Manual steering gearbox leak

[ironmaiden]

My 1968 280SL manual steering gearbox leaks oil from the steering shaft at the steering (Pittman) arm.  From my reading and discussion with others, the options to stop the leak are to, (1) purchase a reconditioned gearbox for approximately $1000, or (2) to completely disassemble the gearbox and install the 2 new seals and a new gasket on the gearbox housing cover.  Both options involve removing and reinstalling the gearbox on the car.  If the gearbox is disassembled, the end float of the worm and the pressure on the steering shaft must be readjusted following complex procedures.

It seems to me that it just might be possible to remove the Pittman arm with the gearbox on the car, pick out the old leaking seal with an awl, and then drive in a new seal using a suitable pipe drift.  Has anyone ever tried this?  If successful, it would save a lot of work and money.

[Benz Dr.]

You have an hour or two to loose by trying it. Big question is; will the pitman arm come off easily - sometimes they don't.

[Tyler S]

Looking at this it looks like you might be able to remove the bottom cover via the 6 allen bolts after you get the pitman arm off. It looks like there are needle bearings in there as well. With the cover off and on the bench it would be a lot easier to replace the seal and grease the needle bearings to hold them in position.
You are definately going to need a puller For the pitman arm

[ironmaiden]

You may be looking at the power steering gearbox which has the 6 allen bolts holding a bottom cover to the housing.  From my books there are two versions of the manual steering gearbox, both having the steering shaft installed from the top, via a removable top cover, thru a hole in a large boss at the bottom of the housing.  One of the versions has gear teeth on the steering shaft while the other version has an arm on the steering shaft with a ball cup that engages the steering nut on the worm.  I believe I have the latter version. 

[Tyler S]

Yep, your right, I missed the "manual" key word.
You might be able to screw a drywall screw into the shell of the old seal, then use pliers to pull it out.

[ironmaiden]

I got the Pitman arm off.  Looking from underneath the car, the seal looks perfect from the outside.  Just sitting, it does not leak.  The oil drips only after driving the car.  Since the manual steering gearbox is not under pressure, I don't understand why it doesn't leak also while just sitting.  Could there be something else other than the seal that would cause the box to leak only after driving the car?

[Tyler S]

The outer part of the seal is just a dust shield. The inner lip that you cant see is what seals the oil in. When you drive it there is movement and heat. When it gets warm the fluid expands. It could also be the outer edge of the seal that is leaking.

[ironmaiden]

Progress Report

With the gearbox on the car, I attempted to drill into the center of the lower seal ring and use a small sheet metal screw to pull on, but the screw broke out of the metal part of the seal without budging the seal.  So I decided to take the gearbox out of the car so I could see what I was doing.  With the gearbox on the bench,  I drilled very near the OD of the seal, holding the drill at a slight inward angle (towards the shaft center).  This time the screw got a better purchase on the metal part of the seal, and I was able to use a pair of wire cutters against a screwdriver resting on the housing to pry up on the screw and pull the seal out easily.  I noticed that the rubber on the new seal was much softer than on the old seal, probably due to age and exposure to oil.  So I decided to go ahead and replace the other seal (gearbox input shaft that connects to the steering wheel).

Now I am looking at the coupling that connects the steering wheel shaft to the input shaft of the gearbox.  On my 280SL it is actually a universal joint.  I noticed that one axis rotates very freely while the other axis feels gravely like the bearing is dry or has dirt in it.  Do you know if this universal joint has bearings or just pins?  Should it be replaced or can it be lubricated?  It looks like it would be difficult to remove the upper clamping bolt on the universal joint since it is recessed up inside of a bowl shaped cover attached to the firewall.