I don't think this is the issue but there is a Bolt at the bottom of the Steering Box close to shaft where the steering arm attaches. It will have an aluminum or copper cursh washer.

With the Wheels Pointed forward (engine off) when you remove the Bolt/plug (some Oil will drip out) look past the threaded area and you should be able to see a hole. That hole is where a special taperd check bolt goes to center the Steering Box. However, you are just looking to see if you can see it.

If you cannot see it then have someone turn the steering wheel slowly (enging off) until that inside hole lines up with the threaded bolt hole. When it does look at the wheels. If the wells are not straight forward that means the arm is mounted in the wrong position (I don't know if that is possible).
Keep the Stering box with that hole lined up with the threaded hole and pull of the Arm and straighten the front wheels and re-install the arm so that the wheels are straight. Then everthing should be centered.

Note that when everthing is centered you steering wheel also should be centered.

Member Marturo has that he rebuilds steering boxes. You could also ask him for info.

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84 300D, 82 Volvo 244Gl Diesel