referring first to fig5 and 6 , a preferred embodiment of a roller clutch made according to the invention , indicated generally at 60 , is installed between an inner pathway race , indicated generally at 62 , and an outer cam race 64 . the races 62 and 64 are incorporated within a disk pack 66 of an automotive automatic transmission . when the disk pack 66 is compressed by a piston 68 , torque is transferred between the races 62 and 64 when , and only when , the races 62 and 64 are turning at the same speed , and the roller clutch 60 can lock up , which gives a smooth shift feel . efficient lock up is dependent upon maintaining a close concentricity between the races 62 and 64 . when the disk pack 66 is de - activated , a pressurized oil stream is pumped from around a central shaft 70 to and through the races 62 and 64 , and ultimately out to and through the disk pack 66 to lubricate it . the pressurized oil is delivered to the disk pack 66 efficiently only if it is transferred radially from inner race 62 to and through outer race 64 without a great deal of pressure loss past the clutch 60 . clutch 60 provides both good concentricity control and superior pressurized oil retention , through simple but independently acting structural features . referring next to fig7 and 9 , details of the races 62 and 64 are illustrated . inner pathway race 62 is basically conventional in size and shape , with a cylindrical inner pathway 72 . four evenly spaced oil passages 74 open radially through pathway 72 . outer race 64 has several conventional features , including the familiar saw - tooth shape comprised of fourteen evenly circumferentially spaced , shallow sloped cam ramps 76 , steeply sloped cam hooks 78 , and intervening semi cylindrical pads 80 . four evenly spaced pairs of oil passages 81 open from selected cam ramps pathway radially through the outer race 64 and to the disk pack 66 . when the races 62 and 64 are coaxial , the pads 80 do have a substantially consistent radial spacing rs from the pathway 72 . however , that feature is not used for concentricity control between the races 62 and 64 . instead , machined into each annular end face of the cam race 64 is a cylindrical pilot surface 82 , which has a diameter large enough to rest well clear and radially outboard of the cam ramps 76 . when the races 62 and 64 are coaxial , pilot surface 82 has a predetermined radial spacing from the pathway 72 , indicated at x . machined adjacent to and just axially inboard of each pilot surface 82 is a circular retention groove 84 , of larger diameter , and with a consequently larger radial spacing y from the pathway 72 . each pair of adjacent pilot surfaces 82 and retention grooves 84 is evenly axially spaced to either side of a central plane pc , with enough axial space z between to accommodate the wedging elements , which are further described below . it is far simpler to precisely machine cylindrical and circular surfaces like 82 and 84 , as compared to saw - toothed surfaces like 76 and 78 , or even discontinuous semi cylindrical surfaces like 80 . it is therefore possible to more precisely determine and maintain radial clearances like x and y , which is used to advantage in the invention . referring next to fig1 through 17 , the basic structural framework of roller clutch 60 is a pair of plastic molded cage halves , indicated generally at 86 and 88 respectively . each is a mirror image of the other relative to the central plane pc , rather than absolutely identical , since they are installed from opposite axial directions . nevertheless , each is identical in size , and , relative to the central plane , identical in shape as well . therefore , the specific structural features of cage half 86 are described and numbered , and the equivalent , mirrored features of the other cage half 88 are given the same number primed (&# 39 ;). cage half 86 comprises a series of closely and evenly circumferentially spaced annular sections , 90 , equal in number to the number of cam ramps 76 . each arcuate section 90 has a radial width wp , measured from inner to outer edge , that is very slightly less than the radial spacing x , as defined above , a radial differential as small as about 0 . 25 diametral . this small radial differential is ultimately used to control concentricity . the circumferential length of each annular section 90 is relatively large , substantially equal to either side a or b of the wedging space as defined above . therefore , most of the 360 degree circumference is subtended by the fourteen annular sections 90 together . each arcuate section also has an axial thickness that is substantially equal to the total axial thickness of either side by side pilot surface - retention groove pair 82 - 84 which , in conjunction with the significant total circumferential length of all the sections 90 , creates a significant amount of total inner and outer edge surface area available for concentricity control . each cage half annular section 90 is integrally molded with a retention and sealing ring section 92 that extends radially outwardly thereof by slightly less than the radial depth of the retention groove 84 , and with an equal circumferential length . the total radial width of ring section 92 , indicated at wr , is determined so that the radial differential between y and wr is deliberately greater than the radial differential between x and wp , as much as double , but still small in absolute terms . each ring section 92 is also axially thinner than retention groove 84 but still thick enough such that it is not inherently resilient or flexible , especially given the fact that it is integrally molded continuously along the relatively large circumferential length of an annular section 90 . still referring to fig1 - 17 , the adjacent annular sections 90 are joined and integrated by cross bars 94 , each of which is approximately half as long as the distance z defined above , and with a thickness t that is slightly less than rs as defined above . here , too , however the radial differential between rs and t is greater than the radial differential between x and wp . since the cross bar 94 is molded integral to the adjacent annular sections 90 , its inner surface can be tightly controlled so as to have only a very slightly greater diameter than the inner surface of the adjacent annular sections 90 that it joins , even as little as 0 . 1 mm more . the smallness of the cross bar clearance proves useful in oil retention during operation , as will appear below . each cross bar 94 is molded with a narrow , axially extending slot 96 that runs almost to its , creating a basic u shape . as noted above , the total circumferential length of the annular sections 76 bounded by the slots 96 is large , and the total circumferential width of the slots 96 is conversely small . each slot 96 is only about one to three degrees wide , just wide enough to provide a necessary mounting flexibility described below . the outer surface of each cross bar 94 is molded with a reaction ear 98 that is shape matched to a cam hook 78 , while the remainder of its outer surface is shape matched to a pad 80 . in addition , in the embodiment disclosed , the axially opposed inner surfaces of each cage half annular section 90 also has an arcuate slot 100 , for a purpose described next . referring next to fig1 and 19 , the wedging elements comprise a plurality of pairs of cylindrical rollers 102 which , end to end , fit within the space z defined above . each pair of rollers 102 fit within a roller control car , indicated generally at 104 , which , as the name implies , surrounds , holds and guides the rollers 102 as the move between the races 62 and 64 . at each side of car 104 , a shape matched guide rail 106 is provided to fit within a respective slot 100 between the cage halves 86 and 88 . each control car 104 is paired with a compression , leaf type energizing spring 108 , which provides a wedging bias to a respective car 104 and its rollers 102 . the cars 104 and cage halves 86 and 88 are assembled and installed as described next . referring next to fig2 through 24 , the installation of the cage halves 86 and 88 to the cam race 64 and ultimately between both races 62 and 64 is illustrated . initially , one cage half or the other ( cage half 88 as shown ) is installed to the outer , cam race 64 by indexing it until the reaction ears 98 &# 39 ; register with the cam hooks 78 and the pushing it axially inwardly , as shown in fig2 . the reaction ears 98 &# 39 ; slide inside and along the cam hooks 78 until the ring sections 92 &# 39 ; engage and are forced radially inwardly by the pilot surface 82 . although the ring sections 92 &# 39 ; are not themselves flexible , they need not be , since the entire cage half 88 is able to contract radially inwardly , because of the radial flexibility created by the slots 96 &# 39 ;. as the stiff ring sections 92 &# 39 ; are forced radially inwardly , the slots 96 &# 39 ; close up , bending downwardly about the end of the cross bars 94 &# 39 ; as shown in fig2 . once the rings sections 92 &# 39 ; have moved inboard of the pilot surface 82 , the ring sections 92 &# 39 ; shift radially outwardly and seat into the retention groove 84 as the cage half 88 re expands to its original shape , as shown in fig2 . the cage half 88 is self seating and aligning , without the need for a jig or tool . next , the control cars 104 , loaded with rollers 102 , slide onto each cam ramp 76 with their guide rails 106 inserted into the arcuate slots 100 &# 39 ;. then , a spring 108 is loaded between each control car 104 and opposed cross bar 94 , after which the other cage half 86 is installed identically to cage half 88 , as shown in fig2 . as seen in fig2 , cam race 64 now has both cage halves 86 and 88 installed thereto , with the springs 108 and cars 104 captured axially between , completing clutch 60 on cam race 64 . the ends of the respective cross bars 94 - 94 &# 39 ; end up substantially abutted , but need not be physically tied together , since each cage half 86 and 88 is independently retained to race 64 . after installation to cam race 64 , the outer edge of each cross bar 94 - 94 &# 39 ; fits closely against a respective cam race pad 80 , but the inner edge has a clearance δc from the inner edges of the adjacent arcuate sections 90 which , as noted above , is very small at about 0 . 1 mm . the inner surfaces of the rollers 102 rest slightly radially inboard of the ultimate location of the pathway 72 . referring next to fig2 and 26 , the next step is to install the pathway race 62 inside of the rollers 102 by pushing it axially inwardly with a slight clockwise ( from the perspective of fig2 ) twist to roll the roller pairs 102 up the cam ramps 76 and compress the springs 108 . post installation , as best seen in fig2 , the outer surface of the reaction ears 98 - 98 &# 39 ; closely engage the cam hooks 78 , and the outer surfaces of the cross bars 94 - 94 &# 39 ; closely engage the pads 80 . therefore , every wedging space as defined above is substantially enclosed , but for the small cross bar clearances δc on two sides and the small pilot clearance δp on the other two sides . there is a radial mounting clearance δmr associated with the ring sections 92 - 92 &# 39 ;, equal to the radial differential between y and wr described above , and a roughly comparable axial mounting clearance , δ mc , as well . relative to the radial mounting clearance δmr , the pilot clearance δp ( the radial differential between x and wp as defined above ) is deliberately made smaller only approximately 0 . 25 mm . the cross bar clearance δc assures that the inner surfaces of the cross bars 94 - 94 &# 39 ; do not ride on the pathway 72 and do not interfere with the riding of the inner surfaces of the annular sections 90 - 90 &# 39 ; on the pathway 72 . referring next to fig2 and 28 , the operation of clutch 60 is illustrated . when the races 62 and 64 over run , the inner and outer edges of the annular sections 90 - 90 &# 39 ; run close to the pathway 72 and pilot surface 82 respectively , given the small radial pilot clearance , thereby maintaining close concentricity between the two races 62 and 64 . concentricity maintenance is not interfered with by any other cage structure , because of the larger mounting clearance δmr ( larger than δp , and because of the cross bar clearance δc . the large total proportion of the circumference of pathway 72 subtended by the annular sections 90 - 90 &# 39 ; assures that there is more than adequate contacting surface area for load support and concentricity control , even though the cross bars 94 - 94 &# 39 ; do not ride on pathways 72 . oil under pressure flows radially out through the passages 74 and between the annular sections 90 - 90 &# 39 ;, forcing them axially outwardly . the pressure bearing axially outwardly against the inner surfaces of the annular sections 90 and 90 &# 39 ; forces the outer faces of the ring sections 92 - 92 &# 39 ; axially outwardly and tightly against the radially overlapping outer surfaces of the retention grooves 84 . because of the large total surface area of the flat ring sections 92 - 92 &# 39 ;, which is less than 360 degrees only to the extent of the total open area represented by the fourteen narrow slots 96 - 96 &# 39 ;, most of the potential leak path past the pilot surfaces 82 is blocked . the higher the pressure , the tighter the seal created , and the relative axial thickness of the annular sections 90 - 90 &# 39 ; prevents any significant outward buckling . likewise , the inherent stiffness of the ring sections 92 - 92 &# 39 ; prevents them from being blown out of the retention grooves 84 . retention is much stronger than that provided by the much smaller surface area of the barbs 54 - 54 &# 39 ; described above . while the wedging spaces are well enclosed on all four sides , some oil is able to leak out axially to the sides through the radial pilot clearance δp , but this is needed to assure that sufficient lubrication is fed between the inner edges of the annular sections 90 - 90 &# 39 ; and the pathway 72 , as indicated by the arrows in fig2 and 28 , when the clutch 60 is over running . the only pressurized oil able to leak out directly would be that which was forced directly into the narrow slots 96 - 96 &# 39 ;, to the extent that they align angularly with the inner oil passages 74 , an event minimized by the narrowness of the slots 96 - 96 &# 39 ;. oil otherwise trapped in the wedging spaces and between the axially opposed annular sections 90 - 90 &# 39 ; could indirectly escape , through the cross bar clearances δc , into the adjacent slots 96 - 96 &# 39 ;. however , that leakage can be minimized , since δc can be minimized while still assuring no contact of the cross bars 94 - 94 &# 39 ; with the pathway 72 , and thus no interference with the concentricity control provided by the close pilot clearance δp . in conclusion , the controlled diameter annular sections 90 - 90 &# 39 ;, in conjunction with the large surface area integral ring sections 92 - 92 &# 39 ;, provide improved concentricity control , improved lubricant retention , and improved mechanical retention , all in an easily installed package , with no compromise among the three improved features .