My buddy who died a few years ago had a rack and pinion on his T bucket, and it never really worked out well. His was mounted to the frame, which by all accounts is not the way to do it, as the front end will "steer" as the car rises and falls.

As for the ones mounted to the axle, you have hit the problem on the head. How do you make the steering shaft slide in and out of the steering rack as the car bounces up and down? I don't have that answer.

Someone will probably cite that new steering setup where they use essentially 1/2 of a rack that is bolted to the frame rail, and it moves a drag link to steer the car. But that setup is really no different than a conventional box, in as much as it acts to simply move the rod in and out. A true rack, on the other hand, mounts in the center of the axle and acts as the tie rod, except it is controlable with the steering wheel.

I think the fix for jjpop's problem is what bob suggested. Use a panhard bar, or a dead perch to keep the cross steering from moving the axle from side to side.

Don