referring now to fig1 and 2 , a wheel end a couples a road wheel to a suspension upright for an automotive vehicle , enabling the wheel to rotate about an axis x . the wheel end a includes a housing 2 that is bolted to the suspension upright , and a rotatable hub 4 to which the road wheel is secured , an antifriction bearing 6 between the housing 2 and the hub 4 to accommodate the rotation , seals 8 at the ends of the bearing 6 , and a speed sensor 10 fitted to the housing 2 . the housing 2 encloses the bearing 6 and at its ends has end bores 16 that receive the seals 8 . both are pressed into their respective end bores 16 . the housing 2 also has an oblique bore 18 that receives the speed sensor 10 . the hub 4 has a drive flange 20 located beyond the outboard end of the housing 2 and a spindle 22 that projects from the flange 20 into the housing 2 . the spindle 22 is for the most part solid , and its end is turned outwardly in a roll forming procedure to provide a formed end 24 that captures the bearing 6 on the spindle 22 . the bearing 6 includes two outer raceways 30 that are machined into the housing 2 and two inner races in the form of cones 32 that are fitted over the spindle 22 of the hub 4 , with each having an inner raceway 34 and a thrust rib 38 at the large end of its raceway 34 . in addition , the bearing 6 has rolling elements in the form of tapered rollers 36 that are located in two rows between the inner and outer raceways 30 and 34 . the rollers 36 along their tapered side faces contact the raceways 30 and 34 — there being line contact — and at their large end faces bear against the thrust ribs 38 of the cones . the rollers 36 are on apex , so pure rolling contact exists between the rollers 36 and the raceways 30 and 34 . one of the cones 32 has an extension 40 that abuts the other cone 32 , and the length of the extension controls the setting of the bearing 6 . it should be slight preload . the extension 40 of the one cone 32 carries a tone wheel 42 that is monitored by the speed sensor 10 . being pressed over the spindle 22 of the hub 4 , the cones 32 rotate with the hub 4 at the same angular velocity as the hub 4 , and the same holds true for the tone wheel 42 , which is pressed over the extension 40 on the one cone 32 . the seals 8 fit into the end bores 16 ( fig1 ) with press fits and surround the thrust ribs 38 of the two cones 32 . here they establish dynamic fluid barriers which isolate the interior of the housing 2 and bearing 6 that is in it . on the other hand , the inboard seal 8 may be replaced by an end cap 46 ( fig2 ) that is pressed into the inboard end bore 16 . for the end cap 46 to be effective , the spindle 22 should not be hollow . the sensor 10 includes a barrel 50 that fits into the oblique bore 18 of the housing 2 and projects toward the tone wheel 46 that revolves with the bearing cones 32 and the hub 4 . indeed , its end lies close to the rotating tone wheel 42 . the sensor 10 also includes a head 52 that lies outside the housing 2 , yet is joined to the barrel 50 so that the barrel 50 and head 52 are an integral unit . the sensor 10 contains electronic components that are completely encased and embedded in the barrel 50 and head 52 , and they enable the sensor 10 to monitor rotation of the tone wheel 42 and produce an electrical signal that reflects the angular velocity of the tone wheel 42 . that signal is delivered to a cable 54 that is connected to the head 52 through a boot 56 and leads to a processor at a location remote from the wheel end a — a location generally free of moisture and other contaminants that might damage electronic components such as those in the sensor 10 . the cable 54 contains leads that actually transmit the signals and a sheath that surrounds the leads . enough space exists between the wall of the sheath and the enclosed leads to enable a fluid to flow through the cable 54 . referring to fig3 - 4 , the barrel 50 of the sensor 10 fits snugly into the oblique bore 18 of the housing 2 , and an o - ring seal 58 located between the barrel 50 and the wall of the bore 18 excludes contaminants , including moisture . the sensor 10 contains a vent channel 60 that at one end opens out of the barrel 50 inwardly from the o - ring seal 58 , so that here the channel 60 communicates with the interior of the housing 2 where the bearing 6 is located . the other end of the vent channel 60 opens into the boot 56 which is in turn is in communication with the interior of the sheath for the cable 54 . the opposite end of the sheath is vented to the atmosphere at the location that is generally free of contaminants . thus , the interior of the housing 2 , where the bearing 6 is located , is vented to the atmosphere through the sensor 10 and through the cable 54 . as shown in fig5 - 6 , a modified sensor 70 is similar to the sensor 10 , but lacks the vent channel 60 in its barrel 50 and head 52 . it does have a flange 72 that lies over the exterior surface of the housing 2 and it contains a hole 74 that aligns with a partially threaded bore 76 in the housing 2 . the bore 76 lies parallel to the oblique bore 18 and like the oblique bore 18 passes from the exterior surface to the interior surface of the housing 2 and thus communicate with the interior of the housing 2 and the bearing 6 . the threads of the threaded bore 76 extend inwardly from the exterior surface that the flange 72 overlies . the hole 74 in the flange 72 of the modified sensor 70 receives a cap screw 78 , which threads into the bore 76 in the housing 2 and secures the sensor 70 firmly to the housing 2 . the cap screw 78 in turn has a head 80 that overlies the flange 72 of the sensor 70 and also a small diameter hole 82 that extends axially through the screw 78 from one end to the other . apart from that , the sensor 70 has a cap 84 that fits over the head 80 of the screw 78 , effecting a seal with the head 80 , and a connecting tube 86 that leads from the cap 84 to the boot 56 at which the cable 54 enters the sensor 70 . at one end the tube 86 communicates with the interior of the cap 84 and the small diameter bore 82 in the screw 78 . at its other end , the tube 86 communicates with the interior of the boot 56 and the interior of the sheath on the cable 54 . thus , the interior of the housing 2 and the bearing 6 within it communicates with the interior of the sheath on the cable 54 through the vent channel formed by the bore 82 in the screw 78 , the interior of the cap 84 that is over the head 80 of the screw 78 , and the tube 86 that connects the cap 84 with the boot 56 of the cable 54 .