James, There are several adjustments on the steering system and they have to be done in a specific order.

Steering shaft must be in the locked position.
Steering wheel must be straight
The shaft going into the steering box must have the correct preload on the bearing to prevent end play.
The adjustment screw must be adjusted so there is a slight tight spot at the exact center of travel.
The steering box must have a locking bolt installed to keep the box centered during instillation.
Last but not least, a good alignment AFTER all the above adjustments are made.

I am thinking that somewhere along the line something was not adjusted correctly and the boxes were just installed the way the old one came out. Then the alignment was done to make the steering wheel straight when the car was going down the road.

The first few things can be easily checked. Just remove the key and turn the steering wheel until it locks. Is the steering wheel straight? It should be.
Next unlock the steering and have someone turn the steering wheel back and forth through the play. You look very carefully at the shaft going into the steering box and see if you see any in/out motion. If you do, the box is not adjusted correctly.
The next step will be to remove the drain bolt from the steering box (you will lose some fluid) and with the steering wheel straight you should be able to see a hole up in the piston that moves back and forth in the box. This is where you insert a pointed bolt in the drain hole to hold the box in the centered position. At this point the front wheels should be straight.

The whole point of all this is that if the box is not centered when the car is moving straight, then there will be play in the steering.

I just did the reseal on my 500 that has a 420 steering box and went through all of these adjustments and found the steering shaft was not correct. It didn't lock with the steering wheel centered. I locked the steering shaft and changed the steering wheel so it was correct. I did all the adjustments to the box with it on the bench. Installed the centering bolt. Installed the box. Had my alignment man adjust the front end using the lock bolt in the box. It is a different car. One problem I had was in gusty winds, the car was hard to handle. Now you can't even feel them. It doesn't pull at all. Life is good.

Sorry for the long post. I am just trying to help. If the person installing the boxes isn't aware of all this, you will never get the problem fixed.


Paul

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84 500 SEL (307,xxx miles)