Abstract:
An Automatic Transmission Input Drum Support Ring and Method is disclosed. Also disclosed is a support ring that is installable on the input drum of a conventional General Motors 700R4 automatic transmission in order to prevent overtorque-related cracking of this component. The device is configured to permit the transmission oiling/piston system to function as originally designed. The method for reinforcing a conventional transmission involves the installation of the support ring without the need for substantial modification of the conventional transmission.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    This invention relates generally to transmission accessories and, more specifically, to an Automatic Transmission Input Drum Support Ring and Method.  
           [0003]    2. Description of Related Art  
           [0004]    The General Motors 700R4/4L60E automatic transmission is one of the most popular transmissions for use in performance-enhanced rear-wheel drive or four-wheel drive vehicles. Its popularity comes from its shift spacing, its wide cross-platform acceptance, and its lightweight design. Unfortunately, there has been one recurring problem associated with this transmission model, namely, the cracking of the input drum due to the input drum&#39;s inability to withstand the shaft torque created by performance engines. If not for the input drum cracking problem, the 700R4/4L60E transmission would be “unbreakable,” even in a performance vehicle drive train, since the rest of the transmission is extremely durable. The industry has recognized this problem and has attempted to cure it by replacing the entire casing of the input drum with a “beefed up,” more durable casing that allegedly can withstand more torque than the original equipment casing. There are two problems with this solution:  
           [0005]    (1) the exchange of the entire input drum casing is fairly expensive and requires disassembly of a substantial portion of the transmission; and (2) while the torque handling capacity of the new casing is in excess of the original equipment, it still does not eliminate the problem, but only extends the durability somewhat. What is needed, then is a device and method to strengthen the original 700R4/4L60E transmission input drum substantially without necessitating a transmission rebuild, and at a fairly low cost.  
         SUMMARY OF THE INVENTION  
         [0006]    In light of the aforementioned problems associated with the prior devices and systems, it is an object of the present invention to provide an Automatic Transmission Input Drum Support Ring and Method. The support ring should be installable on the input drum of a conventional General Motors 700R4 automatic transmission in order to prevent overtorque-related cracking of this component. The device should be configured to permit the transmission oiling/piston system to function as originally designed. The method for reinforcing a conventional transmission should involve the installation of the support ring without the need for substantial modification of the conventional transmission.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0007]    The objects and features of the present invention, which are believed to be novel, are set forth with particularity in the appended claims. The present invention, both as to its organization and manner of operation, together with further objects and advantages, may best be understood by reference to the following description, taken in connection with the accompanying drawings, of which:  
         [0008]    [0008]FIG. 1 is a partially exploded side view of a conventional automatic transmission;  
         [0009]    [0009]FIGS. 2A and 2B are end and side views of the sprocket assembly of the automatic transmission of FIG. 1;  
         [0010]    [0010]FIG. 3 is a partial cutaway side view of the input shaft sleeve portion of the transmission of FIGS. 1 and 2;  
         [0011]    [0011]FIGS. 4A and 4B are partial cutaway side views of the input shaft sleeve portion of the transmission of FIGS. 1-3 having the support ring device of the present invention installed thereon;  
         [0012]    [0012]FIG. 5 is an end perspective view of the support ring device of FIG. 4; and  
         [0013]    [0013]FIG. 6 is a cutaway side view of the support ring device of FIGS. 4 and 5.  
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0014]    The following description is provided to enable any person skilled in the art to make and use the invention and sets forth the best modes contemplated by the inventor of carrying out his invention. Various modifications, however, will remain readily apparent to those skilled in the art, since the generic principles of the present invention have been defined herein specifically to provide an. Automatic Transmission Input Drum Support Ring and Method.  
         [0015]    The present invention can best be understood by initial consideration of FIG. 1. FIG. 1 is a partially exploded side view of a conventional automatic transmission  10 . The outer casing  12  contains a number of components, including bearings, clutch plates, shaft segments, etc.; only those components critical to understanding the present invention have been depicted here in the interest of simplicity and clarity.  
         [0016]    Extending from one end of the casing  12  is an output shaft  14 , which is where the drive shaft and/or other mechanical components are attached to transmit power from the transmission  10  to the wheels. The input end  15  of the casing  12  is configured to attach to the engine itself. Shown here in an exploded view are the pertinent components to the advancement of the present invention. First is the input shaft  22 , which is the actual power-takeoff connection to the engine. The input shaft  22  engages the sprocket assembly  20 , which protrudes (to the right in this view) from the input drum casing  18 . The sprocket assembly  20  and input drum casing  18  are integrated members that together comprise the assembly known as the input drum  16 . When assembled, the input drum  16  is housed completely within the casing  12 . Now turning to FIG. 2, we can examine the environment of the present invention more closely.  
         [0017]    [0017]FIGS. 2A and 2B are end and side views of the sprocket assembly  20  of the automatic transmission of FIG. 1, absent the input drum casing (see FIG. 1) which has been eliminated in this view in the interest of simplicity. The sprocket assembly  20  is actually a single member having a gear or sprocket  24  at one end and a plurality of piston steps  26  at its other (input) end. When the transmission parts are completely assembled, the piston steps  26  serve as the inner surfaces of piston chambers that actually cause the transmission to operate (at least in part). The piston steps  26  gradually taper down until terminating at the overrun piston step  28 . The overrun piston step has an input shaft bore  30  formed in it to accept the input shaft therein (see FIG. 1). The walls of the input shaft bore  30  have a plurality of splines  32  extending therefrom to engage corresponding splines extending outwardly from the input shaft (see FIG. 1). Just beyond the end of the splines  32  is located a oil passage  34  which permits hydraulic transmission fluid to pass between the interior and the exterior of the sprocket assembly  20  (i.e. the pistons). Turning to FIG. 3, we can examine exactly what problem the device and method of the present invention has been created to solve.  
         [0018]    [0018]FIG. 3 is a partial cutaway side view of the sprocket assembly  20  of the transmission of FIGS. 1 and 2. As depicted here, the input shaft  30  has been inserted into the overrun piston step  28  of the sprocket assembly  20  such that the splines engage between the two. The problem with the 700R4/4L60E transmission is that cracks  36 , such as the one shown here, have a tendency to develop when the input shaft is subjected to power in excess of 250 horsepower, or even under lower power conditions over prolonged periods of time. Once a crack  36  develops, the transmission must be rebuilt or replaced. In order to correct this problem, the invention described below commencing with FIG. 4 was developed.  
         [0019]    [0019]FIGS. 4A and 4B are partial cutaway side views of the sprocket assembly  20 , and more specifically the overrun piston step  28  of the transmission of FIGS. 1-3 having the support ring device  40  of the present invention installed thereon. The device  40  is configured to be heated and pressed onto the overrun piston step  28  of the sprocket assembly  20 . On cooling, an interference fit between the two elements that results in the support ring device  40  being held snugly thereto. Once the ring  40  is attached, the input shaft (see FIG. 3) can be inserted into the input shaft bore  30 . The additional reinforcement resulting from the installation of the ring  40  strengthens the overrun piston step  28  substantially, without the need for expensive replacement drum assemblies. In fact, testing demonstrates that a transmission having undergone this modification enables it to withstand in excess of 400 horsepower without cracking the input shaft portion  28 . It should be noted that the overrun piston (not shown) resides over the overrun piston step  28  when the transmission is fully assembled; the addition of the support ring device  40  will increase the diameter of the step  28 , such that some modification to the overrun piston (not shown) will be necessary so that it might fit over both the overrun piston step  28  and the support ring device  40 . Turning to FIGS. 5 and 6, we can examine further detail regarding the present invention.  
         [0020]    [0020]FIG. 5 is an end perspective view of the support ring device  40  of FIG. 4. FIG. 6 is a cutaway side view of the support ring device  40  of FIGS. 4 and 5. The device  40  comprises a body  42  having a generally circular cross section. The body  42  further defines an a sprocket end  44  which is closest to the sprocket (see FIGS. 1-3) when installed on an input drum, and a shaft end  46  which is closest to the open end of the overrun piston step (see FIG. 4).  
         [0021]    The body  42  further is defined by an outer surface  50  and an inner surface  48 ; as discussed above, the inner diameter  58  of the ring  40  is designed cooperatively with the outer diameter of the overrun piston step (see FIG. 4) to allow the ring  40  to slip over the overrun piston step when the ring is heated sufficiently, but yet to create an interference fit once the ring  40  has cooled.  
         [0022]    The sprocket end  44  of the ring  40  defines an outer rim  52  and an inner rim  54 ; the inner rim  54  has a smaller outer diameter than the outer rim  52 , such that a channel  55  is formed therebetween. Furthermore, a lubricating notch  56  is formed at the sprocket end  44  of the ring  40 . When the ring  40  is installed onto a overrun piston step (see FIG. 4), the notch  56  is aligned with the oiling passage (see FIGS. 3 and 4) so that hydraulic fluid will not be obstructed by the ring  40  from flowing through the oiling passage. The channel  55  further aides in distributing hydraulic fluid around the circumference of the ring  40  as a safety measure in case the ring  40  begins to slip and a misalignment occurs between the notch  56  and the oiling passage (see FIGS. 3 and 4).  
         [0023]    Those skilled in the art will appreciate that various adaptations and modifications of the just-described preferred embodiment can be configured without departing from the scope and spirit of the invention. Therefore, it is to be understood that, within the scope of the appended claims, the invention may be practiced other than as specifically described herein.