referring to the drawings , specifically fig1 , 6 and 7 , a preferred sub - frame attachment apparatus 10 is illustrated . as described in more detail below , the attachment apparatus 10 includes a pin 12 and a shear bulkhead 14 that provide the necessary stiffness at a sub - frame connection point on the vehicle &# 39 ; s rear frame , within the vehicle body frame elements , namely an upper part of the frame 22 , a lower part of the frame 20 , and a sub - frame mounting bracket 18 . thus , an improved joint between the vehicle body and rear sub - frame 90 may be formed . referring to fig6 and 7 , a portion of the rear frame 16 is shown and includes a lower part 20 and an upper part 22 . the lower part of the frame 20 includes a first flange 24 and a second flange 26 , a first sidewall 28 , a second sidewall 30 and a base 32 . the upper part 22 of the frame includes a first flange 34 and a second flange 36 , a first sidewall 38 and a second sidewall 40 , a first lateral portion 42 and a second lateral portion 44 and a channel 46 . within a preferred form of the lower part of the frame 20 , the base 32 is located between , and is generally perpendicular to , the first and second body sidewalls 28 and 30 . the body sidewalls 28 and 30 have generally equivalent heights . the base 32 joins each of the first and second sidewalls 28 and 30 at their bottom ends . the base 32 and sidewalls 28 and 30 , in combination , form an open topped duct . the base 32 also defines an aperture therein . the first flange 24 and second flange 26 , respectively , extend from the top end of each body sidewall 28 and 30 in a direction away from the inside of the duct . each of the first and second flanges 24 and 26 is generally parallel to the base 32 . within a preferred form of the upper part of the frame 22 , the channel 46 is located between the first lateral section 42 and the second lateral section 44 and at a lower height than the lateral sections . the channel 46 includes a flat bottom 50 and angled sides 52 . the bottom 50 defines an aperture 54 . the angled sides 52 extend from the bottom 50 to the lateral sections 42 and 44 of the upper part of the frame 22 . the lateral sections 42 and 44 have equivalent widths and are generally parallel to the bottom 50 of the channel 46 . the first sidewall 38 is located on an opposite side of the first lateral section 42 from the channel 46 . similarly , the second sidewall 40 is located on an opposite side of the second lateral section 44 from the channel 46 . the sidewalls 38 and 40 are generally planar , but are curved at their upper and lower ends . each sidewall 38 and 40 is generally perpendicular to the adjacent lateral section 42 and 44 . the first flange 34 of the upper part of the frame 22 extends from the opposite end of the first sidewall 38 as the first lateral section 42 , extends in an opposite direction compared to the first lateral section 42 , and is generally parallel to the first lateral section 42 . the second flange 36 of the upper part of the frame 22 extends from the opposite end of the second sidewall 40 as the second lateral section 44 , extends in an opposite direction compared to the second lateral section 44 , and is generally parallel to the second lateral section 44 . the sub - frame mounting bracket 18 includes a generally flat base 56 and at least one side wall 58 that is generally perpendicular to the base 56 . the flat base 56 defines an aperture therein . the mounting pin 12 is preferably formed from round stock and includes a top end 60 , a generally middle section 62 , and a bottom end 64 . the bottom end 64 is beveled around its circumference 66 . the pin 12 includes a collar 68 located approximately one quarter of the way between the bottom end 64 and top end 60 . the collar 68 has an outer edge 70 that is beveled . referring to fig5 - 7 , the shear bulkhead 14 is a generally planar element that includes generally perpendicular flanges at its top , bottom and side edges . the top flange 72 , bottom flange 74 , and at least one of the side flanges 76 and 78 preferably extend from the shear bulkhead 14 in a common direction which is away from the mounting pin when the apparatus 10 is assembled . the shear bulkhead 14 also includes an indented channel 80 ( not in the same plane with the rest of the bulkhead ) that extends from the bottom edge of the shear bulkhead 14 to the top edge . the channel 80 has a rounded configuration . the shear bulkhead 14 is shaped to fit within the surrounding frame 16 . in a preferred first embodiment shown in fig6 and 7 , the shear bulkhead 14 is symmetrical and is wider at its top than at its bottom . the shape of the shear bulkhead is limited somewhat by the constraints of the frame shape . the flanges add stiffness to the shear bulkhead . in a variation of the first embodiment , the bulkhead on one side of the channel 80 has a greater surface area than on the opposite side . referring to fig1 , the rear sub - frame 90 , a portion of which is illustrated , is attached to the vehicle body 92 in four positions ( only one position is shown ). in each position , a mounting pin 12 and shear bulkhead 14 are used to provide the requisite stiffness in the vehicle body 92 at the attachment point 96 . referring to fig6 and 7 , the attachment apparatus 10 is assembled by placing the shear bulkhead 14 within the upper and lower parts of the frame 20 and 22 . the side flanges 76 and 78 of the shear bulkhead 14 are spot welded ( shown by shaded spots ) to the lower part of the frame 20 . depending on the size of the side flanges , one or two welds are required per flange . the mounting pin 12 is then inserted into the frame 16 through the hole in the base 32 of the lower part of the frame 20 . the mounting pin 12 is advanced until it reaches the top of the upper part of the frame 22 . preferably , a portion of the mounting pin 12 extends through the aperture 54 in the upper part 22 of the frame . the sub - frame mounting bracket 18 is then placed over the bottom end of the mounting pin 12 and advanced until contact with the collar 68 on the mounting pin 12 is made . the mounting pin 12 is mig welded ( shown by hollow ovals ) near its top to the channel 46 of the upper part of the frame 22 . the mounting pin 12 is mig welded at its generally middle section 62 to the channel 80 in the shear bulkhead 14 . the mounting pin 12 is projection welded ( shown by crossed ovals ) just below its collar 68 to the sub - frame mounting bracket 18 . the upper and lower parts 20 and 22 of the frame are also welded together as known in the art . referring to fig1 , at the sub - frame attachment points 96 , a portion of the sub - frame 90 includes an aperture fitted with a bushing and the bushing is pushed over the lower end 98 of the mounting pin 12 . a bolt ( not shown ) is then secured to the mounting pin 12 in order to hold the sub - frame 90 to the frame 92 . referring to fig8 and 9 , a second embodiment of the apparatus is shown . elements that are the same as within the first embodiment are referred to with the same reference numbers . the mounting pin 112 of the apparatus 110 is preferably formed from round stock and includes a top end 160 , a generally middle section 162 , and a bottom end 164 . the mounting pin 112 within the second embodiment of the apparatus is shorter than the mounting pin 12 in the first embodiment of the apparatus . the bottom end 164 is beveled around the circumference 166 . the pin 112 includes a collar 168 located about one quarter of the way between the bottom end 164 and top end 160 . the collar 168 has an outer edge 170 that is beveled . the shear bulkhead 114 is a generally planar element that includes perpendicular flanges at its top , bottom and side edges . the top flange 172 , bottom flange 174 , and side flanges 176 and 178 preferably all extend from the shear bulkhead 114 in a common direction . the shear bulkhead 114 also includes a weld tab 173 extending from the top flange 172 . the shear bulkhead 114 also includes an indented channel 180 that extends from the bottom edge of the shear bulkhead 114 to the top edge . the shear bulkhead 114 of the second embodiment is taller than the shear bulkhead 14 of the first embodiment of the apparatus and is shaped to fit within the surrounding frame 16 . within the second embodiment , the shear bulkhead 114 preferably has a width that is more narrow at is bottom than at its generally middle section and top , although other shapes are possible as shown in fig5 . additionally , the width of the shear bulkhead is preferably narrower at the top than at its generally middle section . referring to fig8 and 9 , the attachment apparatus 110 is assembled with the shear bulkhead 114 placed inside of the upper and lower parts of the frame 16 . the shear bulkhead 114 extends up to the lower side of the first and second transverse portions 42 and 44 of the upper part of the frame 22 . the side flanges 176 and 178 are spot welded to the sides of the upper or lower part of the frame and the welding tab 173 is mig welded to the upper part of the frame 22 . the mounting pin 112 is then slid into the hole in the base of the lower part of the frame 20 and advanced until the top of mounting pin 112 has reached about three quarters of the height of the shear bulkhead 114 . the mounting pin 112 fits into the channel 180 of the shear bulkhead 114 . the mounting pin 112 is then mig welded to the shear bulkhead 114 above the generally middle section 162 of the mounting pin 112 . the sub - frame mounting bracket 18 is then placed over the lower end of the mounting pin 112 and moved toward the frame 16 until the collar 168 on the mounting pin stops upward movement . the mounting pin 112 is then projection welded just below the collar 168 to the sub - frame mounting bracket 18 . referring to fig1 , an apparatus of the first embodiment is used where the front part of the rear sub - frame attaches to the vehicle and an apparatus of the second embodiment attaches to the rear part of the rear sub - frame of the vehicle . in the first embodiment , several different configurations of the frame are possible depending upon the location of the connection point on the vehicle body . each configuration though has at least an upper surface that defines an aperture whereby the mounting pin is welded to the upper part of the frame adjacent to the aperture . additionally , each configuration of the frame has two side surfaces whereby the side flanges on the shear bulkhead are welded to the frame side surfaces . correspondingly , the shear bulkhead 14 has varying shapes because the shear bulkhead shape matches , in general , the shape of the inside of the frame . also , in the second embodiment , several different configurations of the frame are possible depending upon location on the vehicle body . each configuration of the frame , though , has at least a generally flat surface whereby the welding tab on the shear bulkhead is weldable to this flat surface of the upper part of the frame . additionally , each configuration of the frame has two side surfaces whereby the side flanges on the shear bulkhead are weldable to the side surfaces . in the first and second embodiments , several different configurations of the sub - frame mounting bracket are possible depending upon the location on the vehicle body . each configuration though has at least a flat surface that defines an aperture whereby the mounting pin is welded to the flat surface just below the mounting pin collar . in the first and second embodiments , alternatively , either a round mounting pin or hex mounting pin may be used . a portion of , or the entire mounting pin may be hollow . although the apparatus and method have been shown and described with reference to certain preferred and alternate embodiments , the apparatus and method are not limited to these specific embodiments . minor variations and insubstantial differences in the various combinations of materials and methods of application may occur to those of ordinary skill in the art while remaining within the scope of the apparatus and method as claimed and equivalents .