I have never heard foam tires squeal. It is most likely something rubbing that shouldnt be. TRC tires are wider than JACO's and are not offset more, thus there is more width on the inside. So the wheel might possibly be rubbing. Also TRC tires require longer screws than JACO tires, so it might be the screw is rubbing on the bulkhead or something. The diff could also be loose. it could be a number of things. Also check the front, since they require different bearings the new bearings might also be doing something they shouldnt.