Switching Manual to Automatic Steering

[twinoakchef]

The previous owner of my 70 280 SL picked up many parts to switch the steering form manual to automatic. Is it just an issue of adding a new gear box and a pump or are there other issues?

[JimVillers]

The interesting issue is the steering shaft.  In my 230SL, it needs to be shortened.  I am not sure about the 250 or 280.  If you decide to do the job, It is easier to pull the pitman arm from the manual box and reuse than removing the tie rods and replacing them undamaged. 

[waqas]

Jim is correct. However, the pitman arm needs to be re-attached at a very specific location relative to the steering box center/straight-ahead position. I find doing this on the bench is far easier that trying to align it under the car.

Also, having a good ball-joint separator has been invaluable, one that separates the ball-joints without any damage to the boots.

If anyone needs to perform surgery on their steering shaft, I have a spare complete 108 sedan shaft assembly. This might allow you to avoid having to make irreversible modifications to your original pagoda shaft.

[Dave Gallon]

The power steering box (and pump) applicable to a 280SL were used on many models of Mercedes from the 1960s and even the 1970s. However, pitman arms are not generally interchangeable. On a 250SL and 280SL, the pitman arm for a manual steering box is a 111 463 25 01. When power steering is fitted, this pitman arm is deleted and a 112 463 16 01 is used. You may find several different pitman arms on a power steering box depending on its source. I would have to do further research to determine which models originally used the 112 463 16 01 but the part number is right on the pitman arm so you can check what you have. The point is that when installing a power steering box from an unknown source, you must insure you have the correct pitman arm. Further, it is not appropriate to remove the pitman arm from a manual steering box and install it on a power steering box.

The steering on 280SL and later 250SL has a collapsible steering column. As such, the steering column does not have to be changed when installing the power steering box on a car with manual steering. The BBB for passenger cars from 1968 describes the procedure for adjusting the length of the steering column to match either the manual or power steering boxes. The 108 steering column has no application in a 280SL

The location of the pitman arm on the steering box is clearly indicated by a mark on the pitman arm and the output shaft of the power steering box. There is no question of the correct rotational position of the pitman arm. However, it is true that when installing the power steering box onto the end of the steering column, the steering column must be in its straight ahead position (as indicated by the mark on the steering wheel end of the steering column) and the steering box must be locked in its straight ahead position. This is required so that the turn signal switch cancels at the correct rotational position of the steering column. Further, the steering wheel must be installed in its straight ahead position (in other words, spokes horizontal) when the steering column is in the straight ahead position. When these parts are assembled correctly, a front end alignment is required so that the car drives straight ahead when the steering wheel is in its straight ahead position.