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  • ZF steering box

    Guys,

    I have mentioned quite recently the fact my ZF steering box over the past 10 years or so has leaked slightly after a run and leaving the
    car for a few days in the garage. Just a small circle of oil every time. I have presumed it was from the bottom seal and after all it is 57 years old.

    Now for my obvious lack of experience, of these boxes. I read recently on Phil's thread from memory his comments on the ZF and also Jack's comments which I have now found so very useful.

    1). For 47 years I have checked my ZF steering box oil level and as mentioned above have had to make sure I replenished it every 3 months or so after these leaks.

    2). I know now its stupid, but for all these years I replenished the missing oil with my front wheels straight ahead. When you look down into the filler hole you see a round flat steel type washer that almost stops free delivery of oil and you no real indication of the level.

    3). When I asked Jack how do you drain the old oil ( its never been drained or fully replaced in 57 years ) and there is no bottom drain hole, he wrote back and advised suction it out.

    4). I thought how can I do that, there is no room to get a pipe into the hole. I then using a medical syringe and a extension pipe with a small diameter length on it to reach the bottom was still perplexed!

    5). So I looked at the schematic in my workshop manual and no specific info on how to drain is given in the 356A supplement. Suddenly I had one of those weird moments of clarity! I went to steering wheel and turned it nearly full lock. Low and behold the filler hole was clear of worm and peg obstruction!!

    6). I then suctioned out the blackest SAE 90 gear oil from the box and replaced it with new oil.

    7). Now guys, ever since I topped it up to the level they advise it had run with no leaks what so ever!! This has really surprised me and I have waited some to tell you this.

    I want to thank Jack particularly for his advice. Maybe some other person lacking something like me, has tried to fill it with wheels straight ahead Maybe lucky the seal is okay, I do not want the job of stripping it down.

    Roy

  • #2
    Makes perfect sense Roy. I can see how the Peg carrier would interfere with the filler hole in that position. Like it when the solution is simple.
    Click image for larger version

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    There is one oil drain in these boxes, I know that one(maybe both)of the forward tapped holes for the mount studs does breach the boxes interior. So if you could back one of them out it could be your oil drain.
    Justin Rio

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    • #3
      Roy

      I think the manual calls for a specific amount of oil, which as I recall amounts to 1 cup. Will have to check my notes. Anyway, don't know how much you added, but possibly it was being overfilled before. Just a guess. Hope it stays leak free for you Roy.

      Phil

      Comment


      • #4
        Phil,

        The amount of oil required is stated as 250 millilitres. This equals 8.45 fluid ounces. Likewise one cup that you mentioned equals 240ml.

        I know from cooking programs on TV you use cups for measurement, we don't seem to do that here. Every bottle of washing up liquid for example has 750ml in accordance with EU standards. I am used to pints, gallons, etc but even there your gallon in different to ours in the UK. All our petrol ( sorry gas ) stations are supplying litres I just go filling till the fuel cut off comes into operation. They didn't ask me if I wanted to change to metric. Likewise can you imagine the problems for me fully conversant with imperial measurement as a toolmaker then working to 0.0001 inches and then having to change to microns! I have many micrometers, rules, verniers, you name it, all redundant except if I emigrated to your country. Tooling manufactures must have had good time making metric tools to replace all those now hidden in the back of my tool box!!

        Anyway to get back to the ZF box,

        1). Justin never thought of that drainage possibility! Although when that filler hole is clear, and if your suction tool works well its amazing how well it works to even suck out the sludge from the bottom of the box.

        2). This is important! People have said without explanation the box should not be overfilled. Now that is something I must have been doing with the worm obstucting the entry hole. You could not see any level only when the oil tended to drip out of the hole. I think then with the box totally full fast movements of the steering wheel POSSIBLY?? imparted pressure to the bottom seal forcing oil out???

        3). When that entry hole was clear so easy to see the level.They said as the oil should just be before tapped entry hole my measured 250ml came exactly to this point.

        I do wonder if other people have been overfilling and possibly the seal is not at fault??

        This year my starter motor runs like new and my garage floor is dry of SAE 90 gear oil. Life is great

        Roy

        Comment


        • #5
          Roy, checking/adding oil is part of routine maintenance. How would anyone know if it is being overfilled? Drain and refill the box each time? I have my doubts. I presume that the location of the fill plug, coupled with the angle of the box, would disallow overfilling of the box if done so with the car on level ground, much like the gearbox, but I have not checked the factory manual.
          Justin, interesting observation of the open stud hole. I am not aware of this, and have had many instances of various studs being pulled out on ZF due to bound nuts, and no fluid draining. Maybe the right one has yet to give. Are you sure is not a T0 or T1 thing with the VW box?
          Jack (analog man from the stone age)

          Comment


          • #6
            Come to think of it I might have that feature confused with a Type 1 box Jack.
            Justin Rio

            Comment


            • #7
              Jack,

              With the wheels straight ahead and the filling hole obstructed by the worm you cannot see the oil lever at all. I could never understand how reading the factory manual any level could be maintained accurately.

              Only when turning the steering wheel on full lock can you see exactly the level of oil you are putting in. Now its easy to see if any oil is lost. All these years and I never twigged why

              My question is though as I could not previously see a level to work to, I just filled till I could not get any more oil in it. It almost overflowed the filler hole. Now after replacing the filler cap could then, a form of hydraulic pressure push the oil in the overfilled box past the bottom oil seal?

              This is what you get when DIY people get involved thinking its easy to do and not thinking what moves in that box?

              Roy

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