 /forward piston  16  interface to provide a fluid seal at the interface of the overrun piston  52  and the forward piston  16 . 
     Increasing the strength (e.g., torque capacity) of the input housing  14  at the replacement or aftermarket overrun piston  52  area shifted failure of the input housing  14  near the splined connection from the area at the overrun piston  52  to the area at the forward piston  16 . 
     Referring now to  FIGS. 3A-3C , there is shown a portion of a modified OE transmission, showing among other components, the input section  10 , input housing  14  and input shaft  12 . The illustrated transmission includes the overrun sleeve  50  and replacement overrun piston  52 , O-ring seal  56  at the overrun sleeve  50 /overrun piston  52  interface  54 , and lip seal  60  at the outer diameter  58  of the overrun piston  52 . 
     To strengthen the input housing  14  at the forward piston region  84 , a sleeve  86  is installed onto the outer surface  74  of the stepped conical portion  72  of the housing  14  at about the forward piston region  84 . That is, the forward sleeve  86  is installed onto the input housing  14  on the diameter that originally interfaced with the OE forward piston  16  (the step outward relative to the overrun piston  52  area). In an embodiment, the forward sleeve  86  is installed with a press or interference fit on the input housing  14 . Other ways in which the forward sleeve  86  is installed on the input housing  14  such as other mechanical bonding, adhesives and the like will be recognized by those skilled in the art and are within the scope and spirit of the present disclosure. 
     A replacement forward piston  88  has an inner diameter, as indicated at  94 , that mates with the outer diameter of the forward piston sleeve  86 . A seal  92 , such as a lip seal is present at the inner diameter (at the interface of the forward piston inner diameter as indicated at  94 , and the forward piston sleeve  86 ) to provide a fluid seal for the forward piston  88 . The forward piston  88  is configured for use with the replacement overrun piston  52  and its outer lip seal  60 . In an embodiment, the replacement forward piston  88  is formed from aluminum. 
     A replacement forward piston housing  96  is positioned adjacent the forward piston  88 . The replacement forward piston housing  96  has nearly the same inner and outer diameters (as indicated at  98 ,  100 ) as the OE forward piston housing  24  but is configured to accommodate the replacement forward piston  88 . 
     The outer diameter  90  of the forward piston  88  mates with the forward piston housing  96 , and a seal  97 , such as the illustrated lip seal, provides a fluid seal between the forward piston housing  96  and the forward piston  88 . The outer diameter  90  of the forward piston  88  and mating inner diameter  94  of the forward piston housing  96  are larger than the OE components they replace. The increase in diameters compensates for the fluid apply area that that is reduced by the forward piston sleeve  86 . The fluid apply area of the forward piston  88  closely approximates the OE forward piston  16  apply area. The inner diameter, as indicated at  98 , of the forward piston housing  96  mates with the input housing  14  and a seal  102 , such as the illustrated O-ring, provides a fluid seal between the forward piston housing  96  and the stepped surface  72  of the input housing  14 . 
     It will be appreciated that the forward sleeve components and/or kit are designed to interact and function with the surrounding OE components. Transmission clutch pack application and release functionality remains essentially the same while the input housing will have significantly higher torque capacity. 
     In embodiments, the forward piston sleeve  86  is formed from steel. It is, however, anticipated that the forward piston sleeve  86  can be formed from other materials, such as aluminum, having varying degrees of strength. The fitment of the forward piston sleeve  86  to the housing  14  can be a press or interference fit on the input housing  14 . Other ways in which the forward sleeve  86  can be bonded or secured to the input housing  14  such as other mechanical bonding, adhesives and the like will be recognized by those skilled in the art and are within the scope and spirit of the present disclosure. 
     The replacement forward piston  88  can also be fabricated from a variety of materials, such as aluminum, steel or other suitable materials. Likewise, the forward piston housing  96  can be fabricated from aluminum, steel or other suitable materials. 
     It is envisioned that a new or replacement forward piston sleeve  86  and forward piston  88  can be used with an existing (OEM) or previously installed replacement overrun piston sleeve  50  and piston  52 . In such a configuration the forward piston  88  has an inner diameter that is larger than an inner diameter of an OE forward piston, and a seal  97  is positioned between the forward piston  86  and the forward piston sleeve  88 . In this configuration a fluid apply area of the forward piston  86  is about equal to a fluid apply area of an OE forward piston. The forward piston sleeve  86  can be formed from steel, and the forward piston  88  can be formed from aluminum. 
     It is also envisioned that a single, combined forward piston and overrun piston sleeve (not shown) can be used (to replace the individual overrun piston sleeve and forward piston sleeve) to reduce the number of parts to be replaced in the input housing  14 . The seals, such as the illustrated lips seals could be any of a variety of suitable seal types including for example, O-rings, D-rings, X-rings, polytetrafluoroethylene (PTFE) seals, and the like. Likewise, the illustrated O-rings can also be of any suitable type of seal, such as O-rings, b-rings, X-rings, polytetrafluoroethylene (PTFE) seals, and the like. 
     In an aspect, a kit  104  to increase the strength of a transmission input housing includes a forward piston sleeve  86  configured for installation on the input housing  14  at the outer surface of the stepped conical portion  72  of the housing  14  at about the forward piston  88  area. The kit  104  further includes a replacement forward piston  88  having a larger inner diameter  94  configured for installation on the forward piston sleeve  86 , and a replacement forward piston housing  96 . The forward piston  88  can have a larger outer diameter  90  as well. The kit  104  can further include seals, such as one or more O-ring seals, lip seals or the like. 
     In an embodiment, the kit  104  includes an overrun piston sleeve  50  configured for installation on the input housing  14  at the outer surface  74  of the stepped conical portion  72  of the housing at about the overrun piston  52  area. The kit  104  can include a replacement overrun piston  52  having a larger inner diameter  54  configured for installation on the overrun piston sleeve  50 . The kit  104 , with the replacement overrun piston  52  can include still further seals, such as one or more O-ring seals, lip seals of the like. 
     In an embodiment, the kit can include a single sleeve that combines the overrun piston sleeve and the forward piston sleeve. Such a kit can further include a replacement forward piston, a replacement forward piston housing and a replacement overrun piston. 
     A method of increasing the strength of a transmission input housing includes, in the input housing, installing a forward piston sleeve on the input housing at the outer surface of the stepped conical portion of the housing at about the forward piston area. The method further includes installing a replacement forward piston having a larger inner diameter on the forward piston sleeve, and installing a replacement forward piston housing. The method further includes installing seals, such as one or more O-ring seals and/or one or more lips seals at least between the forward piston and the forward piston housing and between the forward piston and the forward piston sleeve. 
     The method can also include installing an overrun piston sleeve on the input housing at the outer surface of the stepped conical portion of the housing at about the overrun piston area and installing a replacement overrun piston having a larger inner diameter on the overrun piston sleeve, and installing seals, such as one or more O-ring seals and one or more lips seals at least at between the overrun piston and the overrun piston sleeve and between the overrun piston and the forward piston. 
     In a method installing the overrun piston sleeve and the forward piston sleeve is installing a single sleeve at the outer surface of the stepped conical portion of the housing at about the forward piston and the overrun piston areas that extends over and between the forward piston and the overrun piston areas. 
     It is understood that although the present kit and components for modifying a transmission input housing is described and illustrated in connection with certain General Motors 4L60 series (4L60, 4L60E, 4L65E) and 4L70E automatic transmissions, the present kit and components can be used with other automatic transmissions and that such other uses are within the scope and spirit of the present disclosure. In addition, it will be appreciated that the features described with respect to any of the embodiments above may be implemented, used together with, or replace features described in any of the other embodiments above. It is further understood that the description of some features may be omitted in some embodiments, where similar or identical features are discussed in other embodiments. 
     All patents referred to herein, are hereby incorporated herein in their entirety, by reference, whether or not specifically indicated as such within the text of this disclosure. 
     In the present disclosure, the words “a” or “an” are to be taken to include both the singular and the plural. Conversely, any reference to plural items shall, where appropriate, include the singular. In addition, it is understood that terminology referring to directions or relative orientations, such as, but not limited to, “forward” “rearward” “inner” “outer” “upper” “lower” “raised” “lowered” “top” “bottom” “above” “below” “alongside” “left” and “right” are used for purposes of example and do not limit the scope of the subject matter described herein to such orientations or relative positioning. 
     From the foregoing it will be observed that numerous modifications and variations can be effectuated without departing from the true spirit and scope of the novel concepts of the present invention. It is to be understood that no limitation with respect to the specific embodiments illustrated is intended or should be inferred. The disclosure is intended to cover by the appended claims all such modifications as fall within the scope of the claims.