speedo and odometer probs.

got an '03 F250 SuperDuty Lariat 7.3 Turbo DSL 2WD...and just recently the speedo and odometer stopped working. the odometer still lights up w/ the last recorded miles...speedo doesnt work at all.....and all the other gauges and warning lights work fine. abs light is on...however not exactly sure how to retrieve the codes. i keep hearing how the speed sensor on the differential could be a prob so i've changed it...still same prob. is there another sensor that the odom & speedo runs off of that im missing? or could someone explain to me how to pull abs codes

you should have one one the rear diff. thats the one the speedo uses and maybe the rear antilock.