Is that hole supposed to be there? I mean, it looks like it.
Once again, fixing someone else problems here and I dont know whats all been done to this truck. Its kinda pissing me off.
Yep, that's a vent hole as the yoke travels back and forth, that's why you need the o-ring, but there's supposed to be a non splined area in the yoke for the o-ring to ride on so it can seal, so that yoke shouldn't have a hole some idiot drilled one, that yoke is used with an output shaft that has one spline missing, the missing spline acts as a vent back into the tail housing, check and see if you have a missing spline on the output shaft, if you do just plug the hole up and you're good to go, if there is no missing spline you'll have to get the proper yoke and use an o-ring, there's also a cup that goes on the shaft too..
Well, I may not be 100% right on the non splined area in the yoke, just looked and I have two of them with holes and they are full splined???..