Final drive failure

Discussion in 'Transmission' started by doc2nd2, Jun 10, 2011.

  1. doc2nd2

    doc2nd2 Member

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    I have ran into a problem with stripping out final drive pulleys. Both were from Belt Drive Ltd. and 7073 aluminum, made in USA. I am having an Andrews steel one installed now. Anybody ever had final pulley strip out, and if so, ever find a cause for it?
     
  2. Breeze3at

    Breeze3at Well-Known Member

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    A dim memory, says there was a problem with drive pullys in the late '80's. Seems it was the locking nut coming loose and allowing pully to wobble the splines out? Sorry, but it's real cluttered in that part of my brain. :newsmile011:
     
  3. Jack Klarich

    Jack Klarich Expert Member

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    LOL, your memory is fine, The MOCO did have issues with a lot of 5 speeds, The pulleys would come off, have seen it on Sportsers too, The MOCO came out with new and improved locking set up, I think the aftermarket lagged on this one thinking they had a good product
     
  4. doc2nd2

    doc2nd2 Member

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    Right guys, the locking for the fina;l pulley nut was a simple allen head bolt to prevent the nut from backing off. The 2 I replaced had the new system with the plate that bolts on in 2 points and is notched to hold the nut in place, well, the nut was there but the pulley teeth gave way on the final output splines. I feel ya Breeze, i got alot of clutter too, need to be on that show "Hoarders" in my head!

    BTW thanks for the input. Mine is a 90 and that confirmed that there is problems and not just me.
     
    Last edited by a moderator: Jun 11, 2011
  5. karlsbike

    karlsbike Active Member

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    Not only did they improve the nut locking arrangment, but the pulley itself was made wider at the splines. This meant a more stable arrangement less prone to wobbling loose damaging the main drive gear splines. The good thing was that the new (1993-up or so) pulley fit straight onto older scoots like mine and yours. I did the change about 10 + years ago, and it is still good.

    I replaced it this winter as I put 6-speed internals into my old tranny case, and the pulley that came with it seems to be even further improved with the locking plate now being integral with the nut itself. The only thing I don't like with this is that it leaves less depth for the large socket (1 3/16" if memory serves me right?) and you need to be careful keeping the socket straight while tightening the thing.
    The pulley itself is much lighter than stock as the web of the pulley is aluminium while both the central splined part and the outer part with the belt teeth are steel. To me, this seems to be the best of both worlds, so to speak...
    In this picture you can see it.

    Trans pulley.jpg
     
    1 person likes this.
  6. TQuentin1

    TQuentin1 Well-Known Member Staff Member Moderator

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  7. karlsbike

    karlsbike Active Member

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    Thanks for the link - I do recall that you've been thru' an ordeal with your tranny. It appears that the pulley has not been properly seated on the main drive gear splines, causing too little nut thread engagment and consequensely thread failure. Looking at pictures of mine, I believe I have better engagement although I would prefer that the main drive gear threads were visible past the nut after tightening. This tells me that the deisgn is not optimal, and there should be sufficient room in there for a slightly longer threaded part of the main drive gear for a deeper nut...