79 Bay, worm and roller steering box repair

Discussion in 'Steering, brakes & Suspension' started by rstucke, Mar 8, 2015.

  1. rstucke

    rstucke Well-Known Member

    Messages:
    473
    Location:
    Wamberal NSW AUS
    I’ve read with some disbelief that these boxes can’t be at least partially repaired. According to the manual a seal replacement and cross shaft adjustment is all that can be performed and preload on the worm can be measured but not adjusted. Boxes for LHD’s won’t fit RHD’s because they are mirror opposites and good second hand boxes are scarce. Some have said certain recon boxes were available but were crap (wearing fast and leaking oil) and very expensive. I’ve repaired more steering boxes than I can remember in my working life and now that I’m retired and have a late bay to restore to stop me going senile (although I think I’ll be a dribbling mad man by the time I’ve finished it), I thought I’d take up an obvious challenge and find out why these things can’t be repaired. The box in my bay wasn’t totally shot but wasn’t that good either. The adjustment on the cross shaft was down too far and there was plenty of back lash. It had oil in it but you can see from the picture that it wasn’t good and there wasn’t a lot of it. I’ve put in a fair effort to repair the beam (another thread, a big thankyou to the people who showed me where to source the inner bushes) and putting in a less than serviceable steering box would not do it justice.
    P2260019.jpg P2260020.jpg

    Anyway I was successful in repairing the steering box and in doing so found some interesting practices by ZF in there manufacture that do not make repairing them a walk in the park. I have documented the process that I used and intend to post it here. If you are interested read on, if not thanks for reading this far.
     
  2. rstucke

    rstucke Well-Known Member

    Messages:
    473
    Location:
    Wamberal NSW AUS
    So I stripped the box down and had a good look at the parts. Then cleaned and had another good look at the parts. P2270021.jpg

    The cross shaft and roller were in surprisingly good shape. Shaft had only witness marks and no scoring (and measured up ok). The roller rotated smoothly with no radial or side play and no scores on the wearing surfaces. This and the worm are the deciding factors that govern the repair. If either the shaft or worm are cactus then it’s not worth the effort. What I have found in most steering boxes is the wear is in the cross shaft bearings mainly. The bearing that the roller rotates on can’t be replaced because of a hardened rivet holding it on the cross shaft but if the shaft is scored it can be ground and oversized bushes used. The bearing and wear surfaces on the worm were in as good a shape as the shaft. These parts are much more heavy duty than the cam and peg (worm and peg) boxes of the earlier Bays and baring a lack of oil the worm and roller should survive.
    The oil showed signs of bronze (a lot)
    The bushes confirmed this. If you look closely the thrust side of the cover plate bush is thin compared to the other side.
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  3. rstucke

    rstucke Well-Known Member

    Messages:
    473
    Location:
    Wamberal NSW AUS
    When you adjust the cross shaft you are pushing the shaft further onto that worn side of the bush as the roller on the shaft engages further into the worm to take up the slack. Move the shaft far enough and the seal at the other end will start to leak oil as it will no longer be concentric.
    Most manufacturers use crowded needle rollers in a thin shell in these areas but replacing them with such is out of the question because the shaft is not hardened enough
    You would think it would just be a matter of pressing the old bushes out and replace them with new ones. This is where ZF used an interesting practice in there manufacture. They place the bush in a dye and cast the aluminium housing around it burying the outer part of the bush in the housing. I had to machine these suckers out which presented a whole new problem, no place to hold the cover plate in the lathe concentric to the bush. If I get this off centre or skewed then game over as the box will lock up once reassembled. The pictures show the jig I made to overcome the problem. It basically mimicked the housing and allowed me to reverse the cover plate in the lathe to gain access to the bush.
    P3040001.jpg P3040003.jpg P3040004.jpg P3040005.jpg P3040006.jpg P3040007.jpg
     
  4. rstucke

    rstucke Well-Known Member

    Messages:
    473
    Location:
    Wamberal NSW AUS
    The next step was to prepare the outer surface of an unfinished bronze bush to be a press fit into the cover plate I then pressed it into the housing with a bit of heavy duty Loctite.
    P3040008.jpg
    P3040009.jpg
    P3040010.jpg

    A bit more machining on the inner surface for a 0.1mm clearance fit.
    P3040011.jpg P3040012.jpg P3040013.jpg
     
  5. rstucke

    rstucke Well-Known Member

    Messages:
    473
    Location:
    Wamberal NSW AUS
    Next step was replacing the bush in the housing, more challenges similar to the cover but with the added benefit (not) of holding the housing at one end and machining the other end. I made a heavy duty mock cover out of cast iron that the lathe could hang onto. A very light cut proved its’ concentricity before machining the bush out. You can see the pimples of aluminium that hung onto the dimpled bush in the pic.
    P3040013a.jpg P3050014.jpg P3050019.jpg P3050020.jpg
     
  6. rstucke

    rstucke Well-Known Member

    Messages:
    473
    Location:
    Wamberal NSW AUS
    Machined another bronze bush, pressed it in (more Loctite) and machined it out (0.1mm clearance). The seal area was machined also. Went from a 38x28x7 seal to a 40x28x7. The idea was to keep the seal absolutely concentric to the shaft to avoid leaks.
    P3050021.jpg P3060002.jpg P3060004.jpg P3060005.jpg
     
  7. rstucke

    rstucke Well-Known Member

    Messages:
    473
    Location:
    Wamberal NSW AUS
    I put the cross shaft in the housing and the cover plate on and bolted it up and all was good. Smooth, no side play and no tight spots. Now to put it back together. Angular ball bearing races that fit are available from bearing services, so are the outer shells. The inner race is part of the worm.
    Worm preload first. ZF uses a simple arrangement to maintain preload in the form of a cupped washer. The washer is like a strong spring it deforms under the force of its retainer when bolted up and pushes on the outer shell of one of the worm bearings which preloads the worm. There is a shim under the retainer (not shown) that controls the initial preload in manufacture. All things being in good shape it was only a matter of measuring the preload to verify the spec. Here comes another problem. The spec is 8-12 kg/cm but this is with the cross shaft installed and moving through the centre section of the worm. I would suggest less or at least on the low side at this stage (with no cross shaft installed). An example I remember is a ke30 Toyota 4 to 6 kg/cm no cross shaft, 8 to 11 kg/cm with cross shaft installed.
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  8. rstucke

    rstucke Well-Known Member

    Messages:
    473
    Location:
    Wamberal NSW AUS
    The best way to measure this is to use a pulley with a known radius, wrap a cord around it several times, attach it to the worm shaft via a grub screw and pull the cord with a spring scale graduated in kg. Note the steady reading as you pull the spring scale then calculate the kg/cm. My pulley had a 75mm radius to the bottom of the V. I pulled close to 800 grams so 0.8x7.5 is around 6kg/cm. Good enough for me and I checked it after the cross shaft was installed (close to 10 kg/cm). The pic doesn’t show the actual reading (I was holding the camera, not enough hands).
    P3060009.jpg P3060010.jpg

    The rest is pretty straight forward. New O rings, adjust free play by rocking pitman arm

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    If you got this far thanks for your patience. It took me 16 hours all up over 4 days (not including chasing bits) but I’m a bit slow these days. Anyway if you’re thinking of repairing your late bay steering box you should have a better idea of what you’re in for. By the way not all oils are compatible with bronze. Whatever you use make sure it is compatible with yellow metal (usually stated in the data sheet).
    Good luck guys.
     
    onetrackwonder likes this.
  9. farquire

    farquire Member

    Messages:
    572
    Location:
    newport sydney
    thanks for that,great reading,i could see you making a bit of pocket money by doing these,:)
    cheers mike
     
  10. melissa

    melissa Administrator Staff Member

    Messages:
    14,221
    Location:
    Newcastle NSW
    Great post there. Would you be interested in doing this for others? I would definitely be keen for one for my 75.
     
  11. StevieVW

    StevieVW Well-Known Member

    Messages:
    3,472
    Location:
    Somerset, Tasmania
    Where do we send the boxes and the money?
     
  12. gazman

    gazman Well-Known Member

    Messages:
    1,758
    Location:
    Perth WA
    Haha you're gonna be busy! top work too btw
     
  13. rstucke

    rstucke Well-Known Member

    Messages:
    473
    Location:
    Wamberal NSW AUS
    The thought of repairing endless steering boxes in my retirement doesn't really float my boat. I posted what I did to give an insight to what is involved and to inspire others to take up the challenge. Surely there are those of you with a decent lathe and the ability to complete the task.

    Having said that I would like to prove my theory that the worms and cross shafts survive 36+ years in our boxes, plus mine won't go into service till the end of the year. So I'm prepared to do one or two more so that I can inspect the bits and I can get feedback on how it goes in service.
    Melissa you are just up the highway from me so if you are prepared to remove it or have it removed and get it down to me I'll repeat the process on yours . I don't want any payment but you will have to pay for parts and there are no guarantees your worm and cross shaft are good (but I hope so). Message me your contact details and I'll get in touch.

    ATTENTION
    There is a major concern with removing the large nut on the end of the pitman arm (the pitman arm must be removed to get the steering box out). Do not under any circumstances allow the pitman arm to travel to its' stop in the box while you are heaving on the nut with bar and socket. If you do you can kiss your cross shaft roller and bearing goodbye, instead slip a length of water pipe over the pitman arm and hold it in the middle of its' travel while you loosed the nut.

    Cheers
    Rick
     
    Last edited: Mar 9, 2015
    jason young likes this.
  14. melissa

    melissa Administrator Staff Member

    Messages:
    14,221
    Location:
    Newcastle NSW
    Thanks Rick, I will send you a PM.
     
  15. Mordred

    Mordred Super Moderator Staff Member

    Messages:
    2,622
    Location:
    Penna, Hobart
    Top piece of informative writing and the pics are brilliant. Thank you for the effort.

    Adrian
     
  16. oldman

    oldman Super Moderator Staff Member

    Messages:
    7,708
    Location:
    Avalon Beach NSW
    Brilliant work Rick !!
    As others have posted, you could easily earn a $ from refurbishing these boxes if you chose to.
    Worthy of a Sticky for those that have the skills & equipment but lack the knowledge.
    Well done mate. ;)
    Cheers,
    Mark
     
  17. Anna Bay 73

    Anna Bay 73 Member

    Messages:
    91
    Location:
    Anna Bay
    Great post. In an effort to get decent steering, the best I could do was a second hand box from Nymers at North Belmont where they put together bits from various boxes to get a combination that still has adjustment. Ok but not great. Their advice was that when the adjustment screw is flush with the lock nut, the box is well worn. I had a look at the adjustment screw on about 20 kombis at the last Old Bar event and most had two or three threads showing, not many with more and a few sunk lower than the lock nut. I did take my old box apart and was impressed by the quality of the shaft and roller. When I saw the wear in the bushes I new it was well beyond anything I could do to repair. The Stokers Siding parts people were importing used right hand drive boxes from the UK for around $500 from memory and the Just Kampers guy at Old Bar said his dad was reconditioning Kombi steering boxes. This post lets us see whats involved and why it's going to cost!
     
  18. rstucke

    rstucke Well-Known Member

    Messages:
    473
    Location:
    Wamberal NSW AUS
    hi Anna bay 73
    I'm looking at some second hand boxes to do up..
    If you want your box repaired pm me and organize to get it down to me.
    I'm re conditioning my 79 bay at the moment but can find the time to do your box. Charge for parts only.
    Cheers
    Rick
     
  19. Anna Bay 73

    Anna Bay 73 Member

    Messages:
    91
    Location:
    Anna Bay
    Hi, a very generous offer, will send you a PM.
     
  20. AnnaBay73

    AnnaBay73 New Member

    Messages:
    29
    Location:
    Australia
    Hi, I took up Rick's offer. I got to check out his resto underway and he is doing a fantastic job. I refitted the box this weekend and had a quick drive between the heavy rain. Came back with a big smile, steering lighter and more responsive, with big decrease in free play. I will report again after more testing.Big thanks to Rick.
     
    1500king and cbus like this.

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